Preparation and Properties of Certain Fluorine-Containing Esters and Ketones

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P U R D U E U N IV ER SITY

THIS IS TO CERTIFY THAT THE TH ESIS PREPARED UNDER MY SU PERV ISIO N

b y

__________ T u g e n e

e n title d

llo y c e

P re p a re tio n

L 'ils o n

and

P ro n e rtie s

o f

C ertain

F l u o r i n e - C o n t a i n i n g i s t e p s and P e to n e s

COMPLIES WITH THE UNIVERSITY REGULATIONS ON GRADUATION TH ESES

AND IS APPROVED BY ME A S FULFILLING THIS PART OF THE REQUIREMENTS

FOR THE DEGREE OF

D o c to r o f P h il o s o p h y

TO THE LIBRARIAN:-----

IS THIS TH ESIS IS NOT TO B E REGARDED A S CONFIDENTIAL.

PROFESSOR n r

GRAD.

SCH O O L FORM

9 —3 - 4 9 —1 M

CHARGE

PREPARATION AMD PROPERTIES OF CERTAIN FLUORINE-CONTAINING ESTERS AND KETONES

A T h e s is S u b m itte d t o th e F a c u lty of Purdue U n iv e r s ity

by

Eugene Royce W ilson

I n P a r t i a l F u lf ill m e n t o f th e R eq u irem en ts f o r th e D egree

of D o c to r o f P h ilo so p h y Ju n e , 1950

ProQuest Number: 27714108

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is d e p e n d e n t upon the quality of the copy subm itted. In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion.

uest ProQuest 27714108 Published by ProQuest LLC (2019). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346

To my w if e , E v e le n a

ACKNOWLEDGMENT I t i s im p o s s ib le t o name th e many f r i e n d s who have so g e n e ro u s ly c o n t r ib u t e d t h e i r a d v ic e and c o u n s e l.

In p a r tic u la r , I

w ish t o e x p re s s my s in c e r e a p p r e c i a ti o n to P r o f e s s o r E. T. McBee, th e d i r e c t o r o f t h i s r e s e a r c h , f o r h i s a b le a s s i s t a n c e and c o n tin u e d i n t e r e s t th ro u g h o u t t h i s r e s e a r c h and th e p r e p a r a t i o n o f t h i s t h e s i s . I am a l s o in d e b te d t o P r o f e s s o r s W. E. T ruce and N. Komblum and D r. Z. D. Welch f o r t h e i r p e r s o n a l i n t e r e s t and a d v ic e . I w ish to th a n k th e Purdue R e search F o u n d a tio n , F ir e s to n e T ir e and Rubber Company, and A ll i e d C hem ical and Dye C o rp o ra tio n f o r t h e i r f i n a n c i a l s u p p o rt, w ith o u t w hich t h i s r e s e a r c h c o u ld n o t have b een ac c o m p lish ed .

TABLE OF CONTENTS Page ABSTRACT P a r ts 1* and 2 . P r e p a r a tio n and P r o p e r t i e s o f C e r ta in F lu o rin e - C o n ta in in g E s te r s and K e to n e s .......................

i

A ttem p ted P r e p a r a tio n o f D if lu o r o k e te n e ..............................

xv

INTRODUCTION........................................................................ ......... ....................................

1

P a r t 3»

PART I

PREPARATION AND REACTIONS OF ETHYL ACETOACETATE

-TBTRAFLUORO-

I n t r o d u c t i o n ...........................................................................................................

U

P r e p a r a tio n o f E th y l D if lu o r o a c e ta t e D is c u s s io n ....................................................................................................

6

E x p e rtm e n ta l P r e p a r a tio n o f 1 , 1 , 2 , 3 , 3 -P en ta c h lo r o p r o p a n e .............

7

P r e p a r a tio n o f 1 , 2 , 3 , 3 -T e tr a c h lo ro p r o p e n e ..................

8

P r e p a r a tio n o f 1 , 2 - D ic h lo r o - 3 ,3 - d if lu o r o p r o p e n e ..♦

8

P r e p a r a tio n o f D if lu o r o a c e tic A c id ..................................

9

P r e p a r a tio n o f E th y l D i f lu o r o a c e t a t e .............................

9

P r e p a r a tio n o f E th y l a. ,@ ,r ,y - T e t r a f lu o r o a c e to a c e t a te D is c u s s ! o n ....................................................................................................

10

E x p e rim e n ta l

13

...............................................................

R e a c tio n s o f E th y l ci ,o f ,> p ^ - T e tr a f lu o r o a c e to a c e ta te D is c u s s io n D e r i v a t i v e s .......................................................................................

Ill

P r e p a r a tio n o f tX ,ot,y,y—T e tr a f lu o r o a c e to a c e tic A c id .................. .........................................................................

15

P r e p a r a tio n

16

o f 1 ,1 ,3 ,3 - T e t r a f l u o r o a c e to n e ...................

Page R e a c tio n o f E th y l ,> - T e tr a f lu o r o a c e to a c e tic A c id ...........................................................................................

21

P r e p a r a tio n o f 1 ,1 , 3 , 3 - T e tr a f lu o r o ace to n e ...................

21

R e a c tio n o f E th y l oL ,> ,> - T e tr a f lu o r o a c e t o a c e t a t e w ith Anhydrous Ammonia.............................

23

P r e p a r a tio n o f E th y l l- C a r b e th o x y -2 - e th o x y 1 . 1 . 3 . 3 - t e t r a f l u o r o - 2 - p r o p y l C a rb o n a te ...............

23

P r e p a r a tio n o f 2 , 2 , U ,U -T e tra flu o ro -1 ,3 ~ b u t a n e d i o l ..............................................................................

21;

Clemmensen R e d u c tio n o f E th y l « t,,>-T et r a f l u o r o a c e t o a c e t a t e ...........................................................

25

Summary......................................................................................................................

26

PART I I

MIXED ESTER CONDENSATIONS OF ETHYL DIFLU0R0ACETATE

I n t r o d u c t i o n ...........................................................................................................

29

C o n d en sa tio n s w ith A cid C h lo rid e s D is c u s s io n .....................................................................................................

29

E x p e rim e n ta l P r e p a r a tio n o f E th y l 1 -C a rb e th o x y -2 -e th o x y 1 , 1 , 3 , 3 - t e t r a f l u o r o - 2 - p r o p y l C a rb o n a te ...............

33

R e d u c tio n o f E th y l 1—C arb eth o x y —2- e th o x y 1 . 1 . 3 . 3 - t e tr a f l u o r o - 2 - p r o p y l C a rb o n a te ...............

3U

P r e p a r a tio n o f 1—C a rb e th o x y -2-e th o x y 1 . 1 . 3 . 3 - t e t r a f l u o r o - 2 - p r o p y l B e n z o a te .. . . . . . .

35

Page C o n d e n sa tio n s w ith O th e r E s te r s D is c u s s io n ....................................................................................................

36

E x p e rim e n ta l P r e p a r a tio n o f P henyl T r if lu o r o a c é t a t ..........................

37

Mixed C o n d en satio n w ith E th y l C a rb o n a te ...............

38

Mixed C o n d en satio n w ith E th y l T r i f l u o r o a c e t a t e . . . .

38

Summary......................................................................................................................

39

PART I I I

ATTEMPTED PREPARATION OF DIFLUOROKETENE

I n t r o d u c t i o n ....................................

1;1

R e a c tio n o f C h lo r o d if lu o r o a c e ty l C h lo rid e w ith Zinc D i s c u s s i o n ...................................................................................................

U3

E x p e rim e n ta l P r e p a r a tio n o f C h lo r o d if lu o r o a c e ty l C h lo r id e ............

UU

D e h a lo g e n a tio n o f C h lo r o d if lu o r o a c e ty l C h l o r i d e .. .

UU

D e h y d ro h a lo g e n atio n o f D if lu o r o a c e ty l C h lo rid e D is c u s s io n ....................................................................................................

k5>

E x p e rim e n ta l P r e p a r a tio n o f D iflu o ro a c e ty l C h lo r id e .........................

U6

D eh y d ro h a lo g e n a tio n o f A c e ty l C h lo r id e .........................

U7

D eh y d ro h a lo g e n a tio n o f D if lu o r o a c e ty l C h l o r i d e . . . .

U8

P y r o ly s is o f D if lu o r o a c e tic A cid D is c u s s io n ....................................................................................................

U8

E x p e rim e n ta l...............................................................................................

50

p y r o ly s is o f D iflu o ro k e te n e Polym er D is c u s s io n ...............................................................

51

E x p e rim e n ta l.................................................................

51

Page P r e p a r a tio n and P y r o ly s is o f D if lu o r o a c e ty lp h th a l im id e D is c u s s io n ....................................................................................................

52

E x p e rim e n ta l P r e p a r a tio n o f D if lu o r o a c e ty lp h th a l im id e .....................

55

P y r o ly s is o f D iflu o ro a c e ty lp h th a lim id e .........................

56

P r e p a r a t i o n and P y r o ly s is o f 1 ,1 - D if lu o r o a c e to n e D is c u s s io n ....................................................................................................

57

E x p e rim e n ta l P r e p a r a tio n o f 1 ,1 - D if lu o r o a c e to n e ..................................

58

P y r o ly s is o f 1 ,1 - D if lu o r o a c e to n e .......................................

59

Summary............................... BIBLIOGRAPHY...................................................................................................................... VITA

59 60

LIST OF TABLES

H alo g e n -C o n ta in in g A c e to a c e tic E s te r s

i

AN ABSTRACT D ep artm en t o f C h e m istry and P urdue R esearch F o u n d atio n P u rd u e U n i v e r s ity , L a f a y e tt e , I n d ia n a

PREPARATION AND PROPERTIES OF CERTAIN FLUORINE-CONTAINING ESTERS AND KETONES1 By B. T. McBee and E. R. W ilson^

1 . C o n ta in s m a t e r ia l from Mr. E . R. HELlson1s d o c to r a l t h e s i s . 2 . P r e s e n t A d d ress: P r o c te r and Gamble C o ., C in c in n a ti , O hio.

The a c e t o a c e t i c e s t e r c o n d e n s a tio n h a s b een th e s u b je c t o f many p a p e r s , b u t v e r y l i t t l e work h a s b een done i n t h e s tu d y o f th e e f f e c t o f f l u o r i n e i n th e co n d en sin g e s t e r s , o r o f th e e f f e c t o f f l u o r i n e on th e p r o p e r t i e s o f th e r e s u l t i n g y d - k e to e s t e r s .

A l i t e r a t u r e su rv e y r e v e a le d

no r e c o r d o f any a c e t o a c e t i c e s t e r c o n ta in in g more th a n th r e e h a lo g e n atom s, o r one i n w hieh b o th o f th e a lp h a a s w e ll a s one o r more o f th e gamma p o s i t i o n s w ere s u b s t i t u t e d by h a lo g e n s .

P re v io u s a tte m p ts to p r e ­

p a r e su ch compounds w ere u n s u c c e s s f u l . ^ ^

3 . Cope, J . Am. Chem. S o c ., 5>8, $70 (1 9 3 # ). U. Henne and Newman, i b i d . , 6 9 , 1819 (19U 7).

A rn d t, Loewe, and Capuano^ have found t h a t th e r e a c t i o n s o f

5» A rn d t, Loewe, and Capuano, Rev, f a c u l t é s c i . u n iv . I n s t ^ p h u l r 8A. 12 2$2 (1943) • [ C. A. , 39: I 62E J *

ii

compounds o f th e s t r u c t u r e R^CO-CR1R1 1-CO^R111 a r e g r e a t l y in f lu e n c e d by t h e n a tu r e o f R, R*, and R*1, and to a l e s s e r e x te n t by R*11 .

I f R is a

m ethyl g ro u p , f o r exam ple, th e s u b s t i t u t i o n o f hydrogen by h a lo g e n de­ c r e a s e s th e e l e c t r o n d e n s it y o f th e c a rb o n y l c a rb o n atom making i t r e l a ­ t i v e l y more p o s i t i v e .

T h is f a v o r s fo rm a tio n o f th e e n o l form o f th e

e s t e r and i n c r e a s e s th e te n d e n c y f o r th e fo rm a tio n o f h y d r a te s , a lc o h o la t e s , k e t a l s , and e n o l e t h e r s . c h lo ra l.

In t h i s re s p e c t i t i s v e ry s im ila r to

As e v id e n c e o f i t s s t a b i l i t y , th e h y d r a te o f m ethyl

t r i c h l o r o a c e t o a c e t a t e g iv e s a r e d c o lo r w ith f e r r i c c h lo r id e o n ly a f t e r s ta n d in g f o r some tim e , a lth o u g h p u re m eth y l Y ,Y ,Y - tr ic h lo r o a c e to a c e t a t e g iv e s an im m ediate d a rk re d c o l o r .

S im i la r l y , m eth y l Y ,> ,Y -

t r i c h l o r o a c e t o a c e t a t e i s d i f f i c u l t to p u r if y due t o th e g r e a t s t a b i l i t y o f t h e a l c o h o l a t e , and th e e q u ilib r iu m betw een e n o l, k e to n e , and a lc o h o la te .

I n ag reem en t w ith t h i s . D é s ira n t^ found t h a t e t h y l > , > - d i f l u o r o -

6 . D é s ir a n t, B u l l , s c i . a c a d . r o y . B e lg . ,

[V]» IS , 966-82 (192 9 )•

a c e t o a c e t a t e form s a s t a b l e h y d r a te ( n o t i s o l a t e d ) , and S w a rts? found

7 . S m a rts, i b i d . t [ $ ] , 1 2 , 679-721 ( 1926) .

t h a t e t h y l Y ,Y ,Y - t r i f l u o r o a c e t o a c e t a t e h a s a s tr o n g te n d e n c y to h y d r a t e . One d i f f i c u l t y i n th e i n v e s t i g a t i o n o f th e s e compounds i s th e f a c t t h a t th e h a lo g e n atoms a r e o f te n e a s i l y rem oved.

C o n se q u e n tly , i t

mas a n t i c i p a t e d t h a t a /& - k e to e s t e r c o n ta in in g f l u o r i n e i n th e a lp h a and gamma p o s i t i o n s w ould g iv e u n u s u a l r e a c t i o n s , s in c e u n l i k e o th e r

iii

h a lo g e n ato m s, t h e e a r b o n - f lu o r in e bond i s v e r y s t a b l e and m ig r a tio n o r rem oval o f th e f l u o r i n e atom i s d i f f i c u l t .

I n a d d iti o n , s in c e f l u o r i n e

i s th e m ost e l e c t r o n e g a t i v e o f t h e e le m e n ts , th e / 2 - c a rb o n atom s h o u ld be much more e l e c t r o p o s i t i v e th a n i n o r d i n a r y ^ - k e t o e s t e r s , le a d in g one t o e x p e c t u n u s u a l r e a c t i o n s o f th e k e to g ro u p .

The p u rp o se o f t h i s r e s e a r c h

th e n was t o p r e p a re su ch a compound and s tu d y i t s p r o p e r t i e s . P r e p a r a tio n o f E th y l c< ,ct,> ,y - T e t r a f l u o r o a c e t o a c e t a t e . ^ The m ost w id e ly u se d m ethod f o r t h e p r e p a r a tio n o f /&*-keto e s t e r s i s th e a c e t o a c e t i c e s t e r c o n d e n s a tio n .

The u s u a l b a s e eaqployed i s sodium

e th o x id e , b u t t h i s i s n o t a p p l i c a b le t o th e p r e p a r a t io n o f oC,ol,y/r— s u b s t i t u t e d / 3 - k e t o e s t e r s s in c e sodium e th o x id e i s to o weak a b a s e to f o r c e t h e e q u ilib r iu m r e a c t i o n s in v o lv e d u n le s s th e r e i s an e a s i l y remov­ a b le p r o to n i n th e f i n a l p r o d u c t. th a t in a re c e n t in v e s tig a tio n

C o n seq u en tly , i t i s n o t s u r p r i s i n g

H enne^

was u n a b le to cau se th e s e l f ­

c o n d e n s a tio n o f e t h y l d i f l u o r o a c e t a t e by means o f sodium e th o x id e . N e ith e r i s i t s u r p r i s i n g t h a t h e was u n a b le t o condense e th y l d i f l u o r o ­ a c e t a t e w ith o t h e r e s t e r s t o form th e

- d if lu o r o - y ^ - k e to e s t e r s ,

s in c e c o n tr a r y t o p o p u la r o p in io n t h a t th e , V t e t r a f l u o r o a c e t o a c e t a t e , and i n th e f a c t t h a t e th y l eu ,c i,> ,> - t e t r a f lu o r o a e e t o a c e t a t e c a n n o t b e d i s t i l l e d from th e r e a c t i o n m ix tu re u n t i l a f te r a c id ific a tio n . E th y l c,> - t e t r a f lu o r o ac e to a c e t a t e i s v e r y d i f f i c u l t to o b ta in p u re .

R e c t i f i c a t i o n i s accom panied by a r i s e i n te m p e ra tu re

fo llo w e d by a d ro p i n te m p e ra tu re below t h a t a t th e b e g in n in g o f th e re c tific a tio n .

E x a m in atio n o f th e r e f r a c t i v e in d e x o f th e v a r io u s

f r a c t i o n s shows t h a t t h e p ro d u c t i s n o t p u re a f t e r one r e c t i f i c a t i o n , a lth o u g h r e p e a te d r e c t i f i c a t i o n o f th e same f r a c t i o n s te n d s t o b r in g t h e r e f r a c t i v e in d e x i n t o c l o s e r a g reem en t.

From t h i s and t h e v a r io u s

p r o p e r t i e s o f t h e e s t e r , i t h a s b een co n clu d ed t h a t th e e s t e r a s p r e ­ p a r e d i s i n e q u ilib r iu m w ith v a r y in g q u a n t i t i e s o f th e a lc o h o la te o r h y d r a te .

T h is a g r e e s w ith t h e f a c t t h a t th e e s t e r r e a c t s w ith w a te r o r



a lc o h o l w ith l i b e r a t i o n o f h e a t -

A ttem p ts t o i s o l a t e th e h y d r a te o r

a lc o h o l a t e w ere u n s u c c e s s f u l D e r i v a t i v e s .— A s u rv e y o f th e l i t e r a t u r e d i s c l o s e d few c a s e s i n w hich th e u s u a l d e r i v a t i v e s f o r th e e s t e r o r k e to gro u p have been p r e p a re d f o r

-h a lo -/^ -k e to e s t e r s .

S im ila r l y , we w ere u n a b le t o p r e ­

p a r e any o f th e s e d e r i v a t i v e s f o r e th y l

ol ,ec,>, >

-te tr a f lu o ro a c e to —

a c e t a t e , a lth o u g h t h e 2, lt- d in itr o p h e n y lh y d ra z o n e , th e s e m ic a rb a z o n e , th e h y d ra zo n e , t h e N -b en zy lam id e, and th e amide o r im in e w ere a tte m p te d . W ith s e m ic a rb a z id e h y d r o c h lo r id e , h y d r a z in e , and ammonia, d e f i n i t e compounds a p p a r e n tly w ere form ed, b u t t h e i r s t r u c t u r e s have n o t been a s c e rta in e d . H y d r o ly s is »- When e t h y l £*,,>• - t e t r a f l u o r o a e e t o a c e t a t e was r e f lu x e d w ith 1056 s u l f u r i c a c i d , h y d r o ly s is was co m p lete w ith in a few h o u rs.

Of i n t e r e s t i s th e f a c t t h a t more th a n 100% o f e th a n o l was

i s o l a t e d from th e h y d r o ly s is o f th e c ru d e e s t e r , a n o th e r i n d i c a t i o n o f th e p re s e n c e o f a l c o h o l a t e .

The anhydrous a c id was o b ta in e d by rem oval

o f th e w a te r th ro u g h a z e o tr o p ic d i s t i l l a t i o n w ith b e n z e n e . r e a d i l y form s t h e s o l i d m o n o h y d rate.

The a c id

S i m i l a r l y to t h e e s t e r , th e

-

k e to a c id does n o t e a s i l y form t h e u s u a l d e r i v a t iv e s f o r th e k e to o r a c id g ro u p . C le a v a g e . - The a c c e p te d mechanism f o r th e c le a v a g e o f X ? -k e to a c id s in v o lv e s th e f o rm a tio n o f t h e e n o la te io n o f th e r e s u l t i n g k e to n e a s an i n t e r m e d i a t e .

However, a s m entioned p r e v io u s ly , t h e fo rm a tio n o f

th e d if lu o r o - c a r b a n io n i s d i f f i c u l t , and hence c le a v a g e w ould be e x p e c te d to be d i f f i c u l t .

C leav ag e was acco m p lish ed w ith t h e u s e o f c o n s t a n t - b o i l ­

in g h y d r o c h lo ric a c id , and 1 , 1 , 3, 3 - te tr a f l u o r o a c e t o n e was i s o l a t e d a s th e

h y d r a te .

The pure anhydrous k e to n e was prepared by treatment of the

hydrate with concentrated sulfuric acid, from which it distills in near­ ly pure form.

1,1,3,3-Tetrafluoroacetone reacts with water (or alcohol)

with all the vigor of acetyl chloride, and the resulting hydrate no longer gives the usual tests for a ketone. The b o i l i n g p o i n t o f 1 , 1 , 3 , 3 - te tr a f T u o r o a c e to n e i s w orthy o f n o te .

M o n o flu o ro aceto n e b o i l s a t 72° ( 7 8 ° )^ * " ^ ; 1 ,1 - d if lu o r o a c e to n e ,

9 . Ray, N a tu re , 132, 7h9 (1 9 3 3 ). 1 0 . D av ies and D ick , J . Chem. S o c . , I , U83 (1 9 3 2 ).

ii6 . 5° $ 1 , 1 , 1- t r i f l u o r o a c e t one, 2 1 . 9° ^ , and h e x a f iu o ro a c e to n e , - 28°

1 1 . P ukubara and B igelow , J . Am. Chem. S oc. , 6 3 , 788-91 (l9 U l)«

Thus one would n o t p r e d i c t f>7 «6° f o r th e b o i l i n g p o i n t o f 1 , 1 , 3 , 3 - t e t r a f lu o r o a c e to n e .

T h is u n u su a l b o i l i n g p o i n t i s i n d i c a t i v e o f th e s tr o n g

hydrogen b o nding in d u c e d by th e n e g a tiv e gro u p s o f th e m o le c u le . R e d u c tio n .

E th y l d j C i / y / y - t e t r a f l u o r o a c e t o a c e t a t e was s u c c e s s ­

f u l l y red u c e d w ith l i t h i u m aluminum h y d rid e t o g iv e 2, 2, L A - t e t r a f l u o r o 1 , 3 - b u ta n e d io l.

T h is g ly c o l i s an o d o r le s s , c l e a r , s ir u p y l i q u i d a t

room te m p e ra tu re s and form s a g l a s s upon c o o lin g i n D ry I c e .

I t is

e t h e r - s o l u b l e a s w e ll a s w a te r - s o lu b le , b u t s e p a r a t e s from c o ld b e n z e n e . Mixed C o n d e n s a tio n s .

U n s u c c e ss fu l a tte m p ts w ere made t o u s e

e t h y l d i f l u o r o a c e t a t e a s th e e n o liz in g e s t e r i n c o n d e n s a tio n s w ith a n o th e r e s t e r o r a c id c h lo r id e t o y i e l d an o c ,d - d if lu o r o - / # - k e to e s t e r .

v il

However# t h e r e a c t i o n w ith a c id c h l o r id e s d id y i e l d p r o d u c ts o f i n t e r e s t , s in c e th e y in v o lv e d a c y l a t i o n o f a h e m ik e ta l, a r e a c t i o n o f in f r e q u e n t o c c u r re n c e , and gave f u r t h e r i n s i g h t i n t o t h e a c t i v i t y o f th e k e to group i n e t h y l o c ^ t,> ,> - t e t r a f l u o r o a c e t o a c e t a t e • I n an a tte m p t t o p r e p a r e e th y l d if lu o r o m a lo n a te by c a rb é th o x y ­ l a t i o n o f e th y l d i f l u o r o a c e t a t e w ith e t h y l c h lo r o c a r b o n a te , a good y i e l d o f a h i g h - b o i l i n g l i q u i d was fo u n d .

The m o le c u la r w e ig h t, b o i l i n g p o i n t ,

and e le m e n ta l a n a l y s is o f t h e p r o d u c t, how ever, do n o t a g re e w ith t h a t o f e th y l d if lu o r o m a lo n a te . fo rm u la

.

I n s t e a d th e y a g re e c l o s e l y w ith th e e m p ir ic a l

The compound was b e li e v e d t o have one o f th e f o llo w ­

in g s t r u c t u r e s s o - c o - o c 2 H£

CHF2-C-CF2-CO-OC2H£

o c 2h 5

CHF2-C0-CF2-C -0-C 0-0C 2H£

Ôc 2 h 5

Ôc 2 h 5

I

II

A p ro b a b le mechanism c an b e g iv e n f o r th e f o rm a tio n o f e i t h e r compound (I) or ( I I ) .

T h is in v o lv e s f i r s t th e f o rm a tio n o f e t h y l ,>- t e t r a ­

f lu o r o a c e t o a c e t a t e th ro u g h th e s e lf - c o n d e n s a tio n o f e th y l d i f l u o r o a c e t a t e fo llo w e d by a d d i t i o n o f th e l i b e r a t e d e th o x id e i o n t o a c a rb o n y l group t o g iv e ( I I I ) o r ( IV ) . 0 CHFg-C-CFg-CO-OCgH^

0 CHFg—CO—CFg—C—OCgH^

OCgHf-

OCgHj,

in

iv

A c tu a lly , s t r u c t u r e s s i m i l a r t o ( t i l ) a r e th e p o s tu l a t e d i n te r m e d ia te s i n th e a c c e p te d mechanism f o r t h e a c e t o a c e t i c e s t e r c o n d e n s a tio n .

E ith e r

( I I I ) o r (IV ) c o u ld th e n r e a c t w ith e th y l c h lo r o c a rb o n a te t o g iv e r e s ­ p e c tiv e ly ( I ) o r ( I I ) .

To p ro v e th e r e a c t i o n c o u ld go th ro u g h th e

v iii

p o s t u l a t e d m echanism , e t h y l

- t e t r a f l u o r o a c e t o a c e t a t e was added

t o an e q u iv a le n t amount o f sodium e th o x id e i n e t h e r •

An e q u iv a le n t

amount o f e th y l c h lo r o c a rb o n a te was th e n added t o th e m ix tu re , and th e same compound, ( I ) o r ( I I ) , was i s o l a t e d by vacuum r e c t i f i c a t i o n .

I n an

a tte m p t t o d i s t i n g u i s h betw een ( I ) and ( I I ) , e t h y l t r i f l u o r o a c e t a t e was r e a c te d w ith sodium e th o x id e to g iv e t h e sodium s a l t o f th e h e m ia c e ta l. ühen t h i s s a l t was t r e a t e d w ith e t h y l c h lo r o c a r b o n a te , th e e q u ilib r iu m betw een sodium e th o x id e and th e s a l t o f th e h e m ia c e ta l was r e v e rs e d w ith t h e fo rm a tio n o f e t h y l c a r b o n a te and th e re c o v e ry o f e th y l t r i ­ f lu o r o a c e t a t e .

S in c e th e t r i f l u o r o - a c e t a l i s n o t s t a b l e u n d e r th e s e

c o n d itio n s , t h e d i f l u o r o - a c e t a l (HT) s h o u ld be even l e s s s t a b l e . One o t h e r s t r u c t u r e was c o n s id e re d i n th e i n v e s t i g a t i o n .

An

e x p e c te d p ro d u c t o f th e r e a c t i o n w ould be d i e t h y l 2, 2,U > U - te tr a f lu o r o 3- o x o - g l u t a r a t e a s shown by th e f o llo w in g s t e p s . 1.

c h f 2 - c o - c f 2 - c o - o c 2 H£



5 c 2H£ — »

c f 2 - co - c f 2 - c o - o c 2 H£

f

c 2 h ^ oh

2.

OFg-CO-CFg-CO-OCgH^ + Cl-CO-OCgH^ — » CgH^O-CO-CFg-CO-CFg-CO-OCgH^+Cl"

The e le m e n ta l a n a l y s i s d id n o t c o n firm t h i s compound, n o r d id i t seem l i k e ­ l y t h a t t h e e th o x id e io n c o u ld c a u s e rem oval o f th e 'V -h y d ro g en atom s in c e i t d id n o t remove th e

-h y d ro g e n o f e th y l d i f l u o r o a c e t a t e .

As p r o o f o f s t r u c t u r e , th e c o n d e n s a tio n p ro d u c t was red u ced w ith l i t h i u m aluminum h y d r id e .

The p r o d u c t o f th e r e d u c ti o n was 2 ,2 ,U ,U -

t e t r a f l u o r o - 1 , 3- b u ta n e d i o l, th e same g ly c o l o b ta in e d from th e s i m i l a r r e d u c tio n o f e th y l e L ^ ,-y ,> - t e t r a f l u o r o a c e t o a c e t a t e .

T h is g ly c o l c o u ld

n o t have b een d e r iv e d from d i e t h y l 2, 2,li, L - t e t r a f l u o r o - 3- o x o - g l u t a r a t e b u t w ould be th e e x p e c te d p ro d u c t from th e r e d u c tio n o f e t h y l 1- c a r b e th o x y 2 - e t h o x y - l ,1 , 3 , 3 - t e t r a f l u o r o - 2 -p ro p y l c a r b o n a te ( I ) .

The above e v id e n c e .

ix

■ together n i t h t h e p r e v io u s ly d e m o n stra te d a c t i v i t y o f t h i s k e to g ro u p > i n d i c a t e d c o n c lu s iv e ly t h a t th e c o r r e c t s t r u c t u r e i s ( ! ) • I n a s i m i l a r r e a c t i o n , b e n z o y l c h l o r id e was s u b s t i t u t e d f o r e t h y l c h lo r o c a rb o n a te and th e c o rre s p o n d in g a c y la te d h e m ik e ta l, 1c a r b e th o x y -2- e t h o x y - l , 1 ,

3- t e t r a f l u o r o - 2- p ro p y l b e n z o a te was fo rm ed .

E x p e rim e n ta l P r e p a r a tio n o f E th y l

-T e tra flu o ro a c e to a c e ta te . - A

500- m l . , 3-n e ck e d f l a s k was eq u ip p ed w ith a s e a le d s t i r r e r , d ro p p in g f u n n e l, and a r e f l u x c o n d e n se r s to p p e r e d by a c a lc iu m c h lo r id e d ry in g tu b e , and a rra n g e m e n ts w ere made t o m easure ev o lv ed h y d ro g en .

The

system was flam ed d ry , and 1 0 .3 8 g . (0.U 3 m ole) o f sodium h y d r id e , 158 g . (1 .2 7 m o les) o f e th y l d i f l u o r o a c e t a t e , and e i g h t g la s s m arb le s were added; a f t e r w hich th e a i r was r e p la c e d by d ry n it r o g e n .

The

s t i r r e d s o l u t i o n was r e f lu x e d f o r one and o n e - h a lf h o u rs d u rin g w hich tim e 9*7 l i t e r s (100%) o f h ydrogen was e v o lv e d .

The s o lu t i o n was

c o o le d q u ic k ly and p o u re d i n t o a b e a k e r c o n ta in in g 200 g . o f c ru sh e d i c e and 20 g . o f g l a c i a l a c e t i c a c i d .

The m ix tu re was th o ro u g h ly shaken

w ith 200 m l. o f e t h e r , a f t e r w hich th e aqueous l a y e r was s e p a r a te d and e x t r a c t e d w ith f o u r a d d i t i o n a l p o r ti o n s o f d im in is h in g q u a n t i t i e s o f e th e r.

The com bined e t h e r e x t r a c t s w ere d r ie d w ith sodium s u l f a t e

fo llo w e d by D r i e r i t e .

Vacuum d i s t i l l a t i o n , fo llo w e d by vacuum r e c t i f i ­

c a t i o n gave 61;.9 g* o f e th y l e t , « ,> ,> - t e t r a f l u o r o a c e t o a c e t a t e , b .p . 39-32° (3 mm.), n ^ l .3 5 U 2 , and 17 g . o f re c o v e re d e th y l d i f l u o r o a c e t a t e . T h is i s a y i e l d o f 7l|% b ase d on sodium h y d r id e , 5 6 . b a s e d on e th y l d i ­ f lu o r o a c e t a t e .

X

A n a l. C a lc d . f o r C6H6FU°38 ^ Found:

^ e6^ 5 H> 2e" >

F» 3 7 -6 0 .

C, 3 5 -6 ; H, 2 . 9 8 ; F, 3 7 -9 P r e p a r a tio n o f

- T e t r a f l u o r o a c e t o a c e t i c A c id .- S e v e n ty -

two grains (O .l^l m ole) o f e t h y l ac, « , > , > - t e t r a f l u o r o a c e t o a c e t a t e was r e ­ f lu x e d w ith 5>0 m l. o f 10% s u l f u r i c a c i d .

A rrangem ents w ere made f o r th e

rem oval o f th e l i b e r a t e d e th a n o l, and a t o t a l o f 1 8 .2 g . ( 106%) o f 95>% e th a n o l was c o l l e c t e d i n two h o u r s .

The et,Qti,> ,> - t e t r a f l u o r o a c e t o a c e t i c

a c id was i s o l a t e d from th e aqueous s o lu t i o n by c o n tin u o u s e x t r a c t i o n w ith e t h e r and d r ie d w ith sodium s u l f a t e , fo llo w e d by D r i e r i t e , and f i n a l l y azeo t r o p i c d i s t i l l a t i o n w ith b e n z e n e .

Vacuum d i s t i l l a t i o n gave 28. U g .

(ii6%) o f a c l e a r l i q u i d , b . p . 72° (2 mm.), w hich s o l i d i f i e d a t room te m p e ra tu re t o e x tre m e ly h y g ro sc o p ic c r y s t a l s .

A n e u t r a l e q u iv a le n t

ta k e n on t h e f r e s h l y d i s t i l l e d a c id a g re e d w ith t h e c a l c u l a t e d v a lu e f o r anhydrous «Cyct,>, > - t e t r a f l u o r o a c e t o a c e t i c a c id . th e m o nohydrate, m .p .

14.3 - 5 ° >

w h ic h

The a c id r e a d i l y form s

can be r e c i y s t a l l i z e d from a b e n z e n e -

e th e r s o lu tio n . A n a l. C a lc d . f o r e q u i v ., 17U -0, 17U -3.

n e u t . e q u i v ., 17U -06.

Found: n e u t.

C a lc d . f o r C, H, F, 0. : C, 2 5 -0 0 ; H, 2 .0 8 . 4 4 4 4

Found:

C, 2 5 -0 1 ; H, 2 .0 8 . P r e p a r a tio n o f 1 ,1 ,3 * 3 - T e tr a f lu o r o a c e to n e - - T h i r ty grams (0 .1 5 m ole) o f e t h y l e t

- t e t r a f l u o r o a c e t o a c e t a t e was r e f lu x e d w ith

50 m l. o f c o n s t a n t - b o i l i n g h y d r o c h lo ric a c id f o r f o r t y - e i g h t h o u r s .

The

aqueous s o l u t i o n i n th e f l a s k was th e n e x t r a c te d c o n tin u o u s ly w ith e th e r f o r t h i r t y - s i x h o u rs , a f t e r w hich th e e t h e r e x t r a c t was d r ie d by sodium s u l f a t e fo llo w e d by D r i e r i t e .

The e t h e r was removed on a w a te r b a t h , and

th e r e s i d u e was r e c t i f i e d th ro u g h a 1 2 -in c h V ig reau x column t o g iv e 10 g .

xi

( 6 1 . 3%) o f 1 , 1 , 3, 3- t e t r a f l u o r o a c e t o n e m onohydrate, b . p . U6-7° (25 mm.), id iic h s o l i d i f i e d on c o o lin g .

The h y d r a te su b lim es a t room te m p e r a tu re ,

and may be p u r i f i e d i n t h a t m anner, m .p . U5 * D i s t i l l a t i o n o f 5 m l. o f th e h y d r a te from c o n c e n tr a te d s u l f u r i c a c id fo llo w e d by r e c t i f i c a t i o n o f th e d i s t i l l a t e gave h g- o f 1 , 1 , 3 >3- t e t r a f l u o r o a c e t o n e , b . p . 5 7 *6° , 20

nÿ 1 .3 0 2 5 . A n a l. C a lc d . f o r C ^ H ^ O g : C, 2U.3U; H, 2 .7 0 . H, 2 .6 9 .

C a lc d . f o r C ^ F ^ O : C, 2 7 .7 1 ; H, 1.51*.

Found: C, 21*.12$

Found: C, 2 7 .5 8 ;

H, 1 .5 7 . P r e p a r a t i o n o f 2,2,1*» U - T e tr a f lu o r o - 1 , 3- b u ta n e d i o l . f i v e grams ( 0 . 121* m ole) o f e t h y l

Tw enty-

t t ,e i ,> ,> - t e t r a f l u o r o a c e t o a c e t a t e

d is s o lv e d i n 50 m l. o f anhydrous e t h e r was re d u c e d w ith 6 .5 8 g . ( 0 .2 m ole) o f l i t h i u m aluminum h y d rid e i n 150 m l. o f i c e - c o l d anhydrous e t h e r f o llo w in g th e m ethod o f Nystrom and Brown.

1P

H y d ro ly sis o f th e com plex was

1 2 . Nystrom and Brown, J . Am. Chem. S oc. , 6 9 , 1197 (191*7).

acco m p lish ed w ith 21*6 g . o f 20^ s u l f u r i c a c i d .

The p r o d u c t was i s o l a t e d

by c o n tin u o u s e x t r a c t i o n w ith e t h e r and d r ie d w ith sodium s u l f a t e fo llo w e d by a z e o tr o p ic d i s t i l l a t i o n w ith ben zen e u n t i l th e te m p e ra tu re re a c h e d 8 0 °.

On c o o lin g t h e p o t r e s id u e , th e anhydrous g ly c o l s e p a r a te d

from th e s o l u t i o n and was f u r t h e r p u r i f i e d b y d i s t i l l a t i o n th ro u g h a 12in c h V ig reau x column t o g iv e 1 0 .2 g . (50.7% ) o f 2 ,2 ,1 * ,l * - t e t r a f l u o r o - l , 3 b u ta n e d ie l, b . p . 80- 1° (2 mm.), n ^ l . 3800. A n al. C a lc d . f o r C ^ F ^ O g : C, 29.61*; H, 3 .7 3 .

Found: C, 2 9 .6 ;

H, 3 -7 2 . The p - n itr o b e n z o a te was p r e p a re d b y s ta n d a r d m ethods, m .p. 95 °•

x ii

I n r e c r y s t a l l i z a t i o n s from e th a n o l, th e e s t e r s e p a r a te s a s an o i l u n le s s d i l u t e s o l u t i o n s a r e a llo w e d t o c r y s t a l l i z e s lo w ly . A n a l. C a lc d . f o r c1 8Hi 2 FliN20 8 ! N> 6e08e

Found: N> 6 «1 0 »

P r e p a r a tio n o f E th y l l - C a r b e t h o x y - 2 - e t h o x y - l ,1 ,3 ,3 - t e t r a f l u o r o 2- p r o p y l C a rb o n a te . -

The equipm ent u se d was th e same a s t h a t u s e d i n th e

p r e p a r a t i o n o f e t h y l e t,e c ,> ,> - t e t r a f l u o r o a c e t o a c e t a t e .

Anhydrous d io x an e

(300 g . ) was d i s t i l l e d from sodium h y d rid e i n t o th e f l a s k , and 12 g . ( 0 .5 m ole) o f f in e ly - g r o u n d sodium h y d rid e ( d ry -b o x ) was ad d ed .

The

s t i r r e d s o l u t i o n was h e a te d t o r e f l u x te m p e r a tu re , and 62 g . ( 0 .5 m ole) o f e t h y l d i f l u o r o a c e t a t e was p la c e d i n th e f u n n e l, w ith a b o u t o n e - h a lf o f t h e e s t e r b e in g added t o th e s o lu t i o n a t o n c e .

The r e a c t i o n was

i n i t i a t e d b y th e a d d i t i o n o f 2 m l. o f e th a n o l, and a f t e r a f i f t e e n min­ u t e in d u c t i o n p e r io d , e v o lu tio n o f hydrogen became r a p i d .

The re m a in d e r

o f th e e s t e r was ad d ed slo w ly , and when th e e v o lu tio n o f hydrogen slow ed ( f o r t y - f i v e m in u te s ) , 108*6 g . ( l m ole) o f e t h y l c h lo r o c a rb o n a te was added a t a r a t e m a in ta in in g r e f l u x .

Hydrogen c e a s e d t o e v o lv e i n one

h o u r, a t o t a l o f 8 l i t e r s b e in g c o l l e c t e d .

The s o lu t i o n was r e f lu x e d

f o r an a d d i t i o n a l s i x h o u r s , th e n c o o le d , vacuum f i l t e r e d , and vacuum d is tille d .

R e c t i f i c a t i o n o f th e d i s t i l l a t e gave 35 g • o f a c o l o r l e s s

l i q u i d , b . p . 9 8 .5 ° (1 mm.), n ^ l.3 9 U 3 *

T h is i s a c o n v e rs io n o f Uh-h%

b a se d on e t h y l d i f l u o r o a c e t a t e . A n a l. C a lc d . f o r C ^ H ^ F ^ O ^ : C, i|1 .2 5 ; H, 5*0U; m ol. w t . , 320. Founds C, k l . l i ; H, 5 .1 6 ; m ol. w t ., 300. I n a n o th e r e x p e rim e n t 62 g . ( 0 .5 m ole) o f e th y l d i f l u o r o ­ a c e t a t e , 6 g . ( 0 .2 5 m ole) o f sodium h y d r id e , and 5U g* ( 0 .5 m ole) o f e th y l c h lo r o c a rb o n a te w ere condensed w ith o u t any s o lv e n t , and s u f f i c i e n t

xii l

tim e was a llo w e d f o r t h e p rim a ry s e lf - c o n d e n s a tio n o f e t h y l d i f l u o r o ­ a c e t a t e t o go t o c o m p le tio n b e f o r e th e e th y l c h lo r o c a rb o n a te was added. By t h i s method t h e y i e l d was i n c r e a s e d t o 60%. P r e p a r a tio n o f l- C a r b e th o x y - 2 - e th o x y - l>l , 3 » 3 - t e t r a f l u o r o - 2 p r o p y l B e n z o a te . -

T h is r e a c t i o n was c a r r i e d o u t i n th e same m anner as

th e p r e c e d in g e x p e rim e n t.

I n th e f l a s k w ere p la c e d 2 0 1 .5 g- o f anhydrous

d io x a n e , 2U»8 g . ( 0 .2 m ole) o f e t h y l d i f l u o r o a c e t a t e , and U.3 g . ( 0 .2 m ole) o f sodium h y d r id e .

The s o lu t i o n was b ro u g h t t o r e f l u x , and a f t e r

e v o lu tio n o f 2 l i t e r s o f h y d ro g en , 5 6 .2 g . ( 0 .I4. m ole) o f b e n z o y l c h lo r id e was d ro p p ed slo w ly i n t o th e s o l u t i o n .

E v o lu tio n o f hydrogen c e a se d when

a b o u t o n e - h a lf o f th e b e n z o y l c h l o r id e was added, and th e re m a in d e r was added q u ic k ly .

The s o l u t i o n was allo w ed to s ta n d f o r two h o u r s , vacuum

f i l t e r e d , and r e c t i f i e d u n d e r vacuum to 6U° (5 a m .) .

The s o l i d p o t

r e s id u e was vacuum d i s t i l l e d t o g iv e a tw o -p h ase d i s t i l l a t e which was th e n d is s o lv e d i n e t h e r and w ashed w ith 10% sodium c a rb o n a te u n t i l no more ca rb o n d io x id e was e v o lv e d .

Vacuum r e c t i f i c a t i o n o f t h e d r ie d e t h e r

s o l u t i o n gave 5 g* o f a c o l o r l e s s l i q u i d , b . p . 126° (1 mm.), n ^ l . l i 5 9 2 . A n a l. C a lc d . f o r C ^ H ^ F ^ O ^ : C, 5 1 .Ill ; H, I4..5 8 * Found: C, 51.1*05 H, W 6 . R e d u c tio n o f E th y l l- C a r b e th o x y - 2 - e th o x y - l, 1 , 3 , 3 - t e t r a f l u o r o 2—p ro p y l C a rb o n a te . -

The te c h n iq u e u s e d i n t h i s r e d u c tio n was th e same

a s t h a t u s e d i n th e r e d u c t i o n o f e th y l

-te tr a f lu o ro a c e to a c e ta te .

F o rty -o n e grams (0 .1 3 mole) o f e t h y l l - c a r b e t h o x y - 2 - e th o x y - l ,1 , 3 > 3 - t e t r a ­ f lu o r o - 2- p ro p y l c a rb o n a te was re d u c e d w ith 1 3 .5 g . ( 0 .3 5 5 m ole) o f l i t h i u m aluminum h y d rid e t o g iv e 1 3 . U g . ( 66%) o f 2, 2, U ,U - t e t r a f l u o r o 1 , 3- b u t a n e d i o l .

I d e n t i f i c a t i o n o f t h i s compound was made th ro u g h th e

b o i l i n g p o i n t , 85° (5 mm.), t h e in d e x o f r e f r a c t i o n , n ^ l . 380$, and p r e ­ p a r a t i o n o f th e p - n itr o b e n z o a te , m .p . 95°• Acknowledgem ent. -

The a u th o r s w ish t o e x p re ss s in c e r e a p p re ­

c i a t i o n t o F i r e s t o n e T ir e and Rubber Company and A lli e d C hem ical and Dye C o rp o ra tio n f o r t h e f i n a n c i a l a s s i s ta n c e g iv e n i n t h i s i n v e s t i g a t i o n . We a l s o w ish t o e x p r e s s a p p r e c i a tio n t o E. I . du P ont de Nemours & Company f o r th e d o n a tio n o f t h e sodium h y d rid e u s e d i n th e s e e x p e rim e n ts

1.

The s e lf - c o n d e n s a tio n o f e th y l d i f l u o r o a c e t a t e h a s been

s u c c e s s f u l l y c a r r i e d o u t b y u s e o f sodium h y d r id e . «


t e t r a f l u o r o a c e t o a c e t i c a c id and th e h y d r a te and c le a v e d to g iv e 1 , 1 , 3 , 3t e t r a f l u o r o a c e t o n e and th e h y d r a te .

A ll o f th e s e compounds d is p la y

u n u s u a l p r o p e r t i e s due t o th e s tr o n g ly n e g a tiv e f l u o r i n e - c o n t a i n i n g gro u p s a d ja c e n t t o th e c a rb o n y l g ro u p . 2.

E th y l oc,« (,> ,> - t e t r a f l u o r o a c e t o a c e t a t e h a s b een c o n v e rte d

t o 2, 2 ,U ,U - t e t r a f l u o r o - 1 , 3- b u ta n e d io l, e th y l l - c a r b e th o x y - 2- e th o x y 1 *1 >3 , 3- t e t r a f l u o r o - 2- p r o p y l c a r b o n a te , and l- c a r b e th o x y - 2- e th o x y 1 , 1 , 3 , 3- t e t r a f l u o r o - 2- p r o p y l b e n z o a te .

XV

AN ABSTRACT D ep artm en t o f C h em istry and Purdue R esearch F o u n d atio n P urdue U n iv e r s ity , L a f a y e t te , I n d ia n a

ATTEMPTED PREPARATION OF DIELUOROKETBNE1 By B. T. McBee and E. R. TflB-lson^

1 . C o n ta in s m a t e r i a l from Mr. E. R. W ilso n ’ s d o c to r a l t h e s i s . 2 . P r e s e n t A d d ress:

P r o c te r and Gamble C o ., C in c in n a ti, O hio.

K eten e s a r e among t h e m ost v e r s a t i l e compounds o f o r g a n ic c h e m is tr y .

Not o n ly a r e th e y c a p a b le o f g iv in g m ost o f th e r e a c t i o n s

o f a c i d h a l i d e s and a n h y d rid e s , b u t i n a d d i tio n th e y undergo many a d d i­ tio n re a c tio n s .

The d im ers o f k e te n e s a r e a lm o st e q u a lly r e a c t i v e , t h e i r

u s e i n t h e p r e p a r a t i o n o f / 9 - k e t o compounds b e in g w e ll known.

Thus i t

was b e lie v e d t h a t th e p r e p a r a t i o n o f d if lu o r o k e te n e w ould g iv e o rg a n ic c h e m is tr y a v e r y v a lu a b le in te r m e d ia te f o r s y n th e tic work i n f l u o r i n e c h e m is tr y .

The p u rp o se o f t h i s i n v e s t i g a t i o n was to p r e p a r e d i f l u o r o ­

k e te n e and t o s tu d y i t s p r o p e r t i e s . E very r e a c t i o n deemed f e a s i b l e f o r t h e p r e p a r a tio n o f d i f l u o r o ­ k e te n e was a tte m p te d .

I n g e n e r a l, th e s e r e a c t i o n s may be d iv id e d i n t o

two g ro u p s; th o s e i n w hich an i n te r m e d ia te compound was r e a c t e d w ith some o t h e r c h em ic al t o p ro d u ce th e d e s ir e d d if lu o r o k e te n e , and th o s e i n w hich p y r o l y s i s o f some i n t e r m e d ia te compound b re a k s i t i n t o d i f l u o r o ­ k e te n e and o t h e r p r o d u c ts .

I n none o f th e s e r e a c t i o n s was any t r a c e o f

xvi

d if lu o r o k e te n e d e t e c t e d , a lth o u g h th e lo w - m o le c u la r- e e ig h t polym er may have b een p r e p a r e d . As a r u l e , no a tte m p t was made t o i s o l a t e d if lu o r o k e te n e a s such.

I n s t e a d , arra n g e m e n ts w ere made t o d e t e c t th e d if lu o r o k e te n e a s

d ifiu o ro a c e ta n ilid e .

The m ethod u s e d was fo u n d c a p a b le o f d e t e c t i n g l e s s

th a n th e e q u iv a le n t o f 0 .6 g . o f d i f l u o r o k e t e n e .

I n a l l e x p e rim e n ts ,

t h i s w ould r e p r e s e n t a n e g l i g i b l e y i e l d , and th u s th e ab sen ce o f d i f lu o r o a c e t a n i l i d e was ta k e n t o mean t h a t no d if lu o r o k e te n e was p ro d u ced i n th e r e a c t i o n . I n th e v a r io u s r e a c t i o n s s e v e r a l new compounds have b een p r e ­ p a re d i n t h e p r o c e s s o f making n e c e s s a r y in te r m e d ia te s o r a s b y - p ro d u c ts o f th e in v e s tig a te d r e a c tio n s .

No a n a ly s e s w ere made s in c e i n m ost c a s e s

th e i d e n t i f y o f t h e compound i s r a t h e r o b v io u s . R e a c tio n o f C h lo r o d if lu o r o a c e ty l C h lo rid e w ith Z in c . -

P o s s ib ly

th e o l d e s t g e n e r a l m ethod f o r th e p r e p a r a t io n o f k e te n e s i s th ro u g h th e d e h a lo g e n a tio n o f

- h a lo a c y l h a l i d e s b y z i n c . ^

W hile n o t g e n e r a lly

3 . S ta u d in g e r, B e r ., 38, 1735 (1 905)•

a p p lic a b le to

o( - c h lo r o a ç y l c h l o r id e s , a few n e g a tiv e ly s u b s t i t u t e d

k e te n e s have been p r e p a re d by t h i s m ethod, and th u s i t seemed a p p lic a b le f o r th e p r e p a r a t i o n o f d if lu o r o k e te n e .

T hree a tte m p ts w ere made t o d e -

h a lo g e n a te c h l o r o d if l u o r o a c e t y l c h lo r id e w ith z in c .

The a p p a r a tu s was

a rra n g e d so t h a t any d if lu o r o k e te n e form ed would d i s t i l l from th e s o lu ­ t i o n i n t o a b e n z e n e - a n ilin e t r a p and be d e te c te d a s d i f i u o r o a c e t a n i l i d e . T ra c e s o f h y d ro q u in o n e and a h i g h - d i l u t i o n te c h n iq u e w ere u se d t o

p r e v e n t p o ly m e r iz a tio n , b u t i n s p i t e o f t h i s , t h e o n ly r e a c t i o n p ro d u c t i s o l a t e d was a lo w ^-m o lecu lar-w eight polym er t h a t c o u ld n o t b e i d e n t i f i e d . D e h y d ro h a lo g e n a tio n o f D if lu o r o a c e ty l C h lo r id e .-

The d e h y d ro -

h a lo g é n a tio n o f a c y l h a l i d e s by t e r t i a r y am ines i s an e x c e l l e n t m ethod o f p r e p a r in g k e te n e s p ro v id in g th e y do n o t d im e riz e e a s i l y A l t h o u g h th e r e

U* S ta u d in g e r, i b i d . , 1*0, 111*8 (1907) •

i s no r e c o r d o f a r e a c t i v e k e te n e monomer b e in g p r e p a re d i n t h i s m anner, i t was b e lie v e d th e ap p ro ach m ig h t be f e a s i b l e w here th e k e te n e i s a g a s . To t e s t t h i s th e o r y , t r i a l r u n s w ere made w ith a c e t y l c h lo r id e and t r i e th y la m in e .

As e x p e c te d , th e r e a c t i o n was s u c c e s s f u l, k e te n e , d ik e te n e ,

and dehy d r a c e t i c a c i d a l l b e in g i s o l a t e d a s d e r i v a t i v e s .

T h is i s b e lie v e d

t o b e th e f i r s t p r e p a r a t i o n o f k e te n e , o r d ik e te n e by t h i s m ethod.

When

th e r e a c t i o n was a tte m p te d w ith d i f l u o r o a c e t y l c h l o r i d e , how ever, none o f th e d e s ir e d p r o d u c t, d if lu o r o k e te n e , was fo u n d .

I n s te a d , a lo w -m o le c u la r-

w e ig h t p o ly m er, su p p o se d ly t h a t o f d if lu o r o k e te n e , was form ed i n good y ie ld s .

No a tte m p t was made t o p o s i t i v e l y i d e n t i f y th e p o ly m er, s in c e

i t was u s e d im m e d ia te ly i n th e fo llo w in g r e a c t i o n . P y r o ly s is o f D iflu o r o k e te n e P olym er.

One o f th e b e s t m ethods

f o r th e p r e p a r a t i o n o f p u re k e te n e s i s th e p y r o ly s is o f th e d im er o f t h a t k e te n e .^

C o n se q u e n tly , th e polym er p re p a re d i n th e p re c e d in g e x p e rim e n t

$• B oese, I n d . Eng. Chem., 3 2 , 16 (191*0) •

was p y ro ly z e d i n an a tte m p t to p r e p a r e d i f l u o r o k e te n e .

A m o d if ic a tio n

o f t h e u s u a l k e te n e lamp was u s e d , and a rran g em en ts w ere made to i d e n t i f y

x v iii

any d i f lu o r o k e te n e form ed a s d i f i u o r o a c e t a n i l i d e .

No t r a c e o f d i f i u o r o ­

a c e t a n i l i d e c o u ld be fo u n d , th e o n ly i s o l a t e d compound b e in g th e a n i l i n e s i l i c o n t e t r a f l u o r i d e com plex. P r e p a r a t i o n and P y r o ly s is o f D i f lu o r o a c e ty lp h th a lim id e . -

D i­

m eth y l k e te n e h as b een p r e p a re d i n good y i e l d s th ro u g h t h e p y r o ly s i s o f i s o b u t y r l p h t h a l i m i d e S i n c e t h i s r e a c t i o n seemed a p p l i c a b l e , d i f l u o r o -

6 . Hurd and D u ll, J . Am. Chem. S o c. ,

21*32 (1 9 3 2 ).

a c e ty lp h th a lim id e ( a new compound) was p r e p a re d and p y ro ly z e d i n th e a tte m p t t o p r e p a r e d i f l u o r o k e t e n e .

The p r e p a r a tio n o f d i f l u o r o a c e t y l ­

p h th a lim id e was fo u n d t o be q u i t e d i f f i c u l t due t o t h e te c h n i c a l d i f f i ­ c u l t i e s in v o lv e d .

The fo rm a tio n from d i f l u o r o a c e t y l c h lo r id e and

p o ta ss iu m p h th a lim id e a p p a r e n tly p ro c e e d s i n n e a r ly q u a n t i t a t i v e y i e l d s , b u t g r e a t d i f f i c u l t y was e x p e rie n c e d i n s e p a r a tin g t h e d i f l u o r o a c e t y l ­ p h th a lim id e from th e p o ta ss iu m c h lo r id e form ed, th e u n r e a c te d p o ta ssiu m p h th a lim id e , and p h th a lim id e from th e h y d r o ly s is o f th e p r o d u c t, s in c e a l l o f th e s e m a t e r ia ls a r e r a t h e r i n s o l u b l e i n m ost o r g a n ic s o l v e n t s . I n a d d i t i o n , i t was fo u n d t h a t a b s o lu t e l y anhydrous c o n d itio n s m ust be o b se rv e d i n o r d e r t o p r e v e n t co m plete h y d r o ly s is o f th e d i f l u o r o a c e t y l ­ p h th a lim id e t o d i f l u o r o a c e t i c a c i d and p h th a lim id e .

Even u n d e r a p p a r e n t­

l y an h y d ro u s c o n d i t i o n s , th e d ec o m p o sitio n g r a d u a lly ta k e s p l a c e . ^ When im pure sam ples o f d if lu o r o a c e ty lp h th a lim id e w ere p y ro ly z e d , e x te n s iv e d e c o m p o sitio n to o k p l a c e , b u t th e p y r o ly s i s o f p u re d i f l u o r o ­ a c e ty lp h th a lim id e gave a good y i e l d o f a lo w - b o ilin g compound b e lie v e d t o be d i f l u o r o a c e t y l f l u o r i d e , a new compound.

A s u g g e s te d mechanism f o r

x ix

t h e r e a c t i o n in v o lv e s p a r t i a l d e c o m p o sitio n t o hyd ro g en f l u o r i d e w hich th e n c le a v e s th e d i f l u o r o a c e t y l p h th a lim id e t o d i f l u o r o a c e t y l f l u o r i d e and p h th a lim id e .

A n o th er b u t l e s s l i k e l y s u p p o s itio n i s t h a t d i f l u o r o ­

k e te n e i s form ed b u t th e n adds t o th e hyd ro g en f l u o r i d e w hich i s p ro d u ced i n v a r io u s d e c o m p o s itio n p r o c e s s e s t o g iv e d i f l u o r o a c e t y l f l u o r i d e . P r e p a r a t i o n and P y r o ly s is o f 1 , 1 - D if lu o r o a c e to n e .-

The b e s t 7 la b o r a t o r y p r e p a r a t i o n o f k e te n e i s th ro u g h th e p y r o ly s is o f a c e to n e .

7- W illiam s and H urd, J . O rg. Chem. , J?, 122 ( 191*0) •

C o n se q u e n tly , i t was b e lie v e d t h a t d if lu o r o k e te n e m ig h t be p r e p a r e d th ro u g h th e p y r o l y s i s o f 1 , 1 - d i f l u o r o a c e t o n e . 1 ,1 - D iflu o r o a c e to n e h as 0 b een p r e p a re d p r e v io u s ly , b u t a r a t h e r la b o r io u s m ethod was u s e d . We

8 . D é s i r a n t , B u l l , s c i . a c a d . r o y . B e lg .,

l £ , 966-82 (1929) •

have s h o rte n e d t h e tim e o f p r e p a r a ti o n and im proved th e y i e l d by c a r r y in g o u t th e h y d r o ly s is d i r e c t l y on th e c ru d e e n o l s a l t i n s t e a d o f i s o l a t i n g th e i n te r m e d ia te e th y l th e k e to n e ,

> , y - d i f l u o r o a c e t o a c e t a t e and th e n c le a v in g i t to

^ r r o l y s i s o f 1 , 1- d if lu o r o a c e to n e was u n s u c c e s s f u l, how ever,

com p lete d ec o m p o sitio n ta k i n g p l a c e . P y r o ly s is o f D if lu o r o a c e tic A c id . o f k e te n e i s th e p y r o l y s i s o f a c e t i c a c id .

A com m ercial p r e p a r a t i o n A c c o rd in g ly , th e p y r o ly s i s

o f d i f l u o r o a c e t i c a c id was a tte m p te d w ith th e a n t i c i p a t i o n o f fo rm in g d iflu o ro k e te n e . b e in g g iv e n o f f .

The p y r o ly s i s p ro c e e d s q u i t e r a p i d ly , d en se w h ite fumes When p a sse d i n t o an e t h e r - a n i l i n e s o l u t i o n , th e s e

XX

fum es c a u se an im m ed iate fo rm a tio n o f a w h ite g e la tin o u s p r e c i p i t a t e # However, no t r a c e o f d i f i u o r o a c e t a n i l i d e c o u ld b e fo u n d .

The p r e c i p i ­

t a t e was a n a ly z e d , and th e s o lu b le f l u o r i d e io n c o n te n t was found t o be such t h a t a q u a n t i t a t i v e y i e l d o f hydrogen f l u o r i d e was i n d i c a t e d .

From

t h i s i t h a s b e e n co n clu d e d t h a t p y r o ly s is o f d i f lu o r o a c e t i c a c id a t te m p e r a tu re s n e a r 300° le a d s t o com plete r u p tu r e o f t h e c a r b o n - f lu o r in e b o n d s.

E x p e rim e n ta l D e h a lo g e n a tio n o f C h lo r o d if lu o r o a c e ty l C h lo r id e .-

 ^00- m l. ,

3-n e c k e d f l a s k was f i t t e d w ith a s e a le d s t i r r e r , a m o d ifie d w a te r -c o o le d H ersh b e rg d ro p p in g fu n n e l mounted o v e r a s h o r t c o n d e n s e r, and a r e f l u x c o n d e n s e r.

Any uncondensed g a se s w ere l e d th ro u g h an i c e - c o l d e t h e r -

a n ilin e s o lu tio n to a liq u id a i r tr a p .

The f l a s k was c h arg ed w ith 20 g#

o f z in c , 30 g . o f e t h y l a c e t a t e , and 2 g . o f h y d ro q u in o n e .

A s o lu t i o n

o f 20 g . o f c h l o r o d if l u o r o a c e t y l c h lo r id e (p re p a re d i n 60% y i e l d b y th e m ethod o f Brown^) and 20 g . o f e th y l a c e t a t e was added t o th e f l a s k o v e r

9» Brown, J . Am# Chem. S o c ., 6 0 » 1325-8 (1 9 3 8 ).

a tw e n ty -tw o h o u r p e r io d .

At th e end o f t h i s tim e , th e e t h e r - a n i l i n e

s o l u t i o n was d i s t i l l e d to 200°^ le a v in g a s o l i d r e s i d u e .

T h is r e s i d u e

was r e c r y s t a l l i z e d from h o t 10% h y d r o c h lo r ic a c id t o g iv e c r y s t a l s o f c h l o r o d i f l u o r o a c e t a n i l i d e , m .p. 68° .

These w ere i d e n t i f i e d by com pari­

son th ro u g h a m ixed m e ltin g p o in t w ith unam biguously p re p a re d c h l o r o d if l u o r o a c e t a n i l i d e , m .p. 68° .

The s o l u t i o n i n th e r e a c t i o n f l a s k was

xxi

f i l t e r e d , and th e s o lv e n t d i s t i l l e d from i t .

The v is c o u s r e s id u e was n o t

v o l a t i l e a t 5 mm. and c o u ld n o t be i d e n t i f i e d . D e h y d ro h a lo g e n a tio n o f A c e ty l C h lo r i d e .-

One h u n d red grams

( l m ole) o f t r i e t h y l a m i n e was added s lo w ly to a n i c e - c o l d s o l u t i o n o f 1*00 m l. o f anh y d ro u s e t h e r and 7 0 .6 g . ( 0 .9 m ole) o f a c e t y l c h l o r i d e . A rrangem ents w ere made t o p a s s a l l uncondensed g a s e s i n t o an e t h e r a n ilin e s o lu tio n a t 0 ° .

The r e a c t i o n was a llo w e d t o s i t f o r t h r e e h o u rs ,

and th e n 20 m l. o f c o n c e n tr a te d h y d r o c h lo ric a c id and $0 g . o f e th a n o l w ere added, and th e s o l u t i o n was a llo w e d to s i t o v e r n ig h t.

The heavy

p r e c i p i t a t e was removed by f i l t r a t i o n , d is s o lv e d i n w a te r , and th e aqueous s o l u t i o n e t h e r - e x t r a c t e d .

The combined f i l t r a t e and e t h e r ex­

t r a c t was d r ie d and th e n r e c t i f i e d t o g iv e 21* g . ( 1*3#) o f a c e t o a c e t i c e s t e r , i d e n t i f i e d by o d o r and th e co p p er c h e l a t e .

The p o t r e s id u e o f

th e r e c t i f i c a t i o n s o l i d i f i e d and was i d e n t i f i e d as th e e th y l e s t e r o f d e h y d r a c e tic a d d a f t e r p u r i f i c a t i o n , m .p . 93°•

The e t h e r - a n i l i n e s o lu ­

t i o n was d i s t i l l e d t o 200° and th e r e s i d u e was i d e n t i f i e d a s a c e t a n i l i d e , m .p . 1 1 3 °. D e h y d ro h a lo g e n atio n o f D if lu o r o a c e ty l C h l o r id e .-

A $ 0 0 -m l. ,

3-n e c k e d f l a s k w ith ground g l a s s j o i n t s was equipped w ith a s e a le d s t i r r e r , d ro p p in g f u n n e l, and r e f l u x c o n d e n s e r.

The r e f l u x c o n d e n se r

was c o n n e c te d i n s e r i e s w ith a Dry I c e - t r i c h l o r o e t h y l e n e t r a p , fo llo w e d by a l i q u i d a i r t r a p .

F o r ty grams o f d i f l u o r o a c e t y l c h l o r i d e ( p re p a r e d

i n 68.1*# y i e l d b y t h e method o f Brown^) was added s lo w ly to 37*1* g . o f t r i e th y l am ine and 120 g . o f anhydrous e t h e r .

The r e a c t i o n was allo w ed

t o s i t o v e r n ig h t a t 0 ° , and th e n t h e e t h e r e a l s o lu t i o n was removed by in v e r te d f i l t r a t i o n .

The e t h e r was e v a p o ra te d u n d e r vacuum t o le a v e

x x ii

30 g« o f a d a rk brow n, v is c o u s l i q u i d b e li e v e d t o b e a low —m o le c u la r — w e ig h t p o ly m er o f d if l u o r o k e t e n e . P y r o ly s is o f D if lu o r o k e te n e P o ly m e r.-

A s ta n d a r d lam p f o r t h e

p y r o l y s i s o f d ik e te n e s was p r e p a re d 10 and a rra n g e m e n ts w ere made t o p a s s

1 0 . "O rg an ic R e a c tio n s " , V o l. I l l , John W iley and Sons, I n c . , New York, N. Y ., 191*7, P* 136.

any e v o lv e d g a s e s th ro u g h a w a te r - c o o le d c o n d e n se r and t r a p . Dry I c e t r i c h l o r o e t h y l ene t r a p , b e n z e n e - a n ilin e s o l u t i o n . Dry I c e - t r i c h l o r o e t h y le n e t r a p , and l i q u i d a i r t r a p i n th e o r d e r g iv e n .

The polym er was p la c e d

i n t h e lam p, and th e te m p e ra tu re o f th e s u rro u n d in g o i l b a th r a i s e d g ra d ­ u a l l y u n t i l co m p lete c h a r r in g o c c u rre d .

No c o n d e n sa te was found i n

any

o f th e t r a p s , b u t a heavy p r e c i p i t a t e was p r e s e n t i n th e b e n z e n e - a n ilin e s o lu tio n .

T h is was rem oved by f i l t r a t i o n , and th e b e n z e n e - a n ilin e s o lu ­

t i o n p ro c e s s e d a s b e f o r e f o r d i f i u o r o a c e t a n i l i d e , b u t none c o u ld be fo u n d .

The p r e c i p i t a t e d m a t e r ia l i s b e lie v e d to be th e a n i l i n e - s i l i c o n

t e t r a f l u o r i d e com plex s in c e s e v e re e tc h in g o f th e g la s s lam p o c c u re d , and s i l i c o n t e t r a f l u o r i d e w ould n o t be tra p p e d i n th e Dry I c e - t r i c h l o r o e th y le n e t r a p im m e d ia te ly p re c e d in g th e b e n z e n e - a n ilin e s o l u t i o n . P r e p a r a tio n o f D i f lu o r o a c e ty lp h th a lim id e . -

A 200- m l. , S o x h le t

e x t r a c t o r w ith an Alundxin cup was m ounted o v e r a 5>00-ml. p o t and eq u ip p ed w ith a r e f l u x c o n d e n se r surm ounted by a d ro p p in g fu n n e l and a Dry I c e r e f l u x c o n d e n s e r.

A s o l u t i o n o f 2$ .6 g . o f d i f l u o r o a c e t y l c h l o r id e

100 m l. o f anhydrous b en zen e was d ropped p h th a lim id e c o n ta in e d i n t h e Alundun cu p .

s lo w ly on t o 1*1 .2

and g . o f p o ta ss iu m

The s o l u t i o n was allo w ed to

s ta n d i n c o n ta c t w ith th e p o ta ss iu m p h th a lim id e f o r one h o u r, and th e n

x x iii

e x t r a c t i o n was i n i t i a t e d and c o n tin u e d f o r s i x and o n e - h a lf h o u r s .

The

s o l u t i o n ( I ) i n t h e p o t was d e c a n te d ( a l l d é c a n ta tio n s and a d d i t i o n s w ere done i n a d ry -b o x ) i n t o an E rlen m ey er f l a s k and p r o te c t e d from m o is tu re w ith a c a lc iu m c h l o r id e d ry in g t u b e .

Two h u n d red m i l l i l i t e r s o f f r e s h

b en zen e ( I I ) was added to t h e p o t , and th e e x t r a c t i o n was c o n tin u e d f o r an a d d i t i o n a l tw e lv e h o u r s .

The ben zen e s o l u t i o n ( I ) was c o o le d , and

th e m o th er l i q u o r d e c a n te d from th e c r y s t a l s w hich form ed.

Anhydrous

b en zen e (200 m l . ) was ad d ed , and th e s o l u t i o n was r e f l u x e d u n t i l a l l th e c r y s ta ls d is s o lv e d .

The s o l u t i o n was c o o le d , d e c a n te d from th e p r e c i ­

p i t a t e d d if l u o r o a c e t y l p h t h a l i m i d e , and th e r e s i d u a l m o th er l i q u o r evapo­ r a t e d a t 5 mm. on a steam b a t h .

The ben zen e s o lu t i o n ( I I ) was p ro c e s s e d

i n t h i s same m anner, and t h e com bined c r y s t a l s (2 3 .2 g . , m .p . 11*8- 9° ) w ere t r a n s f e r r e d t o a t i g h t l y capped b o t t l e .

T h is i s a c o n v e rs io n o f

79.U #. P y r o ly s i s o f D i f lu o r o a c e ty lp h th a lim id e .-

The p y r o l y s i s was

c a r r i e d o u t i n a 200- m l. d i s t i l l i n g f l a s k w ith an i n l e t f o r n itr o g e n s l i g h t l y b elo w t h e t a k e - o f f arm .

A th erm om eter was p la c e d i n th e f l a s k

w ith t h e b u lb one in c h above th e m a te r ia l t o be p y ro ly z e d .

The ev o lv ed

g a s e s w ere l e d th ro u g h a w a te r -c o o le d c o n d en ser and t r a p , a Dry I c e t r i c h l o r o e t h y l ene t r a p , a b e n z e n e - a n ilin e s o l u t i o n , a Dry I c e - t r i c h l o r o ­ e th y l ene t r a p , and a l i q u i d a i r t r a p i n th e o r d e r g iv e n .

The f l a s k was

c h a rg e d w ith 1 6 . 1* g . o f d i f l u o r o a c e ty lp h th a lim id e ; and w h ile d ry n i t r o ­ gen was p a s s e d th ro u g h th e sy stem , th e te m p e ra tu re was s lo w ly r a i s e d by means o f a Wood1s m e ta l b a th t o 31*0°, th e i n s i d e f l a s k te m p e ra tu re b e in g 2 6 0 °.

A f te r no more r e a c t i o n was a p p a r e n t, th e p y r o ly s is was s to p p e d ,

and th e v a r io u s t r a p s w ere i n s p e c t e d .

No p ro d u c t was found i n any t r a p

e x c e p t t h e f i r s t Dzy I c e - t r i c h l o r o e t h y l e n e t r a p w hich c o n ta in e d 3 m l. o f a c l e a r l i q u i d w ith an o d o r s i m i l a r t o d i f l u o r o a c e t i c a c id .

The l i q u i d

d i s t i l l s a t a p p ro x im a te ly 0- 10° , r e a c t s w ith a n i l i n e to g iv e a n i l i n e h y d ro f l u o r i d e and d i f i u o r o a c e t a n i l i d e , r e a c t s v i o l e n t l y w ith w a te r , and g iv e s a p o s i t i v e f l u o r i n e t e s t w ith s a t u r a t e d c a lc iu m c h lo r id e s o l u t i o n . No o t h e r p ro d u c t was i s o l a t e d . P r e p a r a tio n o f 1 , 1 - D if lu o r o a c e to n e . -

The m ethod d e s c r ib e d b y

H e n n e ^ was u se d w ith th e e x c e p tio n t h a t th e i n te r m e d ia te ">, > - d i f l u o r o -

1 1 . Henne and Newman, J . Am. Chem. S o c . , 69» 1819 (I9 li7 ) •

a c e t o a c e t a t e was n o t i s o l a t e d .

By t h i s m ethod, 12h 6 * (1 m ole) o f e th y l

d i f l u o r o a c e t a t e was condensed w ith 98 g . (1 m ole) o f e t h y l a c e t a t e .

The

r e s u l t i n g s o l u t i o n c o n ta in in g th e s o lv e n t and th e c ru d e e n o la te s a l t was t r a n s f e r r e d t o a 1 - l i t e r f l a s k eq u ip p ed w ith a 2- f o o t , s p ir a l- p a c k e d r e f l u x c o n d e n s e r w ith a w a te r j a c k e t s e t a t

The e th a n o l and u n ­

r e a c t e d e s t e r w ere rem oved a t re d u c e d p r e s s u r e , and 72$ g . o f 20% s u l f u r i c a c id was added to t h e p o t .

1 w a te r -c o o le d c o n d e n se r s e t f o r down­

w ard d i s t i l l a t i o n was a tta c h e d t o th e packed r e f l u x c o n d e n se r, and any uncon d en sed v a p o rs w ere p a s s e d i n t o a Dry I c e - t r i c h l o r o e t h y l ene t r a p . The s o l u t i o n was r e f l u x e d f o r f o u r d ay s, and th e n th e t o t a l d i s t i l l a t e was r e c t i f i e d t o g iv e $0 g . o f 1 , 1 - d if lu o r o a c e to n e , b . p . U6- 7° . ($ 2/6) . I V r o l y s i s o f 1 , 1 - D if lu o r o a c e to n e . -

The equipm ent u se d i n t h i s

e x p e rim e n t c o n s is t e d o f a s ta n d a r d k e te n e lam p.

12

T h is was c o n n e c te d t o

1 2 . "O rg an ic R e a c tio n s " , V o l. I l l , John W iley and S ons, I n c . . , New York, N. Y ., 19U7, p . 1 3 2 .

XXV

two v e r t i c a l c o n d e n s e rs fo llo w e d b y a t r a p im m ersed i n i c e . d en sed g a s e s w ere l e d th ro u g h an e t h e r - a n i l i n e s o l u t i o n .

The uncon­

F i f t e e n grains

o f 1 , 1 - d if l u o r o a c e t o n e was p la c e d i n th e p o t and h e a te d t o a r a p id r e f l u x o v e r th e f il a m e n t .

E v o lu tio n o f g ases began when th e f ila m e n t was h e a te d

t o a d u l l r e d , w ith t h e im m ed iate f o rm a tio n o f a w h ite p r e c i p i t a t e i n th e e th e r - a n ilin e s o lu tio n .

The r e f l u x i n g was c o n tin u e d u n t i l a l l t h e d i -

f lu o r o a c e to n e was p y r o ly z e d .

On a n a ly s is o f th e e t h e r - a n i l i n e s o l u t i o n ,

no d i f i u o r o a c e t a n i l i d e c o u ld b e fo u n d .

The p r e c i p i t a t e i n th e e t h e r -

a n i l i n e s o l u t i o n was n o t c h a r a c t e r iz e d b u t was u n d o u b te d ly a n i l i n e h y d ro flu o rid e .

R e p e titio n s o f t h e r e a c t i o n gave th e same r e s u l t s . P y r o ly s i s o f D i f lu o r o a c e tic A cid . -

U sing th e same equipm ent

and te c h n iq u e a s ab o v e, 2$ g . o f d i f l u o r o a c e t i c a c id was p y ro ly z e d th ro u g h t h e lam p.

No t r a c e o f d i f i u o r o a c e t a n i l i d e was fo u n d .

The o n ly

compound i s o l a t e d was th e u s u a l p r e c i p i t a t e i n th e b e n z e n e - a n ilin e s o lu ­ tio n .

T h is was a n a ly z e d f o r s o lu b le f l u o r i d e io n c o n te n t5 3 6 .1 $ .

S in c e

th e p o t d e c re a s e d 3 .3 g . i n w e ig h t and 3 g . o f t h e p r e c i p i t a t e was form ed i n th e b e n z e n e - a n ilin e s o l u t i o n , t h i s a c c o u n ts f o r 100# o f th e f l u o r i n e i n t h e decom posed d i f l u o r o a c e t i c a c i d .

Summary The p r e p a r a t i o n o f d if lu o r o k e te n e h as b een a tte m p te d by ev e ry m ethod b e lie v e d f e a s i b l e by th e i n v e s t i g a t o r s .

I n no c a s e was th e r e

any i n d i c a t i o n t h a t d if lu o r o k e te n e had been p ro d u ced , th e u s u a l p ro d u c ts o f t h e r e a c t i o n s b e in g e i t h e r po lym ers o r d ec o m p o sitio n p r o d u c ts .

Sev­

e r a l new compounds have b ee n p r e p a re d i n th e c o u rse o f th e i n v e s t i g a t i o n .

X

PREPARATION AND PROPERTIES OF CERTAIN FLUORINE-CONTAINING ESTERS AND KETONES

INTRODUCTION The o r i g i n a l p u rp o se o f t h i s r e s e a r c h was th e p r e p a r a t i o n o f d if lu o r o k e te n e .

No d ih a lo g e n a te d k e te n e h a s e v e r b een r e p o r te d , and th e

p r o p e r t i e s o f such a compound sh o u ld be o f c o n s id e r a b le i n t e r e s t b o th from a t h e o r e t i c a l and p r a c t i c a l v ie w p o in t.

D iflu o r o k e te n e s h o u ld p o s s e s s

th e u s u a l r e a c t i v i t y o f k e te n e , g iv in g th e u s u a l r e a c t i o n s o f k e te n e s , and i n a d d i t i o n i t seemed p o s s ib le t h a t th e p re s e n c e o f th e s tr o n g l y e l e c t r o ­ n e g a tiv e f l u o r i n e atoms would n o t o n ly enhance th e a c t i v i t y o f th e k e te n e , b u t m ig h t c o n c e iv a b ly le a d t o r e v e r s e a d d i tio n w ith r e a c t a n t s . A lthough d if lu o r o k e te n e was n o t p r e p a re d , one o f th e r e a c t i o n s i n v e s t i g a t e d i n t h e p r e p a r a tio n o f a p o s s i b le in te r m e d ia te f o r t h i s s y n th e s i s p ro v ed o f s tr o n g i n t e r e s t from th e v ie w p o in t o f t h e o r e t i c a l c h e m is tr y .

Rhen th e a tte m p t t o p r e p a re d if lu o r o k e te n e was abandoned,

t h i s r e a c t i o n was f u r t h e r i n v e s t i g a t e d , th e m a jo r ity o f t h i s t h e s i s b e in g co n cern ed w ith th e a l k a l i n e c o n d e n s a tio n s o f e th y l d i f h i o r o a c e t a t e i n th e p re s e n c e o f sodium h y d r id e . From a t h e o r e t i c a l v ie w p o in t v e ry l i t t l e i s known c o n c e rn in g th e a l k a l i n e c o n d e n s a tio n s o f f lu o r i n a t e d e s t e r s .

E th y l t r i f l u o r o a c e t a t e

and e t h y l d i f l u o r o a c e t a t e have been s u c c e s s f u lly condensed w ith e t h y l a c e t a t e and s e v e r a l k e to n e s (11,19*1*7)> b u t p r i o r a tte m p ts a t th e s e l f ­ c o n d e n s a tio n o f f lu o r i n e - c o n t a i n in g e s t e r s by th e a c e to a c e t i c e s t e r con­ d e n s a tio n have been u n s u c c e s s fu l (1 9 )•

I n a mixed a c e t o a c e ti c e s t e r

c o n d e n s a tio n f o u r p ro d u c ts a r e u s u a ll y p o s s i b l e — two mixed c o n d e n s a tio n

p r o d u c ts , and two s e lf - c o n d e n s a tio n p r o d u c t s .

I n p r i o r work, no one h a s

r e p o r te d c o n d en sin g a f lu o r i n e - c o n t a i n i n g e s t e r so t h a t th e f l u o r i n e i s i n th e a lp h a p o s i t i o n o f th e y ^ - k e t o e s t e r .

The bromo and c h lo ro d e r i ­

v a t i v e s w ith brom ine o r c h l o r in e i n th e a lp h a p o s i t i o n have b een p r e ­ p a re d ( 1 , 5 ) b u t u n l i k e f l u o r i n e , th e s e h a lo g e n s a r e e a s i l y rem oved, and a r e removed i n many o f th e r e a c t i o n s a tte m p te d w ith such compounds.

The

two f lu o r i n e - c o n t a i n i n g / ^ - k e t o e s t e r s w hich have been p re p a re d show r e ­ m ark ab le s t a b i l i t y and an u n u s u a lly r e a c t i v e k e to g ro u p .

C o n seq u en tly ,

i t was d e c id e d t o s tu d y th e e f f e c t o f f l u o r i n e i n th e a lp h a p o s i t i o n i f such a compound c o u ld be made. d e r iv a b le from any such

I n a d d iti o n , s e v e r a l compounds sh o u ld be

- k e to e s t e r .

The a c id i t s e l f s h o u ld p o s s e s s

i n t e r e s t i n g p r o p e r t i e s , h a v in g two v e ry r e a c t i v e g ro u p s, and th e f l u o r i n e c o n ta in in g a c e to n e s s h o u ld b e u n u s u a l i n th e r e a c t i v i t y o f th e k e to group E th y l c t ,c t ,> ,> - t e t r a f l u o r o a c e to a c e t a t e h a s now b e e n p re p a re d i n good y i e l d s and i t s p r o p e r t i e s and r e a c t i o n s s tu d i e d .

A lthough a tte m p ts

a t c o n d e n sin g e t h y l d i f l u o r o a c e t a t e w ith o th e r e s t e r s so t h a t th e f l u o r i n e atom s w ere i n th e a lp h a p o s i t i o n were u n s u c c e s s f u l, th e i n v e s t i ­ g a tio n o f t h i s r e a c t i o n l e d to s e v e r a l i n t e r e s t i n g compounds and demon­ s t r a t e d th e u n u s u a l r e a c t i v i t y o f a k e to group w ith f l u o r i n e a d ja c e n t to i t on b o th s i d e s .

P a rt I PREPARATION AND REACTIONS OF ETHYL

,r-TETRAFLUOROACETOACSTATE

u

I n tr o d u c tio n The p u rp o se o f t h i s p a r t i c u l a r r e s e a r c h was t o p r e p a r e a e s t e r c o n ta in in g f l u o r i n e i n th e a lp h a and gamma p o s i t i o n s .

- k e to

The h a lo g e n -

a te d / 9 - k e t o e s t e r s g iv e n i n T a b le I have b een p re p a re d p r e v io u s ly and c e r ta in o f th e i r re a c tio n s in v e s tig a te d . No r e c o r d was found o f any a c e to a c e tic e s t e r c o n ta in in g more th a n t h r e e h a lo g e n atom s, o r one i n w hich b o th a lp h a p o s it i o n s w ere sub­ s t i t u t e d a s w e ll a s one o r more o f th e gamma p o s i t i o n s .

S e v e r a l a tte m p ts

to p r e p a re such compounds w ere u n s u c c e s s fu l ( 9 , 19) . A rn d t, Loewe, and Capuano (2 ) found t h a t r e a c t i o n s o f compounds o f t h e s t r u c t u r e R-CO-CR' R* ' -COgR* *' a r e g r e a t l y in f lu e n c e d by th e n a tu r e o f R, R1, and RM ; and t o a l e s s e r e x te n t by R, u .

I f R i s a m ethyl

g ro u p , f o r exam ple, th e s u b s t i t u t i o n o f hydrogen by h a lo g e n d e c re a s e s th e e l e c t r o n d e n s ity o f th e c a rb o n y l carb o n atom , making i t r e l a t i v e l y more p o s i t i v e .

T h is fa v o rs fo rm a tio n o f th e e n o l form o f th e e s t e r and

in c r e a s e s th e ten d e n c y f o r th e fo rm a tio n o f h y d r a te s , a l c o h o la te s , k e t a l s , and e n o l e t h e r s .

I n t h i s r e s p e c t i t i s v e r y s i m i l a r to c h l o r a l .

As e v i ­

dence o f i t s s t a b i l i t y , th e h y d ra te o f m ethyl T ^ y / y - t r i c h l o r o a c e to a c e t a t e g iv e s a r e d c o lo r w ith f e r r i c c h lo r id e o n ly a f t e r s ta n d in g f o r some tim e , a lth o u g h p u re m ethyl Y , y ,Y - t r i c h l o r o a c e t o a c e t a t e g iv e s an im m ediate d a rk re d c o lo r.

S im i l a r l y , m ethyl " Y /y ,Y - tr ic h lo r o a c e to a c e ta te i s d i f f i c u l t

to p u r i f y b ec a u se o f th e s t a b i l i t y o f th e a lc o h o la te and th e e q u ilib r iu m betw een k e to , e n o l, and a lc o h o l a t e .

D é s ir a n t (11) found t h a t e th y l > , y -

d i f l u o r o a c e t o a c e t a t e form s a s t a b l e h y d ra te ( n o t i s o l a t e d ) , and S w artz (U7 ) fo u n d t h a t e t h y l 'y ," y ,y - t r i f l u o r o a c e t o a c e t a t e h as a s tr o n g te n d e n c y to h y d r a t e .

E th y l o f-b ro m o a c e to a c e ta te r e a r r a n g e s t o e t h y l

-b ro m o a c e to -

5

T a b le I H alo g en -C o n ta in in g A c e to a c e tic E s te r s

I

H

E s te r c i. - e h l o r o a c e t o a c e ta te

Form ula

R e f.

c h 3c o c h c ic o 2c 2h^

1

2 . E th y l CL -b ro m o a c e to a c e ta te

CH^COCHBrCO^CjH^

5 , 1 3 , 2h

3* E th y l cc ^ c - d i e h lo r o a c e to a c e t a te

ch3c o c c i2c o 2c 2h^

27

U* E th y l

CH^COCBrgCOgCgH^

5

£• E th y l QC, > - d i e h lo ro ae e to a c e t a te

ch 2c ic o c h c ic o 2c 2h^

53

6 . E th y l " V -c h lo ro a c e to a c e ta te

CH2C1C0CH2C02C2H£

18

7* E th y l 7^-bronioac e to a c e t a t e

CH2BrC0CH2C02C2H^

8, 37

8 . E th y l

c h f 2coch2co 2c 2h5

11, 19

tric h lo ro a c e to a c e ta te

c c i 3coch2co 2c 2h^

2, 39

trib r o m o a c e to a c e ta te

CBr3C0CH2C02C2H5

39

c f 3coch2co 2c 2h^

19, k l

,e c -d ib ro m o a c e to a c e ta te

> ,> - d i f lu o r o a c e t o a c e t a te

9* E th y l 1 0 . E th y l >

1 1 . E th y l > , > , > - t r i f l u o r o a c e t o a c e t a t e

6

a c e t a t e ( 13>2U)> and many

h a lo g e n a te d

—k e to e s t e r s r e a c t a lm o st

q u a n t i t a t i v e l y w ith h y d ra z in e h y d r a te form in g t h e u n s u b s t i t u t e d a c e to ­ a c e tic e s te r (2 7 ).

S i m i l a r l y , t h e r e a c t i o n s o f ,> - d if lu o r o a c e to a c e ta te .

I n th e f o rm a tio n o f t h i s

/d - k e to e s t e r , e t h y l d i f l u o r o a c e t a t e a c te d as th e ••a c y la tin g " e s t e r . T h is , w ith th e a d d i t i o n a l f a c t t h a t e s t e r s o f d i f l u o r o a c e t i c a c id c o u ld n o t be fo rc e d t o u ndergo s e lf - c o n d e n s a tio n s , l e d to th e c o n c lu s io n t h a t sodium e th o x id e was to o weak a b a se to e f f e c t e n o l i z a t i o n o f th e

#-

hyd ro g en i n e th y l d i f l u o r o a c e t a t e . Sodium h y d r id e , how ever, i s a much s tr o n g e r b a s e , and r e c e n t i n v e s t i g a t i o n s o f th e u s e o f sodium h y d rid e i n a c e t o a c e ti c e s t e r conden­ s a ti o n s have shown t h a t t h i s b a se q u i te o f te n p e r m its c o n d e n s a tio n i n good y i e l d s where sodium e th o x id e had p r e v io u s ly f a i l e d (17>U5»U6).

When

t h i s b a s e was u se d u n d e r c e r t a i n c o n d itio n s , th e s e lf - c o n d e n s a tio n p r o ­ d u c t o f e t h y l d i f l u o r o a c e t a t e , e th y l

c l

, * ,> ,> - t e t r a f l u o r o a c e t o a c e t a t e ,

was o b ta in e d i n good y i e l d s , u n d o u b te d ly th ro u g h th e f o llo w in g s e r i e s o f r e a c t i o n s , s in c e th e mechanism o f th e a c e to a c e tic e s t e r c o n d e n s a tio n h a s b een s tu d ie d r a t h e r e x t e n s iv e ly . 1.

CHPgCOgCgHg +

NaH ---» CFgCOgCgH^ +

2.

CHFgCOgCgHjj +

CFgCOgCgHç

Na"'" -f Hg

CHFgCOCFgCOgCgH^ >

OCgHç

L a t e r work i n t h i s l a b o r a t o r y h as shown t h a t s t i l l a t h i r d s te p i s i n ­ c lu d e d i n t h i s r e a c t i o n —t h e a d d it io n o f th e l i b e r a t e d e th o x id e i o n to th e c a rb o n y l group o f th e k e to n e . 3.

GHFg—CO—

OCgH^

OCgH^ -

^ CHFg—C—CF^—CO—OCgH^

6° ^ The p r o o f and s i g n i f i c a n c e o f t h i s s te p i s g iv e n l a t e r i n t h i s t h e s i s .

12

E th y l d i f l u o r o a c e t a t e r e a c t s w ith sodium h y d r id e o n ly s lo w ly a t o room te m p e r a tu re s , b u t r a p i d l y and e x o th e rm a lly a t te m p e r a tu re s above 90 i n m ost s o lv e n ts to r e l e a s e hydrogen as shown b y e q u a tio n 1 .

The seco n d

s te p i s a p p a r e n tly even more r a p i d th a n t h e f i r s t , s in c e e x c e l l e n t y i e l d s o f th e / 5 - k e t e e s t e r w ere o b ta in e d when th e r e a c t i o n was s to p p e d th e i n s t a n t hydrogen c ea sed to be e v o lv e d .

T h is may be due t o th e f a c t t h a t

th e f i r s t s te p i s a l i q u i d - s o l i d r e a c t i o n w h ile th e seco n d i s a homo­ geneous r e a c t i o n .

The c h o ic e o f s o lv e n ts i s e x tre m e ly im p o r ta n t.

Ben­

zen e, e t h e r , d ib u t y l e t h e r , d io x a n e , e t h y l c a r b o n a te , e th y l c h lo r o c a r b o n a te , and e x c e s s e th y l d i f l u o r o a c e t a t e w ere t r i e d a s s o lv e n ts , and o n ly i n e x c e s s e t h y l d i f l u o r o a c e t a t e o r d io x an e w ere a p p r e c ia b le y i e l d s o f th e d e s ir e d p ro d u c t i s o l a t e d .

The r e f l u x te m p e ra tu re o f e t h e r i s to o

low t o p e r m it th e e n o l i z a t i o n s te p , and b enzene seems t o i n h i b i t th e r e a c t i o n , making i t p ro c ee d s lo w ly and w ith much d e c o m p o sitio n .

D i­

b u ty l e t h e r g iv e s low y i e l d s , e th y l c a rb o n a te c a u se s p o ly m e r iz a tio n , and d io x an e s u f f e r s from th e d is a d v a n ta g e o f b e in g w a te r s o lu b le so t h a t s e p a r a t i o n o f th e d e s ir e d p ro d u c t i s v e ry d i f f i c u l t .

However, i n e x c e ss

e th y l d i f l u o r o a c e t a t e , y i e l d s o f 78% have b een o b ta in e d .

The y i e l d s

v a r y i n v e r s e l y w ith th e s i z e o f th e p a r t i c l e s o f sodium h y d r id e , and th e b e s t y i e l d s w ere o b ta in e d w ith v e r y f i n e l y d iv id e d sodium h y d r id e .

The

g r in d in g o f th e sodium h y d rid e may be acco m p lish ed s a f e l y i n a d ry -b o x p ro v id e d no more th a n 6% b y volume o f oxygen i s p r e s e n t (29)♦

A b e tte r

m ethod i s t o p la c e s e v e r a l g la s s m arb le s i n th e r e a c t i o n f l a s k and g r in d th e sodium h y d rid e i n s o l u t i o n .

The c o u rs e o f th e r e a c t i o n i s fo llo w e d

b y m easu rin g th e amount o f hydrogen e v o lv e d , and c a r e m ust be ta k e n to re d u c e t h e te m p e ra tu re o f th e s o lu t i o n n e a r c o m p le tio n t o p r e v e n t

13

p o ly c o n d e n s a tio n s .

Even th e n , c o n s id e r a b le b y - p ro d u c ts o f w a te r - s o lu b le ,

p o ly m e ric m a t e r i a l s a r e form ed. The r e a c t a n t s , o f c o u r s e , sh o u ld b e an h y d ro u s, s in c e t r a c e s o f w a te r r e a c t w ith t h e b a s e t o form sodium h y d ro x id e .

The r e a c t i o n i s ru n

p r e f e r a b l y u n d e r n i t r o g e n , s in c e t h e p re s e n c e o f oxygen i s b o th d a n g e r­ ous and u n d e s i r a b l e . The p r o d u c t, e t h y l « .,,>- t e t r a f l u o r o a c e t o a c e t a t e , i s d i f f i ­ c u l t to o b ta in p u re .

R e c t i f i c a t i o n i s u s u a ll y accom panied by a r i s e i n

te m p e r a tu re fo llo w e d b y a d rop i n te m p e ra tu re below t h a t b e g in n in g th e r e c t i f i c a t i o n w ith sim u lta n e o u s in c r e a s e i n p o t te m p e r a tu re .

E xam inatio n

o f t h e r e f r a c t i v e in d e x o f th e v a r io u s c u ts o f th e r e c t i f i c a t i o n h a s shown t h a t th e compound i s n o t p u re a f t e r one r e c t i f i c a t i o n , a lth o u g h r e p e a te d r e c t i f i c a t i o n o f th e same c u ts te n d to b r in g th e r e f r a c t i v e in d e x o f th e v a r io u s f r a c t i o n s i n t o c l o s e r ag re e m e n t.

From t h i s and

th e v a r io u s p r o p e r t i e s o f th e e s t e r , i t h a s been co n clu d ed t h a t e i t h e r a h e m ik e ta l o r a h y d r a te i s p r e s e n t i n e q u ilib r iu m w ith t h e e s t e r .

T h is

a g r e e s w ith th e f a c t t h a t th e e s t e r m ixes w ith w a te r o r a lc o h o l w ith l i b e r a t i o n o f c o n s id e r a b le h e a t .

A ttem p ts t o i s o l a t e t h e h y d r a te by

s u b lim a tio n have b een u n s u c c e s s f u l. E x p e rim e n ta l A SOO-ml. , 3 -n ec k ed f l a s k was eq u ip p ed w ith a d ro p p in g f u n n e l, s e a le d s t i r r e r , and r e f l u x c o n d e n s e r.

The sy stem was p r o te c te d

from m o is tu re w ith a c a lc iu m c h lo r id e tu b e , and arra n g e m e n ts were made t o c o l l e c t th e e v o lv e d h y d ro g en b y d is p la c e m e n t o f w a te r . was flam e d d r y , and th e a i r was d is p la c e d by n i t r o g e n .

The system To th e f l a s k

l ii

w ere th e n added 10*38 g . ( 0 .U3 m ole) o f sodium h y d rid e and 158 g* (1* 2 ? m oles) o f e th y l d i f l u o r o a c e t a t e .

E ig h t g l a s s m a rb le s w ere added,

and t h e s o lu t i o n was s t i r r e d t o a llo w g r in d in g o f th e sodium h y d r id e i n s o lu tio n .

The s o lu t i o n was r e f lu x e d f o r one and one—h a l f h o u rs d u rin g

w hich tim e 9*7 l i t e r s o f h ydrogen was c o l l e c t e d ( l 00>o o f th e o r y ) •

The

s o l u t i o n was c o o le d q u ic k ly and p o u red i n t o a b e a k e r c o n ta in in g c ru sh e d i c e and 20 g . o f a c e t i c a c i d .

The tw o -p h ase s o l u t i o n was t r a n s f e r r e d to

a s e p a r a to r y fu n n e l and e x t r a c t e d w ith 200 m l. o f e t h e r .

F our more e x ­

t r a c t i o n s w ith d im in is h in g q u a n t i t i e s o f e t h e r were made, and th e com­ b in e d e t h e r e x t r a c t s w ere d r ie d o v e r sodium s u l f a t e fo llo w e d by D r i e r i t e . Vacuum d i s t i l l a t i o n fo llo w e d by vacuum r e c t i f i c a t i o n gave 61*.9 g . o f e t h y l e t , o t,> ,Y - te tr a f lu o r o a c e to a c e ta te , b . p . 3 9 -3 2 ° /3 mm., n^°1.35U 2, and 17 g . o f e t h y l d i f l u o r o a c e t a t e .

T h is i s a y i e l d o f 7W& b a se d on

sodium h y d r id e , o r 5 6 . 5/6 b a se d on e t h y l d i f l u o r o a c e t a t e . A n a l. C a lc d . f o r C^H^F^O^: C, 35*65; H, 2 .9 9 ; F, 37*60. Founds C, 35*6; H, 2.985 F, 37*9. R e a c tio n s o f E th y l ec,et,"y,>- T e tr a f lu o r o a c e to a c e ta te D is c u s s io n D e riv a tiv e s .

A su rv e y o f th e l i t e r a t u r e h as d is c lo s e d few

in s t a n c e s i n w hich th e u s u a l d e r i v a t iv e s f o r an e s t e r o r k e to group have b e e n p re p a re d f o r a h a lo g e n a te d /& - k e to e s t e r .

TSherever p o s s ib le

th e e s t e r s a r e i d e n t i f i e d th ro u g h t h e i r co p p er c h e l a t e s .

However, i n

th e c a s e o f e t h y l oL,,>- t e t r a f l u o r o a c e t o a c e t a t e , th e p r e p a r a tio n o f th e c o p p er c h e l a t e i s im p o s s ib le s in c e t h i s compound h a s no ^ - h y d r o g e n .

15

I t h sis b s e n found t h s t roost

[email protected]&t©d s c ô t o â c s t i c © s ts rs les© th©

h a lo g e n when r e a c t e d w ith h y d ra z in e (27) •

T h is i s a p p a r e n tly t r u e a l s o

w ith th e a l k y l - and a r y l - s u b s t i t u t e d h y d r a z in e s , s in c e a tte m p te d p r e ­ p a r a t i o n s o f t h e 2 , U -d in itro p h e n y lh y d ra z o n e , th e se m ic a rb a z o n e , and th e h y d razo n e o f e t h y l «•,•,>- t e t r a f l u o r o a c e t o a c e t a t e w ere u n s u c c e s s f u l, a lth o u g h i n th e l a s t two c a s e s some r e a c t i o n d id ta k e p l a c e , s in c e a s a l t - l i k e o r g a n ic compound was i s o l a t e d .

The s t r u c t u r e o f th e s e com­

pounds c o u ld n o t b e d e te rm in e d , how ever.

A ttem p ts t o p r e p a r e o t h e r

d e r i v a t i v e s , such as th e oxim e, w hich s h o u ld n o t c a u s e rem oval o f th e f l u o r i n e n o r g iv e p y ra z a lo n e s o r r i n g compounds w ere u n s u c c e s s f u l. S i m i l a r l y , t h e p r e p a r a t i o n o f th e b en zy lam id e was a tte m p te d w ith o u t su ccess.

I t h a s b e e n r e p o r te d t h a t c e r t a i n o f th e s e h a lo g e n a te d / ^ - k e t o

e s t e r s do n o t r e a c t a s e x p e c te d due t o th e fo rm a tio n o f th e h y d r a te o r th e a lc o h o l a t e , w hich e f f e c t i v e l y p r e v e n ts r e a c t i o n o f th e k e to group a s su ch ( 2 ) .

W hile t h i s may o f f e r an e x p la n a tio n f o r th e f a i l u r e o f

d e r i v a t i v e s to form i n w a te r o r a lc o h o lic s o lu t i o n , i t does n o t e x p la in why th e 2, U -d in itro p h e n y lh y d ra z o n e was n o t o b ta in e d when an a tte m p t was made t o p r e p a r e t h e d e r i v a t i v e i n anhydrous d io x a n e .

The 2 ,U - d i n i t r o -

p h e n y lh y d ra z in e was re c o v é re d u n r e a c te d . P r e p a r a t i o n o f B < ,o L ,v ,y -T e tra flu o ro a c e to a c e tic A c id .

The

m a jo r ity o f t h e h a lo g e n - c o n ta in in g @ - k e to e s t e r s have b een h y d ro ly z e d w ith l i t t l e d i f f i c u l t y .

T h is i s t r u e a ls o o f e th y l > , > , > - t r i f l u o r o -

a c e t o a c e t a t e , a lth o u g h h y d r o ly s is o f t h e e s t e r w ith c o n c e n tr a te d h y d ro ­ c h l o r i c a c id g iv e s th e h y d r a te o f t h e a c id , w hich i s s t a b l e below 55° a t 8 mm (U7) •

When e t h y l d ,& ,y ,y - t e t r a f l u o r o a c e t o a c e t a t e i s t r e a t e d

w ith 10# s u l f u r i c a c id , th e h y d r o ly s is i s co m p lete w ith in a few h o u r s .

16

The r a t e can b e fo llo w e d ro u g h ly by th e r a t e o f fo rm a tio n o f e t h y l a l c o h o l . Of i n t e r e s t i s th e f a c t t h a t more th a n 100# o f th e t h e o r e t i c a l amount o f e th a n o l can be re c o v e re d from th e h y d r o ly s is o f th e c ru d e e s t e r .

T h is i s

b e lie v e d t o be due to v a r i a b l e q u a n t i t i e s o f th e e th y l h e m ik e ta l i n th e cru d e e s t e r . w ith b e n z e n e .

The a c id a s p r e p a re d was d r ie d by a z e o tr o p ic d i s t i l l a t i o n I t i s a w a te r - s o lu b le , v e ry h y g ro sc o p ic s o l i d w hich, u n ­

l e s s p r o te c t e d from m o is tu re , d is s o lv e s i n th e w a te r i t a b s o rb s .

A

n e u t r a l e q u iv a le n t o f th e f r e s h l y p re p a re d anhydrous a d d a g re e d w ith th e t h e o r e t i c a l v a lu e v e ry c l o s e ly , b u t a f t e r s ta n d in g som etim e i n a c o r k -s to p p e re d b o t t l e , th e s o l i d d is s o lv e d i n th e a b so rb e d w a te r , and r e c r y s t a l l i z a t i o n from a b e n z e n e -e th e r s o lu t i o n gave th e m onohydrate. A ttem p ts to p re p a re d e r i v a t iv e s o f th e a c id ( p - n itr o b e n z y l e s t e r and 5 -b e n z y lth iu ro n iu rn s a l t ) o r o f th e k e to group ( 2 , U -d in itro p h e n y lh y d ra ­ zone) w ere u n s u c c e s s f u l. P r e p a r a tio n o f 1 , 1 , 3 , 3 - T e tr a f lu o r o a c e to n e .

The d e c a rb o x y l­

a t i o n o f / S - k e t o a c id s h as been th e s u b je c t o f numerous p a p e r s . a c c e p te d mechanism i s as fo llo w s :

The

H

Thus i t i s s e e n t h a t th e d e c a r b o x y la tio n p ro c e e d s th ro u g h th e e n o la te io n .

From t h i s one can p r e d i c t t h a t th e more n e g a tiv e t h e a lp h a s u b -

s t i t u t i e n t s t h e more r a p id th e r a t e o f d e c a r b o x y la tio n , s in c e th e more n e g a tiv e th e g ro u p s on th e o t-c a rb o n , th e c l o s e r th e e l e c t r o n p a i r

17

s h a re d by th e « .- c a r b o n and th e c a rb o x y l c a rb o n i s h e ld to t h e

-c a rb e n ;

and hen ce th e e a s i e r i t i s to r u p tu r e th e bond by s im u lta n e o u s s h i f t o f th e e l e c t r o n s on th e oxygen.

However, w ith

a c e t i c a c id a n o th e r f a c t o r i s p r e s e n t . o f sodium e th o x id e t o remove th e

te tra flu o ro a c e to -

As shown th ro u g h th e i n a b i l i t y

-h y d ro g en i n e th y l d i f l u o r o a c e t a t e ,

th e h y d ro g e n -ca rb o n bond i s v e r y s tr o n g on a carb o n c o n ta in in g two f lu o r in e - c a r b o n bonds i n s p i t e o f th e n e g a t i v i t y o f th e f l u o r i n e .

Spec­

t r o s c o p ic e v id e n c e i n d i c a t e s t h a t th e two f lu o r in e - c a r b o n bonds p e r m it v e r y l i t t l e p o l a r i z a t i o n o f th e e l e c t r o n s s u rro u n d in g t h e c a rb o n atom , and h ence do n o t a llo w e a sy fo rm a tio n o f a r e a c t i v e in t e r m e d ia te e n a b lin g rem oval o f th e hydrogen t o o c c u r ( 1 2 ) .

C o n seq u en tly , s in c e th e e n o la te

io n p o s tu l a t e d as th e in te r m e d ia te i n th e s e d e c a r b o x y la tio n s can be form ed o n ly w ith d i f f i c u l t y , i t was e x p e c te d t h a t d e c a r b o x y la tio n o f oL, e r ,> ,> - t e t r a f l u o r o a c e t o a c e t i c a c id would be d i f f i c u l t .

As e x p e c te d ,

th e s ta n d a r d c le a v a g e w ith d i l u t e a c id was u n s u c c e s s f u l.

P e d e rse n (3U)

s t a t e s t h a t th e c le a v a g e o f

- k e to a c id s i s c a ta ly z e d by p rim a ry

am in es; c o n s e q u e n tly an a n i l i n e s u l f a t e - s u l f u r i c a c id c le a v a g e was a tte m p te d , b u t w ith o u t a p p a re n t s u c c e s s .

Hudson (20) h a s u se d a c e t i c

a c id - h y d r io d ic a c id s o lu t i o n s f o r th e d e c a r b o x y la tio n o f d i f f i c u l t l y c le a v e d a c i d s ; t h i s was t r i e d w ith o u t s u c c e s s .

F i n a l l y , th e c le a v a g e

was acco m p lish ed w ith t h e u s e o f c o n s ta n t- b o i lin g h y d r o c h lo ric a c id . The p ro d u c t i s o l a t e d , how ever, i s n o t th e e x p e c te d 1 , 1 , 3 , 3 t e t r a f l u o r o a c e t o n e , b u t i n s t e a d i s a h ig h - b o ilin g m a t e r ia l w hich c r y s t a l l i z e s i n t o p l a t e l e t s on c o o lin g . o f 1 ,1 ,3 ,3 -te tra flu o ro a c e to n e .

T h is compound i s th e h y d ra te

S im ila r h y d r a te fo rm a tio n h a s been r e ­

p o r te d f o r h e x a f lu o ro a c e ty la c e to n e ( d ih y d r a te ) ( 3 8 ) , and 1 , 1 , 1 , 5 , 5 , 5 h e x a flu o ro -2 -p e n ta n o n e ( 2 6 ) .

The h y d r a te i s w a te r - s o lu b le , e t h e r -

18

s o lu b l e , and m o d e ra te ly s o lu b le i n b en zen e, from n h ic h i t can be r e c r y s ­ ta lliz e d .

(C a u tio n , an a z e o tro p e i s form ed, b»p. 7U-6 )

IVhen th e hy­

d r a t e was added to s u l f u r i c a c id and th e s o l u t i o n h e a te d , 1 , 1 , 3 , 3 te t r a f l u o r o a c e t o n e was o b ta in e d .

T h is i s a v o l a t i l e l i q u i d , b . p . 5 7 .6 ° ,

and d i s t i l l s from th e s u l f u r i c a c id i n a n e a r ly p u re s t a t e , s in c e upon r e c t i f i c a t i o n o f th e d i s t i l l a t e a l l o f th e l i q u i d d i s t i l l e d w ith in a tw o -d e g re e ra n g e .

1 , 1 , 3 , 3 - T e tr a f lu o r o a c e to n e r e a c t s i n s t a n t l y and v i g o r ­

o u s ly w ith w a te r o r e th a n o l, more l i k e an a c id h a lid e th a n a k e to n e , b u t g iv e s n e g a tiv e t e s t s f o r s o lu b le f lu o r i d e o r c h lo r id e i o n .

I t does n o t

g iv e a p o s i t i v e t e s t w ith 2 , b - d in itr o p h e n y lh y d r a z in e , n o r does i t r e a d ­ i l y form t h e sem ica rb a zo n e . The b o i l i n g p o in t o f 1 , 1 , 3 , 3 - te tr a f l u o r o a c e t o n e i s w o rth y o f n o te .

W ith th e v a r io u s o th e r f l u o r i n a t e d k e to n e s w hich have been p r e ­

p a r e d , a d e f i n i t e g e n e ra l tr e n d i n b o i l i n g p o in t w ith in c r e a s e d f l u o r i n e c o n te n t i s n o t i c e a b l e .

A cetone b o i l s a t 5 6 °; m o n o flu o ro aceto n e b o i l s a t

72° (7 8 ° ) ( 1 0 ,3 5 ) ; 1 ,1 - d if lu o r o a c e to n e , 1*6.5° ( 1 1 ) ; 1 , 1 , 1 - t r i f l u o r o a c e to n e , 2 1 .9 ° (1*7) ; and h e x a flu o ro a c e to n e , -2 8 ° (!!*)• u s u a l tr e n d o f th e f lu o r i n a t e d a c id s :

T h is i s a ls o th e

e le v a tio n o f th e b o i l i n g p o in t

w ith th e f i r s t f l u o r i n e atom , fo llo w e d by s u c c e s s iv e lo w e rin g w ith each f o llo w in g f l u o r i n e atom and a l a r g e d ro p i n b o ili n g p o in t w ith th e p e r f lu o r o compound.

T hus, one would n o t p r e d i c t 5 7 -6 ° f o r th e b o i l i n g

p o in t o f 1 , 1 ,3 ,3 -te tra flu o ro a c e to n e .

T his u n u s u a l b o i l i n g p o i n t i s no

d ou b t due t o th e s tr o n g hydrogen bonding in d u c e d by th e v e iy n e g a tiv e sy m m e tric a l g roups o f th e m o le c u le . R e a c tio n o f E th y l o i,o * ,> ,> -T e tr a f lu o r o a c e to a c e ta te w ith Anhydrous Ammonia.

S w arts (1*7) found t h a t e th y l

> , > ,> - tiif lu o r o -

a c e t o a c e t a t e r e a c t s w ith anhydrous ammonia to y i e l d two p r o d u c ts .

19

( I ) and ( I I ) .

CF^-G-CH2-CO-NH2 NH

CF3~ÇfCO~CO~OC2H5 NH

II

I V a rio u s o th e r

- k e to e s t e r s have r e a c te d w ith ammonia to form th e in lin e .

However, when e th y l e t,f lU ,> ,> - te tr a f lu o r o a c e ta te was r e a c te d w ith ammonia i n anhydrous e t h e r , n e i t h e r o f t h e two u s u a l p ro d u c ts n o r th e am ide was is o la te d .

I n s te a d , a w a te r - s o lu b le , e t h e r - s o l u b l e , w h ite s o l i d was

form ed f o r w hich a s t r u c t u r e c an n o t be c a l c u l a t e d .

The a n a l y t i c a l d a ta

and th e m o le c u la r w eig h t a g re e v e ry c l o s e l y w ith th e e m p ir ic a l fo rm u la C^H^F^NgO^.

A m i c r o - t e s t i n d i c a t e d th e p re s e n c e o f th e f r e e ammonium

io n , and i t i s s tr o n g ly s u s p e c te d t h a t th e compound c o n ta in s an ammon­ ium c h e l a t e , s in c e S w arts was a b le t o p r e p a r e th e ammonium c h e l a t e o f e th y l > , > ,> - t r i f l u o r o a c e t o a c e t a t e . P r e p a r a tio n o f E th y l l-C a r b e th o x y - 2 - e th o x y - l,1 ,3 $ 3 - t e t r a f lu o r o - 2 - p r o p y l C a rb o n a te .

I n th e a tte m p t t o condense e t h y l d i f l u o r o ­

a c e t a t e w ith e t h y l c h lo ro c a rb o n a te a compound was i s o l a t e d f o r w hich th e a n a l y s is and e m p iric a l fo rm u la a g re e d w ith t h a t o f e th y l l- c a r b e t h o x y - 2 e th o x y -1 , 1 , 3 , 3 - t e t r a f lu o r o - 2 - p r o p y l c a r b o n a te .

I n an a tte m p t t o p ro v e

th e s t r u c t u r e o f t h i s compound ( d e t a i l e d d is c u s s io n i s g iv e n l a t e r i n th e t h e s i s ) , e t h y l

« t,a t,V ,> - te tr a f lu o r o a c e to a c e ta te was r e a c te d w ith an

e t h e r e a l s o l u t i o n o f sodium e th o x id e to form th e sodium s a l t o f th e h e m ik e ta l, w hich was th e n r e a c te d w ith e t h y l c h lo ro c a rb o n a te .

The r e ­

a c t i o n p ro d u c t i s th e same as t h a t o b ta in e d i n th e p r e v io u s i n v e s t i ­ g a tio n s w ith sodium h y d r id e .

The r e a c t i o n was c a r r i e d o u t on a sem i­

m icro s c a l e s in c e th e s o le p u rp o se o f th e r e a c t i o n was t o p ro v e t h a t th e p o s tu l a t e d compound c o u ld be form ed th ro u g h th e g iv e n m echanism .

Conse­

q u e n tly , w h ile th e y i e l d i s n o t h ig h n o r th e compound s t r i c t l y p u re .

20

t h e r e i s no d o u b t t h a t t h i s i s th e same compound.

The v ig o r o f t h e r e ­

a c t i o n once a g a in i n d i c a t e s t h e ex trem e ten d e n c y o f th e k e to group i n t h i s / 9 - k e t o e s t e r t o h y d r a te o r form th e h e m ik e ta l ( a l c o h o l a t e ) ♦ P r e p a r a tio n o f 2 ,2 ,1 * ,U - T e tr a f lu o r o - 1 . 3 - b u ta n e d io l.

E th y l

* o i> > > y - te tra flu o ro a c e to a c e ta te was s u c c e s s f u lly red u ced w ith li t h i u m aluminum h y d rid e t o g iv e 2 »2 , U ,U ~ te tr a f lu o r o - l> 3 - b u ta n e d io l.

T h is g ly c o l

i s an o d o r le s s , c l e a r , s ir u p y l i q u i d a t room te m p e ra tu re s and form s a g la s s upon c o o lin g i n Dry I c e .

I n t h i s i t d i f f e r s from v a r io u s o th e r

f lu o r i n e - c o n t a i n i n g g ly c o ls p r e p a re d r e c e n t l y i n t h i s la b o r a t o r y (2 5 )The d i f f e r e n c e may be due t o th e u n sy m m etrical s u b s t i t u t i o n o f th e f l u o r i n e ato m s.

I t i s e t h e r - s o l u b l e a s w e ll a s w a te r - s o lu b le , b u t

s e p a r a t e s from c o ld b e n ze n e.

The p r e p a r a tio n by s ta n d a r d m ethods (30)

was fo llo w e d w ith th e e x c e p tio n t h a t th e e t h e r s o lu t i o n o f l i t h i u m alum­ inum h y d r id e m ust be i c e - c o l d a t th e s t a r t o f th e r e a c t i o n ; o th e rw is e th e r e a c t i o n i s to o v ig o ro u s and le a d s t o m inor e x p lo s io n s w ith c h a r r in g . Clemmensen R ed u c tio n o f E th y l The Clemmensen r e d u c tio n o f e t h y l

o L jd i> > » > -T e tra flu o ro a c e to a c e ta te .

«, > - t e t r a f l u o r o a c e t o a c e t a t e was

a tte m p te d i n o r d e r t o p r e p a r e 2 ,2 ,U > U - te tr a f lu o r o b u tr y ic a c i d .

A su rv e y

o f t h e l i t e r a t u r e r e v e a le d t h a t c e r t a i n /3 - k e to e s t e r s have been s u c c e s s ­ f u l l y red u ced by t h i s method when a tw o-phase sy stem i s u s e d t o p r e v e n t fo rm a tio n o f i n s o l u b l e p o ly m e ric z in c - o r g a n ic com plexes ( 2 8 ) .

For t h i s

r e a s o n , to lu e n e was u s e d a s t h e s o lv e n t, b u t none o f th e d e s ir e d p r o ­ d u c t c o u ld be i s o l a t e d .

I n s t e a d , t r a c e s o f 1 ,1 - d if lu o r o a c e to n e ( id e n ­

t i f i e d a s th e 2 , U -d in itro p h e n y lh y d ra z o n e ) and an i n s o l u b l e , i n f u s i b l e z in c s a l t w ere fo u n d .

I t i s p ro b a b le t h a t th e r e d u c tio n c o n d itio n s

removed f l u o r i n e from t h e m o lec u le and a t th e same tim e gave some

21

r e d u c tiv e c le a v a g e t o 1 , 1- d if l u o r o a c e to n e , s in c e i t i s known t h a t t h i s r e a c t i o n o f te n rem oves oc — h a lo g e n atoms (7 ) • a c t i o n w ith o u t to lu e n e gave th e same r e s u l t s •

A r e p e t i t i o n o f th e r e ­ I n b o th e x p e rim e n ts > th e

r e a c t i o n f l a s k was s e v e r ly e tc h e d . E x p e rim e n ta l P r e p a r a tio n o f ot

.V - T e t r a f l u o r o a c e t o a c e t i c A c id .

f l a s k was ch arg ed w ith 72 g . (O .U l m ole) o f e th y l a e e t o a c e t a t e and 50 m l. o f 10# s u l f u r i c a c id .

A 2 0 0 -m l.

te tra flu o ro -

The f l a s k was c o n n e c te d

to a 2- f o o t , c o n tin u o u s g l a s s s p ir a l- p a c k e d column eq u ip p ed w ith a v a r i ­ a b le t a k e - o f f h ead and c o n d e n se r.

The s o lu tio n was r e f l u x e d , and th e

t a k e - o f f was r e g u la te d so t h a t th e te m p e ra tu re o f th e v a p o r was k e p t a t 7 8 °.

A t o t a l o f 1 8 .2 g . (106# o f th e o ry ) o f 95# e th a n o l was s e p a r a te d

i n t h i s manner i n two h o u rs .

The s o lu t i o n was c o o le d and e t h e r -

e x t r a c t e d t o c o n s ta n t w e ig h t.

The e t h e r s o lu t i o n was d r ie d w ith sodium

s u l f a t e , fo llo w e d by D r i e r i t e , and f i n a l l y a z e o tr o p ic d i s t i l l a t i o n w ith benzene.

The s o l u t i o n was th e n r e c t i f i e d t o 7 0 °/8 mm., and th e p o t

r e s id u e d i s t i l l e d a t 3 mm.

A r e p e a te d vacuum d i s t i l l a t i o n gave 2 8 .U g .

o f a c l e a r l i q u i d , b .p . 720/2mm., w hich slo w ly s o l i d i f i e d a t room tem p er­ a t u r e t o e x tre m e ly h y g ro sc o p ic c r y s t a l s .

T h is i s a y i e l d o f U6#.

A

n e u t r a l e q u iv a le n t ta k e n on a sam ple p u r i f i e d by r e p e a te d f r a c t i o n a l d i s ­ t i l l a t i o n gave t h e fo llo w in g r e s u l t s : Found: 17k*3, 17k*0 .

C a lc d . f o r

17U .0.

The a c i d r e a d i l y form s th e h y d r a te w hich can be

r e c r y s t a l l i z e d from a b e n z e n e -e th e r s o lu t i o n , m .p. k 3 - 5 ° • A n a l. C a lc d . f o r

C, 25*00; H, 2 .0 8 .

Found: C, 25*01;

H, 2 .0 8 . P r e p a r a tio n o f 1 , 1 , 3 , 3 - T e tr a f lu o r o a c e to n e .

T h ir ty grams

22

(0 .1 5 m ole) o f e th y l

ol>a , > , > - t e t r a f l u o r o a c e t o a c e t a t e

and 50 m l. o f

c o n s ta n t —b o i l i n g h y d r o c h lo ric a c id were p la c e d i n a 125—ml * f l a s k s u r ­ m ounted by a c o n tin u o u s g la s s s p i r a l —packed r e f l u x c o n d e n se r s e t a t a te m p e ra tu re o f 5 0 ° .

Any uncondensed g a se s w ere l e d th ro u g h a w a te r -

c o o le d c o n d en ser and t r a p t o a Dry I c e t r a p .

The s o lu t i o n was r e f lu x e d

f o r f o r t y - e i g h t h o u rs d u rin g w hich tim e 10 m l. o f l i q u i d was cau g h t i n th e Dry I c e t r a p and 3 m l. o f l i q u i d i n th e w a te r -c o o le d t r a p .

The

l i q u i d i n th e Dry I c e t r a p was r e c t i f i e d t o y i e l d 6 .9 g . o f e th y l c h l o r i d e , b . p . 12° (68/5 o f t h e o r y ) .

The r e s id u e from th e r e c t i f i c a t i o n

and th e l i q u i d i n t h e w a te r-c o o le d t r a p b o th gave p o s i t i v e k e to n e t e s t s w ith 2 , b - d in itr o p h e n y lh y d ra z in e s o lu t i o n , and had an o d o r v e ry s i m i l a r t o 1 ,1 - d i f lu o r o a c e t o n e .

W ithout s e p a r a tio n , th e 2 , U - d in itr o p h e n y l-

h y d r a zone was p r e p a re d and gave ©range c r y s t a l s , m .p. 152° •

T h is i s

th e same compound i s o l a t e d i n s e v e r a l o th e r a tte m p te d d e c a r b o x y la tio n s . The a n a l y s i s shows t h i s k e to n e to be 1 ,1 - d if lu o r o a c e to n e a s th e o d o r s u g g e s te d .

The p re s e n c e o f t h i s k e to n e i n sm a ll q u a n t i t i e s can n o t be

e x p la in e d . A n a l. C a lc d . f o r

20.U5> Found: N, 2 0 .5 8 .

The aqueous s o l u t i o n i n th e f l a s k was e x tr a c te d c o n tin u o u s ly w ith e t h e r fo r th ir ty - s ix h o u rs.

The e t h e r e x t r a c t was d r ie d w ith sodium s u l f a t e

fo llo w e d by D r i e r i t e , and th e n th e e t h e r was removed by d i s t i l l a t i o n on a w a te r b a th th ro u g h a 1 2 -in c h ja c k e te d V ig reau x colum n. w eighed 22 g .

The r e s id u e

T h is was vacuum d i s t i l l e d th ro u g h th e V ig reau x column to

y i e l d 10 g . o f a l i q u i d , b . p . 1*6-7°/25 mm., w hich s o l i d i f i e d upon c o o l­ in g .

S u b lim a tio n o f a p o r ti o n o f th e c r y s t a l s gave th e s o l i d h y d r a te , o m .p . US • F iv e m i l l i l i t e r s o f th e cru d e h y d r a te was d i s t i l l e d from 5 m l.

23

o f c o n c e n tr a te d s u l f u r i c a c id t o g iv e *> m l. o f a c l e a r l i q u i d , b .p . 5>8°. R e c t i f i c a t i o n o f th e l i q u i d gave U g . o f 1 , 1 , 3 , 3 - te tr a f l u o r o a c e t o n e , b . p . 5 7 .6 ° , n^01 .3 0 2 5 . A n a l. C a lc d . f o r C^H.P^Og! C, 21».31*5 H, 2 .7 0 . 21».1 2 ; H, 2 .6 9 .

C a lc d . f o r C.HgF.O s C, 2 7 .7 1 ; H, 1.51».

Founds C, Founds C,

2 7 .5 8 ; H, 1 .5 7 . R e a c tio n o f E th y l o c .» q ,> ,> - T e tr a flu o r o a c e to a c e ta te w ith Anhydrous Ammonia.

Two grams o f e th y l

* ,c i,> >y - t e t r a f l u o r o a c e t o a c e t a t e

was d is s o lv e d i n $ g . o f anhydrous e t h e r , and a slow s tre a m o f ammonia was b u b b le d th ro u g h th e i c e - c o l d s o lu tio n f o r tw elv e h o u r s .

A c le a r

s o l u t i o n r e s u l t e d , b u t upon e v a p o ra tio n o f th e e t h e r l . $ 9 g . o f a w h ite s o l i d was form ed.

These c r y s t a l s w ere i n f i n i t e l y s o lu b le i n w a te r,

e th a n o l, and d io x a n e , m o d e ra te ly s o lu b le i n e t h e r , b u t in s o l u b l e i n benzene and p e tro le u m e t h e r .

S e v e ra l r e c r y s t a l l i z a t i o n s from b e n z e n e -

a lc o h o l s o lu t i o n s and b e n z e n e -e th y l a c e t a t e s o lu ti o n s gave c r y s t a l s m e ltin g a t 1 1 6 .5 -1 8 .^ ° w ith s u b lim a tio n .

A m ic r o - q u a l i t a t i v e t e s t (6 )

f o r th e p re s e n c e o f th e ammonium io n (5# c h l o r o p la ti n i c a c id ) gave im m e d ia te ly th e c h a r a c t e r i s t i c o c ta h e d ra o f ammonium c h l o r o p l a t i n a t e • No s tr o n g b a se was u s e d to g iv e h y d r o ly s is o f any amide b o n d s. A n a l. C a lc d . f o r C ^ H y F ^ O ^ : C, 2 5 .5 k ; H, 3 .0 0 ; N, 1 1 .9 1 ; m ol. w t . , 23f>.

Found: C, 2 5 .6 1 ; H, 2 .9 3 ; N, 12*05; m ol. w t ., 231.

P r e p a r a tio n o f E th y l l-C a r b e th o x y -2 - e th o x y -l$ 1 * 3 ,3 - t e t r a f lu o r o - 2 - p r o p y l C a rb o n a te .

A 50-m l. f l a s k surm ounted by a r e f l u x con­

d e n s e r was ch a rg e d w ith 25 m l. o f anhydrous e t h e r and 0 .5 7 g* (0 .0 2 5 m ole) o f pow dered sodium . m ole) o f e t h a n o l .

To t h i s s o l u t i o n was added 1.U3 m l. (0 .0 2 5

A f te r a l l th e sodium had r e a c t e d , 5 g . (0 .0 2 5 mole)

2U

o f e t h y l a . ,« t,> ,> - t e t r a f lu o r o a c e t o a c e t a t e was ad d ed . re s u lte d .

A v ig o ro u s r e a c t i o n

The s o l u t i o n was r e f lu x e d f o r one h o u r, and th e n 2 .6 9 6* (0 .0 2 5

m ole) o f e t h y l c h lo ro c a rb o n a te was ad d ed .

The r e f l u x i n g was c o n tin u e d

f o r an a d d i t i o n a l f o u r h o u rs , and th e n th e s o lu t i o n was l e f t t o s i t o v e r ­ n ig h t.

The sodium c h lo r id e was removed by f i l t r a t i o n , and th e s o lu t i o n

was r e c t i f i e d on a 12- in c h c o n c e n tr ic - tu b e column r a t e d a t 9 t h e o r e t i c a l p l a t e s t o g iv e 1 .0 2 g . o f e th y l l - c a r b e t h o x y - 2 - e th o x y - l ,1 ,3 ,3 - t e t r a f l u o r o 2 - p ro p y l c a r b o n a te , b . p . 9 6 ° / l mm., Qq^ I . 3935.

(The p u r i f i e d compound

a s p r e p a re d i n p a r t I I o f t h i s t h e s i s h as b .p . 9 8 ° / l mm., n ^ l . 3 9 W . ) P r e p a r a t i o n o f 2 ,2 >li>U - T e tr a f lu o r o - l,3 - b u ta n e d io l .

A s o lu t i o n

o f 6 .5 8 g . ( 0 .2 m ole) o f l i t h i u m aluminum h y d rid e d is s o lv e d i n 150 m l. o f anhydrous e t h e r was p re p a re d i n a 5 00-m l. , 3 -n eck ed f l a s k eq u ip p ed w ith s e a le d s t i r r e r , d ro p p in g f u n n e l, and r e f l u x c o n d e n se r s to p p e re d w ith a c a lc iu m c h lo r id e d ry in g tu b e .

A f te r th e s o lu t i o n was r e f l u x e d

f o r two h o u rs th e f l a s k was im m ersed i n i c e , and a s o lu t i o n o f 25 g* (0.12ij. m ole) o f e th y l w l,o t> > > > -te tra flu o ro a c e to a c e ta te d is s o lv e d i n 50 m l. o f anhydrous e t h e r was added d ropw ise t o th e c o n te n ts Ten m in u tes a f t e r t h i s

o f th e f l a s k .

a d d itio n , w a te r was added dropw ise u n t i l th e

e x c e s s l i t h i u m aluminum h y d rid e had r e a c te d .

Two hundred and f o r t y - s i x

grams o f 20% s u l f u r i c a c id was th e n added, and th e s o l u t i o n was r e ­ f lu x e d f o r two h o u rs .

The e t h e r l a y e r was

s e p a r a te d from th e aqueous

l a y e r , and th e aqueous l a y e r was e x tr a c t e d c o n tin u o u s ly w ith e t h e r f o r tw e lv e h o u r s .

The e t h e r e x t r a c t s w ere d r ie d w ith sodium s u l f a t e , and

100 m l. o f benzene was added t o th e s o lu t i o n .

The s o l u t i o n was th e n

r e c t i f i e d u n t i l th e te m p e ra tu re re a c h e d 8 0 °.

The homogeneous s o lu t i o n

re m a in in g i n th e p o t s e p a r a te d i n t o two l a y e r s upon c o o lin g .

The c ru d e

2$

2»2 > U ,U - te tr a f lu o r o - l,3 - b u ta n e d io l w eighed 1 3 .6 g .

D i s t i l l a t i o n th ro u g h

a 1 2 -in c h ja c k e te d V ig reau x column gave 10*2 g* o f c l e a r , s ir u p y l i q u i d , b . p . 8 0 - l ° / 2 mm., n ^ ° 1 .3 0 0 0 .

T h is i s a $0.7% y i e l d .

The c e n t r a l f r a c ­

t i o n was r e d i s t i l l e d , and th e c e n t r a l f r a c t i o n o f t h i s d i s t i l l a t e a n a l­ yzed. A n al. C a lc d . f o r

: C, 29.61*; H, 3 .7 3 .

Found: C,

2 9 .6 ; H, 3«72. The p - n i tro b e n z o a t e was p re p a re d by s ta n d a rd m ethods, m .p. 9$° •

In r e ­

c r y s t a l l i z a t i o n s from e th a n o l, th e e s t e r s e p a r a te s a s an o i l u n le s s d i l u t e s o l u t i o n s a r e allo w ed t o c r y s t a l l i z e s lo w ly . A n a l. C a lc d . f o r

N, 1 0 .0 8 .

Clemmensen R e d u c tio n o f E th y l a

Found: N, 1 0 .1 0 .

«> - T e tr a iT u o r oac e to a c e t a t e .

F o r ty gram s o f am algam ated z in c was p r e p a re d by p la c in g 1*0 g » o f mossy z in c i n a $ 00 -m l. f l a s k and a d d in g i n th e o r d e r named $0 m l. o f w a te r , 3 g . o f m e rc u ric c h l o r id e , and 2 m l. o f c o n c e n tr a te d h y d r o c h lo ric a c id . The m ix tu re was shaken f o r f i v e m in u te s, a f t e r w hich th e aqueous s o lu ­ t i o n was d e c a n te d and r e p la c e d by 2$ m l. o f w a te r, $8 m l. o f c o n c e n tr a te d h y d r o c h lo r ic a c id , 33 m l. o f to lu e n e , and 2 1 .$ g . ( 0 .1 6 mole) o f e th y l a

, e t ,> ,'y - t e t r a f l u e r o a c e t o a c e t a t e .

The m ix tu re was r e f lu x e d v ig o r o u s ly

f o r tw e n ty h o u rs w ith th e a d d itio n o f 17 m l. o f c o n c e n tr a te d h y d r o c h lo r ic a c i d e v e ry s i x h o u r s .

A rrangem ents were made to c o l l e c t any ev o lv ed

g a se s i n a Dry I c e - t r i c h l o r o e t h y l e n e t r a p .

At th e end o f t h i s p e r io d

ab o u t 2 ml* o f l i q u i d p r e s e n t i n th e Dry I c e t r a p gave a p o s i t i v e t e s t w ith 2 , h - d in itr o p h e n y lh y d ra z in e and had th e c h a r a c t e r i s t i c o d o r o f 1 , 1 d if lu o r o a c e to n e • The r e a c t i o n m ix tu re was n e u t r a l i z e d w ith p o ta s s iu m c a r b o n a te , and th e to lu e n e and a lc o h o l removed by steam d i s t i l l a t i o n to p re v e n t

26

fo rm a tio n o f e t h y l 1 , 1 ,3 >3 - t e t r a f l u o r o b u t y r a t e .

The o rg a n ic l a y e r o f

th e d i s t i l l a t e was w a te r - e x tr a c te d , and th e com bined w a te r e x t r a c t s added to th e o r ig in a l s o lu tio n .

The s o lu t i o n was th e n made s tr o n g l y a c id ic

w ith $0 m l. o f c o n c e n tr a te d s u l f u r i c a d d and c o n tin u o u s ly e x tr a c t e d w ith e th e r fo r f o r ty - e ig h t h o u rs.

D i s t i l l a t i o n o f th e d r ie d e t h e r e x t r a c t

gav e o n ly t r a c e s o f a l i q u i d , b . p . 5>0°/50 mm., w hich s o l i d i f i e d on c o o l­ in g .

A heavy w h ite p r e c i p i t a t e p r e s e n t i n th e aqueous l a y e r was removed

by f i l t r a t i o n .

A p o r ti o n o f t h e s o l i d d is s o lv e d i n w a te r was t r e a t e d

w ith h ydrogen s u l f i d e , and gave th e c h a r a c t e r i s t i c w h ite p r e c i p i t a t e o f z in c s u l f i d e .

The s o l i d i s in s o lu b l e i n c o n c e n tr a te d s u l f u r i c a c id ,

b u t r e a c t s w ith h o t c o n c e n tr a te d s u l f u r i c a c id to l i b e r a t e an a c id ic gas which r e a c t s w ith w a te r to form an a c i d ic s o lu t i o n w ith sim u lta n e o u s p r e c i p i t a t i o n o f a w h ite s o l i d .

The o r i g i n a l s o l i d i s b e lie v e d t o be

z in c f l u o s i l i c a t e , s in c e th e p re s e n c e o f f l u o s i l i c i c a c id i s a t t e s t e d t o by th e s e v e re e tc h in g o f th e r e a c t i o n f l a s k . The r e a c t i o n was r e p e a te d w ith o u t u s e o f to lu e n e as s o lv e n t. Once, a g a in , v e ry n o tic e a b le q u a n t i t i e s o f 1 ,1 - d if lu o r o a c e to n e w ere form ed, and s e v e re e tc h in g o f th e g la s s equipm ent to o k p la c e a lth o u g h r e f l u x i n g was s to p p e d a f t e r e ig h t h o u r s .

The r e a c t i o n m ix tu re was

e t h e r - e x t r a c t e d , b u t no 2 ,2 ,U > U " te tra f lu o ro b u ty r ic a c id c o u ld be i s o l ­ a te d from th e d r ie d e x t r a c t . Summary E th y l D if lu o r o a c e ta te h as b een s u c c e s s f u ll y s e lf - c o n d e n s e d by means o f sodium h y d rid e to y i e l d th e c o rre s p o n d in g /^ - k e to e s t e r , e th y l ct ^ % ,y ,> - te tr a f lu o r o a c e tG a c e ta te , and a s tu d y h a s b een made o f

27

i t s p ro p e rtie s . to y ie ld

E th y l * >*>>»> - t e t r a f l u e r o a c e t o a c e t a t e h a s been h y d ro ly z e d

,V - t e t r a f l u o r o a c e t o a c e t i c a c id and i t s m onohydrate»

C leav ­

age o f t h i s a c id h a s b een accom plished* w ith th e p r e p a r a t io n o f 1 ,1 ,3 * 3 t e t r a f l u o r o a c e t o n e and i t s h y d r a te .

A ll t h r e e o f th e s e compounds d i s p l a y

v e r y u n u s u a l p r o p e r t i e s w hich a r e d is c u s s e d i n d e t a i l . E th y l c < - t e t r a f l u e r o a c e t o a c e t a t e h as b een re d u c e d to 2 , 2 , U » U - te tr a f lu o r o - l,3 - b u ta n e d io l by means o f l i t h i u m aluminum h y d r id e , and th e p - n itr o b e n z o a te p r e p a re d . V a rio u s o th e r r e a c t i o n s o f e th y l a c e t a t e have b een i n v e s t i g a t e d .

c t,«(,,>,>- t e t r a f l u o r o a c e t o -

P a rt H MIXED ESTER CONDENSATIONS OF ETHYL DIFLUOROACETATE

29

I n tr o d u c tio n A v e r y v a lu a b le s y n th e s is w ould b e added to f l u o r i n e c h e m is try i f e t h y l d i f l u o r o a c e t a t e c o u ld b e made t o condense a s th e e n o liz in g e s t e r i n m ixed a c e t o a c e t i c e s t e r c o n d e n s a tio n s , s in c e by t h i s m ethod an un­ l i m i t e d number o f compounds c o u ld be made w ith < t,c t- d iflu o r o g ro u p s , no g e n e r a l method b e in g known f o r t h i s p r o c e s s a t p r e s e n t .

The p u rp o se o f

t h i s r e s e a r c h , th e n , was t o condense e th y l d i f l u o r o a c e t a t e w ith a n o th e r e s t e r o r a c id c h lo r id e by th e u s e o f sodium h y d r id e .

I t i s w e ll e s ta b ­

l i s h e d t h a t a c e t o a c e t i c e s t e r c o n d e n s a tio n s a r e e q u ilib r iu m r e a c t i o n s , and as such i t i s e v id e n t t h a t o n ly e s t e r s n o t h a v in g an e a s i l y remov­ a b le

-h y d ro g en ( o r a c i d c h lo r id e s ) may b e u s e d i n th e m ixed conden­

s a t i o n s , s in c e th e e n o la te io n o f e th y l d i f l u o r o a c e t a t e i s i t s e l f a v e ry s tr o n g b a se and w i l l remove th e hydrogen from th e c o n ju g a te a d d o f any w eaker b a se - e t h y l a c e t a t e f o r in s t a n c e .

C o n seq u en tly , th e i n v e s t i ­

g a tio n s w ere c a r r i e d o u t w ith r e a c t i v e e s t e r s , su ch a s e t h y l c a r b o n a te , p h en y l t r i f lu o ro a c e t a t e , and e t h y l b e n z o a te , w hich have no o c -h y d ro g en . I n no c a s e was a m ixed c o n d e n s a tio n p ro d u c t i s o l a t e d .

However, th e r e ­

a c t i o n s w ith a c id c h lo r id e s do y i e l d p ro d u c ts o f t h e o r e t i c a l im p o rtan ce s in c e th e y in v o lv e a c y l a t i o n o f a h e m ik e ta l.

T h is l a t t e r r e a c t i o n i s

b e lie v e d t o o c c u r r a t h e r i n f r e q u e n t l y . C o n d en satio n s w ith A cid C h lo rid e s D is c u s s io n The o r i g i n a l p u rp o se o f t h i s i n v e s t i g a t i o n was to p r e p a r e e t h y l d iflu o r o m a lo n a te th ro u g h th e m ixed a c e t o a c e tic e s t e r c o n d e n s a tio n

30

o f e t h y l d i f l u o r o a c e t a t e and e t h y l c h lo ro c a rh o n a te i n th e p r e s e n c e o f sodium h y d r id e .

I t was o b v io u s t h a t d i f f i c u l t y would be e x p e rie n c e d i n

p r e p a r in g and i s o l a t i n g th e e n o la te io n o f e th y l d i f l u o r o a c e t a t e due t o th e r a p i d i t y o f i t s s e lf - c o n d e n s a tio n .

T h e re f o re , e a r l y a tte m p ts a t

t h i s c o n d e n s a tio n w ere made t o p roduce th e e n o la te io n i n th e p re s e n c e o f th e e t h y l c h lo r o c a r b o n a te .

However, i n e v e ry c a s e , r e g a r d l e s s o f

s o lv e n t u s e d , r e a c t i o n tim e , r a t e o f a d d itio n o f e t h y l d i f l u o r o a c e t a t e , e t c . , th e p rim a ry r e a c t i o n t o form th e e n o la te io n o f e t h y l d i f l u o r o ­ a c e t a t e d id n o t p ro c e e d i n th e p re s e n c e o f e th y l c h lo r o c a r b o n a te .

It

seems p ro b a b le t h a t t h i s i s due t o th e c o a tin g o f th e sodium h y d rid e p a r t i c l e s w ith in s o l u b l e sodium c h lo r id e .

T h is rem ain ed t r u e even when

g l a s s b ea d s w ere in tr o d u c e d i n t o th e s t i r r e d s o lu tio n to c ru sh th e sodium h y d rid e p a r t i c l e s .

An a tte m p t was th e n made t o form th e e n o la te io n

r a p i d l y by th e u s e o f e x c e ss sodium h y d rid e i n d io x an e fo llo w e d by a d d i­ t i o n o f e t h y l c h lo ro c a rb o n a te t o th e s o lu t i o n a t o n c e .

When t h i s was

done, a good y i e l d o f a h ig h - b o ilin g l i q u i d was o b ta in e d .

The b o i l i n g

p o i n t , m o le c u la r w e ig h t, and e le m e n ta l a n a ly s is d id n o t a g re e w ith t h a t p r e d i c t e d f o r e th y l d iflu o r o m a lo n a te , how ever. c l o s e l y w ith an e m p iric a l fo rm u la

Such a compound c o u ld

have one o f th e fo llo w in g s t r u c t u r e s . 0-C0-0CgH^ CHFo- e - C F o -C 0 -0 C oH*

2 i

2

I n s te a d th e y a g re e d

0C2% CHF -CO-CF -C-O-CO-OC H„

2 >

2

OC2H5

2 i

o c 2H5

I

ii

A s u i t a b l e mechanism can b e g iv e n f o r e i t h e r s t r u c t u r e . f i r s t th e fo rm a tio n o f e t h y l

2 5

cl,e t,> ,Y

T h is in v o lv e s

- te tr a f lu o r o a c e to a c e ta te th ro u g h

th e s e l f - c o n d e n s â t! on o f e th y l d i f l u o r o a c e t a t e .

T h is s te p i s s u p p o rte d

31

b y t h e f a c t t h a t i n a l l c a s e s n o t o v e r 0*5 e q u iv a le n t o f hydrogen was e v o lv e d a lth o u g h an e q u iv a le n t o f sodium h y d rid e was u s e d .

The r e a c t i o n

l i b e r a t e s th e e th o x id e io n , a m o d e ra te ly s tr o n g b a s e , w hich c o u ld th e n r e a c t w ith e i t h e r c a rb o n y l g roup t o form th e sodium s a l t o f th e hem ia c e t a l ( I I I ) o r ( IV ) . chf 2- c - c f 2- co - oc 2H£

chf 2- co- c f 2- c - oc 2H£

oc 2 h5

oc 2h^

iv

h i

A c tu a lly ( I I I ) i s th e p o s tu l a t e d i n te r m e d ia te i n th e a c c e p te d mechan­ ism f o r t h e a c e t o a c e t i c e s t e r c o n d e n s a tio n .

E i t h e r ( I H ) o r (IV ) c o u ld

th e n r e a c t w ith e t h y l c h lo r o c a rb o n a te t o g iv e ( I ) o r ( I I ) .

The f a c t

t h a t t h e sodium s a l t o f th e h e m ia c e ta l o f h ig h ly f lu o r i n a t e d c a rb o n y l compounds d oes form can be d e m o n stra te d by th e ex o th erm ic r e a c t i o n o f e t h y l t r i f l u o r o a c e t a t e o r e t h y l d i f l u o r o a c e t a t e w ith an e t h e r e a l s o lu ­ t i o n o f sodium e th o x id e (1 9 ) •

To p ro v e th e r e a c t i o n c o u ld go th ro u g h

th e p o s t u l a t e d m echanism , a q u a n tit y o f e t h y l a c e t a t e was p r e p a re d and i s o l a t e d .

o r ,o t,> ,'V - te tra f lu o ro a e e to -

T h is was th e n added to an e t h e r e a l

s o l u t i o n o f an e q u iv a le n t amount o f sodium e th o x id e .

A v ig o ro u s r e a c t i o n

to o k p l a c e , su p p o se d ly fo n n in g th e s a l t o f th e h e m ia c e ta l ( I I I ) o r ( IV ) . When t r e a t e d w ith an e q u iv a le n t amount o f e th y l c h lo r o c a rb o n a te , t h i s compound gave a s th e p ro d u c t ( I ) o r ( I I ) , i d e n t i f i e d by b o i l i n g p o in t and r e f r a c t i v e in d e x . th is th e s is .)

(E x p e rim e n ta l d e t a i l s a r e g iv e n i n p a r t I o f

Of th e two s t r u c t u r e s , ( I ) i s fa v o re d s in c e n o t o n ly i s

th e k e to group more l i k e l y to form a s t a b l e h e m ia c e ta l th a n th e e s t e r c a rb o n y l g ro u p , b u t i n a d d i t i o n i t i s d o u b ly a c t i v a t e d by th e f o u r f l u o r i n e a to m s.

As a f u r t h e r i n d i c a t i o n , how ever, e t h y l t r i f l u o r o -

32

a c e t a t e was r e a c te d w ith an e t h e r e a l s o lu t i o n o f sodium e th o x id e to g iv e th e sodium s a l t o f t h e h e m ia c e ta l (V ). CF3C02C2Hç + NaOCgHç --- ►

9 + CFj-C-OCgHg + Na 6 c 2h5 V

T h is (V) was th e n t r e a t e d w ith e t h y l c h lo r o c a rb o n a te , b u t an 88^ y i e l d o f e th y l c a rb o n a te was o b ta in e d and th e e th y l t r i f l u o r o a c e t a t e r e c o v e re d . Thus th e e th o x id e i o n and e th y l t r i f l u o r o a c e t a t e a r e i n e q u ilib r iu m w ith th e h e m ia c e ta l s a l t , and th e e th o x id e io n i s th e s tr o n g e r b a s e o f th e tw o .

T h e re fo re , i t seems l i k e l y t h a t ( I ) i s th e p r o p e r s t r u c t u r e s in c e

even w ith t h r e e f l u o r i n e atom s a d ja c e n t to th e e s t e r c a rb o n y l g ro u p , th e compound (V) i s n o t c a p a b le o f form in g a b a s e s tr o n g e r th a n th e e th o x id e io n . One o th e r p r e d ic te d p ro d u c t, d i e t h y l 2 , 2 , U» U - te tr a f lu o r o - 3 - o x e g l u t a r a t e , c o u ld be form ed th ro u g h th e fo llo w in g m echanism. 1.

C E F 2 COCF2 CO2 C2H^ ^ OCgH^

C F ^ C Q C F g C Q g C g E ^ 4* CgH^OH

2.

CFgCOCF^COgCgH^ 4* ClCOgCgH^ ""eCgH^OgC—CF^^CO^CFg—COgCgH^ 4* C l

T h is was t h e f i r s t compound t o be p o s tu la te d , b u t th e e le m e n ta l a n a ly s is does n o t c o n firm i t , n o r does t h e p r e p a r a tio n from e th y l e t,ot,> ,> - t e t r a f lu o r o a c e t o a c e t a t e w ith sodium e th o x id e and e th y l c h lo r o c a rb o n a te i n d i ­ c a t e i t , s in c e th e e th o x id e io n s h o u ld n o t remove th e > -h y d ro g e n u n d e r th e s e c o n d itio n s when i t i s n o t c a p a b le o f rem oving th e oc-hydrogen o f e th y l d iflu o r o a c e ta te .

R ep eated a n a ly s e s o f th e c a r e f u l l y r e p u r i f le d

p r o d u c t o f t h e c o n d e n s a tio n w ith e t h y l c h lo ro c a rb o n a te and e th y l d i ­ f l u o r o a c e t a t e gave th e same e m p ir ic a l fo rm u la .

As a n o th e r i n d i c a t i o n ,

th e r e a c t i o n was r e p e a te d u s in g b en zo y l c h lo r id e i n s t e a d o f e th y l

33

c h lo r o c a r b o n a te .

The r e s u l t i n g compound a n a ly z e d c o r r e c t l y f o r th e b en z o y l

e s t e r o f th e h e m ik e ta l and d o es n o t g iv e a t e s t f o r a k e to group w ith 2,1*d i n i tro p h e n y lh y d r a z i n e . As p r o o f o f s t r u c t u r e , how ever, th e c o n d e n s a tio n p r o d u c t was red u c e d w ith l i t h i u m aluminum h y d r id e .

The p r o d u c t o f th e r e d u c tio n was

2 ,2 ,1 * ,U - t e t r a f l u o r o - 1 , 3 - b u ta n e d io l, th e same g ly c o l o b ta in e d from th e s i m i l a r r e d u c tio n o f e th y l ci ,c ( ,> , > - t e t r a f l u o r o a c e t o a c e t a t e .

T h is g ly c o l

could, n o t have b e en d e r iv e d from d i e t h y l 2 ,2 , U, l * - t e t r a f lu o r o - 3 - o x o g l u t a r a t e b u t would be th e e x p e c te d p r o d u c t from th e r e d u c tio n o f e th y l 1 - c a r b e t h e x y - 2 - e t h o x y - l ,1 ,3 ,3 - t e t r a f lu o r o - 2 - p r o p y l c a r b o n a te •

T h is e v i ­

den ce, t o g e t h e r w ith th e p r o p e r t i e s o f e th y l oi >àL9>Jr - t e t r a f l u o r o a c e t o a c e t a t e a s p r e s e n te d i n p a r t I o f t h i s t h e s i s , c o n firm s th e p o s t u l a t e d s tr u c tu r e ( I ) . E x p e rim en tal P r e p a r a t i o n o f E th y l l- C a r b e th o x y - 2 - e th o x y - l,1 ,3 ,3 - t e t r a f l u o r o 2 -p ro p y l C a rb o n a te .

A 1 - l i t e r , 3 -necked f l a s k was f i t t e d w ith a d ro p p in g

f u n n e l, s e a le d s t i r r e r , and r e f l u x c o n d e n se r.

The system was p r o te c t e d

from m o is tu re by a c a lc iu m c h lo r id e tu b e , and p r o v is io n s were made to m easure e v o lv e d h y d ro g en .

Anhydrous d io x an e (300 g . ) was d i s t i l l e d from

sodium h y d rid e i n t o th e f l a s k , and 12 g . o f f in e ly - g r o u n d sodium h y d rid e (d ry -b o x ) was a d d ed .

The s t i r r e d s o lu t i o n was h e a te d to r e f l u x tem p era­

t u r e , and 62 g . o f e t h y l d i f l u o r o a c e t a t e was p la c e d i n t h e f u n n e l w ith a b o u t o n e - h a lf o f th e e s t e r b e in g added t o th e s o l u t i o n a t o n ce.

The

r e a c t i o n was i n i t i a t e d by th e a d d iti o n o f 2 m l. o f e th a n o l, and a f t e r a f i f t e e n m in u te i n d u c tio n p e r io d e v o lu tio n o f hydrogen became r a p i d .

The

3h

re m a in d e r o f t h e e s t e r was added slow ly» and when th e e v o lu tio n o f hydrogen slow ed ( f o r t y - f i v e m in u te s ) , 1 0 8 .5 g- o f e th y l c h lo r o c a rb o n a te was added a t a r a t e m a in ta in in g r e f l u x .

Hydrogen c e a se d t o ev o lv e i n

ene h o u r, a t o t a l o f 8 l i t e r s b e in g c o l l e c t e d .

The s o l u t i o n was r e ­

f lu x e d f o r an a d d i t i o n a l s i x h o u rs , th e n c o o le d , vacuum f i l t e r e d , and vacuum d i s t i l l e d .

R e c t i f i c a t i o n o f th e d i s t i l l a t e gave 35ȣ g . o f a

c o l o r l e s s l i q u i d , b . p . 9 8 . 5 ° / l mm., n^°1.39U 3. a c o n v e rs io n o f

b a s e d on e t h y l d i f l u o r o a c e t a t e .

A n a l. C a lc d . f o r Found: C,

T h is q u a n tity r e p r e s e n ts

C, L l .2 5 ; H, 5»0U; m ol. w t ., 320.

H, 5*16; m ol. w t ., 300. I n a r e p e t i t i o n o f t h i s c o n d e n s a tio n , 62 g . ( 0 .5 m ole) o f

e th y l d i f l u o r o a c e t a t e , 6 g . ( 0 .2 5 m ole) o f sodium h y d r id e , and 5U g* ( 0 .5 m ole) o f e t h y l c h lo r o c a rb o n a te were condensed w ith o u t u s in g a s o lv e n t .

S u f f i c i e n t tim e was a llo w ed to p e rm it th e s e lf - c o n d e n s a tio n

o f th e e t h y l d i f l u o r o a c e t a t e b e f o r e th e e th y l c h lo ro c a rb o n a te was ad d ed . By t h i s m ethod t h e y i e l d was i n c r e a s e d t o 60%, U7.8 g . o f e th y l 1 - c a r b e t h e x y - 2 - e t h o x y - l ,l , 3 ,3 - t e t r a f l u o r o - 2 - p r o p y l c a rb o n a te b e in g i s o l a t e d a s th e p r o d u c t. R ed u c tio n o f E th y l l- C a r b e th o x y - 2 - e th o x y - l,1 ,3 $ 3 - t e t r a f l u o r o 2 - p ro p y l C a rb o n a te .

A 1 - l i t e r , 3 -n eck ed f l a s k was eq u ip p ed w ith a s e a le d

s t i r r e r , d ro p p in g f u n n e l, and r e f l u x c o n d e n s e r.

A rrangem ents w ere made

t o co n d u c t any e v o lv e d hy d ro g en from th e v i c i n i t y o f th e e l e c t r i c m o to r, and th e sy stem was p r o te c t e d from m o is tu re by means e f a c a lc iu m c h lo r id e d r y in g tu b e .

T h ree h u n d red m i l l i l i t e r s o f anhydrous e t h e r was p la c e d i n

th e f l a s k , and 1 3 .5 g« (0 .3 5 5 m ole) o f pow dered lit h iu m aluminum h y d rid e was d is s o lv e d i n th e e t h e r .

A s o lu t io n o f Ijl g . (0 .1 3 m ole) o f

35

e t h y l l - c a r b e t h o x y - 2 - e t h o j t y - l ,l , 3 , 3- t e t r a f l u o r o - 2- p r o p y l c a r b o n a te d i s ­ s o lv e d i n 100 m l. o f an hydrous e t h e r was th e n d ropped slo w ly i n t o th e n itr o g e n - b la n k e te d m ix tu re .

A f t e r a d d i t i o n o f th e e s t e r , w a te r was

added d ro p w ise to th e i c e - c o l d s o lu t i o n u n t i l no more h y d ro g en was e v o lv e d .

The m ix tu re was th e n p o u re d s lo w ly i n t o 375 g- o f 20% s u l f u r i c

a c id and th e s o lu t i o n was allo w e d to s ta n d f o r two h o u r s .

The e t h e r

e x t r a c t was s e p a r a te d and th e aqueous l a y e r was e x t r a c te d c o n tin u o u s ly w ith e t h e r f o r t h i r t y - s i x h o u r s . w ith sodium s u l f a t e .

The combined e t h e r e x t r a c t s w ere d r ie d

The e t h e r was d i s t i l l e d to a volume o f 100 m l.,

and 100 m l. o f benzene was added t o th e s o l u t i o n .

The s o l u t i o n was th e n

r e c t i f i e d t o a te m p e ra tu re o f 8 0 °, th e p o t r e s id u e c o o le d , and th e an­ h y d ro u s lo w er l a y e r c o n ta in in g th e cru d e g ly c o l vacuum d i s t i l l e d th ro u g h a 1 2 -in c h ja c k e te d V ig reau x column t o y i e l d 1 3 «US g* (66%) o f 2 , 2 ,l i ,l i t e t r a f l u o r o - l , 3 - b u t a n e d i o l , b . p . 8 5 °/5 mm., n ^ l.3 6 0 5 *

The p - n i t r o ­

b e n z o a te was p re p a re d by s ta n d a rd m ethods, m .p . 95°• P r e p a r a tio n o f l-C a r b e th o x y - 2 - e th o x y - l»1 $3 , 3 - t e t r a f l u o r o - 2 p ro p y l B e n z o a te .

T h is r e a c t i o n was c a r r i e d o u t i n a manner s im i l a r t o

t h a t w ith e th y l c h lo r o c a rb o n a te .

I n th e f l a s k were p la c e d 2 0 1 .5 g . o f

anhydrous d io x a n e , 2 ^ .8 g . ( 0 .2 m ole) o f e th y l d i f l u o r o a c e t a t e , and g . ( 0 .2 m ole) o f sodium h y d r id e .

The s o lu t i o n was b ro u g h t t o r e f l u x ,

and a f t e r e v o lu tio n o f 2 l i t e r s o f h y d ro g en , 5 6 .2 g . (O .lt m ole) o f b e n z o y l c h l o r id e was dropped slo w ly i n t o th e s o l u t i o n .

E v o lu tio n e f

hyd ro g en c e a s e d when a b o u t o n e - h a lf o f th e b e n z o y l c h l o r id e h ad been added.

The re m a in d e r was dropped i n r a p i d l y , and th e s o l u t i o n a llo w e d

t o s ta n d f o r two h o u r s .

The s o lu tio n was th e n vacuum f i l t e r e d and

r e c t i f i e d u n d e r vacuum t o a te m p e ra tu re o f 6k6/ $ mm*

The p o t r e s id u e

36

s o l i d i f i e d on c o o lin g .

T h is was vacuum d i s t i l l e d to g iv e a 2 -p h a se d i s ­

t i l l a t e , w h ite s o l i d and c l e a r l i q u i d .

T h is m ix tu re was d is s o lv e d i n

e t h e r and w ashed w ith 1056 sodium c a r b o n a te u n t i l no more carb o n d io x id e was e v o lv e d .

Vacuum r e c t i f i c a t i o n gave 5 g . o f a c l e a r l i q u i d , b . p .

1 2 6 ° / l mm., n ^ ° l.U 5 9 2 .

The low y i e l d i s due to th e a d d iti o n o f th e

b e n z o y l c h l o r id e b e f o r e a l l t h e e th y l d i f l u o r o a c e t a t e had r e a c t e d . A n a l. C a lc d . f o r

C, 5 l* lU ; H, U»58.

Found: C,

51.U0; H, W 6 . C o n d e n sa tio n s w ith O th er E s te r s D is c u s s io n Many a tte m p ts w ere made t o condense e th y l d i f l u o r o a c e t a t e as th e e n o l i z in g e s t e r i n m ixed a c e t o a c e t i c e s t e r c o n d e n s a tio n s , b u t i n no c a s e was any p r o d u c t o t h e r th a n th e s e lf - c o n d e n s a tio n p ro d u c t i d e n t i f i e d . U s u a lly , a h ig h p o ly m er was fo u n d w hich c o u ld n o t be i d e n t i f i e d .

A ttem pts

w ere made t o condense e t h y l d i f l u o r o a c e t a t e w ith e th y l c a r b o n a te , e th y l o x a l a t e , e t h y l t r i f l u o r o a c e t a t e , p h en y l t r i f l u o r o a c e t a t e , and e th y l ben­ z o a te .

S o lv e n ts i n v e s t i g a t e d in c lu d e e t h e r , d ib u ty l e t h e r , d io x a n e , and

ex cess " a c y la tin g " e s te r .

Many d i f f e r e n t te c h n iq u e s w ere u s e d i n th e

a tte m p t t o p r e p a r e t h e e n o l a t e io n o f e th y l d i f l u o r o a c e t a t e i n th e p r e ­ s e n c e o f th e " a c y la tin g " e s t e r and th e ab sen ce o f e t h y l d i f l u o r o a c e t a t e b u t w ith o u t s u c c e s s .

The f a i l u r e o f th e mixed c o n d e n s a tio n to o c c u r

can b e a t t r i b u t e d t o two th i n g s :

th e r a p i d i t y w ith w hich th e e n o la te

i o n o f e t h y l d i f l u o r o a c e t a t e co n denses w ith any e th y l d i f lu o r o ac e t a t e p r e s e n t , and th e p o s s i b i l i t y t h a t th e mixed c o n d e n s a tio n p ro d u c t can i t s e l f condense f u r t h e r t o g iv e p o ly m e rs .

The l a t t e r i s e s p e c i a l l y t r u e

37

f o r th e p r e p a r a t i o n o f e t h y l d if lu o r o m a lo n a te , s in c e e t h y l d i f l u o r o — m alo n ate c o u ld c o n c e iv a b ly be more r e a c t i v e th a n th e o r i g i n a l c o n d en sin g e s te r.

To overcome th e s e f a c t o r s a new compound, p h en y l t r i f l u o r o a c e t a t e ,

was p r e p a re d , and t h e c o n d e n s a tio n w ith e th y l d i f l u o r o a c e t a t e was a tte m p te d . U n f o rtu n a te ly , t h i s compound i s i t s e l f u n s ta b l e to sodium h y d r id e , a p p a r­ e n t l y b e in g re d u ce d , a lth o u g h no a tte m p t was made t o i d e n t i f y th e re d u c ­ t i o n p r o d u c ts .

The fo llo w in g r e a c t i o n s may be c o n s id e re d a s t y p i c a l o f

th e a tte m p ts to p r e p a r e e th y l d iflu o ro m a lo n a te and o t h e r m ixed co n d en sa­ t i o n p r o d u c ts . E x p e rim e n ta l P r e p a r a tio n o f P henyl T r i f l u o r o a c e t a t e .

A 1- l i t e r , 3 -n eck ed

f l a s k was eq u ip p ed w ith a s e a le d s t i r r e r and two Dry I c e r e f l u x conden­ se rs.

I n th e f l a s k w ere p la c e d 100 m l. o f b e n zen e, 80 g . (1 m ole) o f

anhydrous p y r id in e , and 90 g. ( l m ole) o f p h e n o l.

One hundred tw e n ty -

e ig h t grams (0«95 m ole) o f t r i f l u o r o a c e t y l c h lo r id e ( p re p a re d i n 97.7% y i e l d from th e sodium s a l t e f th e a c id (U8) and phosphorous p e n ta c h lo r id e ) was th e n d i s t i l l e d i n t o th e f l a s k th ro u g h one o f th e c o n d e n s e rs . A ll o f th e t r i f l u o r o a c e ty l c h lo r id e r e a c te d , w ith th e im m ediate form a­ t i o n o f a w h ite p r e c i p i t a t e .

The s o lu tio n was th e n r e f lu x e d f o r t h i r t y -

s i x h o u r s , c o o le d , f i l t e r e d , and r e c t i f i e d on a c o n tin u o u s g la s s s p i r a l p ack ed column r a t e d a t 5 t h e o r e t i c a l p l a t e s t o g iv e lUO g . (77.5% ) o f th e cru d e e s t e r , b .p . 1U5**6°* c o n ta in in g some su b lim ed p y r id in e h y d ro o c h l o r i d e . The sam ple was r e c t i f i e d u n d e r vacuum, b .p . 5U-6 /2 5 mm., and a sm a ll p o r t i o n c a r e f u l l y p u r i f i e d on a 9 - p l a t e , c o n c e n tr ic - tu b e colum n, b .p . 1U 6 .1 °, nj?° 1.1*228.

38

XnaûL• C a lc d . f o r CgH^F^Og: C9 50• 55$ H, 2*63.

Found. Ct 50*50,

H, 2 .5 5 . M-ivad C o n d e n sa tio n w ith E th y l C a rb o n a te *

A 500-ml *, 3 -n eck ed

f l a s k was e q u ip p ed w ith a s e a le d s t i r r e r , d ro p p in g f u n n e l, and r e f l u x c o n d e n s e r.

P r o v is io n s w ere made t o m easure th e e v o lv e d g a se s by d i s ­

p la c e m e n t o f w a te r .

The sy stem was f lu s h e d w ith n itr o g e n and m a in ta in e d

u n d e r anhydrous c o n d itio n s d u rin g th e r e a c t i o n .

I n th e f l a s k were p la c e d

38 g . (0*322 m ole) o f e th y l c a r b o n a te , 125 m l. o f anhydrous d io x a n e , and 7 «72 g . (0*322 m ole) o f sodium h y d rid e *

Twenty grams o f e th y l d i f l u o r o ­

a c e t a t e ( 0 * l6 l m ole) was added d ro p w ise to th e r e f lu x in g s o lu t i o n o v er a p e r io d o f f o u r h o u rs w ith g ra d u a l d a rk e n in g o f s o lu t i o n ta k in g p l a c e . The s o l u t i o n was th e n s t i r r e d f o r an a d d i t i o n a l f iv e h o u rs , c o o le d , and filte re d .

Vacuum r e c t i f i c a t i o n o f t h e f i l t r a t e gave o n ly U m l. o f

l i q u i d b o i l i n g above th e b o i l i n g p o in t o f e th y l c a r b o n a te .

E th y l c a r ­

b o n a te (100 g .) was added t o th e s o l i d s e p a r a te d by th e f i l t r a t i o n , and th e m ix tu re a llo w e d to s ta n d f o r one week, a f t e r w hich i t was p o u red on to c ru s h e d i c e and a c i d i f i e d w ith a c e t i c a c i d .

The m ix tu re was e x tr a c te d

c o n tin u o u s ly w ith e t h e r , and th e e t h e r e x t r a c t was d r ie d and vacuum d i s ­ tille d .

No compound was fo u n d to be p r e s e n t i n th e d i s t i l l a t e e x cep t

e th y l c a r b o n a te .

A p o t r e s i d u e rem ained w hich was s o lu b le i n d i l u t e

b a s e , w a te r , o r e th a n o l, b u t upon a c i d i f i c a t i o n form ed an in s o l u b le t a r . Mixed C o n d en sa tio n w ith E th y l T r i f l u o r o a c e t a t e .

U sing th e

same a p p a r a tu s a s i n th e p re c e d in g e x p e rim e n t, a s o lu t i o n o f 37*2 g . (0*3 m ole) o f e th y l d i f l u o r o a c e t a t e and 7U g* (0*52 m ole) o f e t h y l t r i ­ f l u o r o a c e t a t e ( p re p a r e d i n 80% y i e l d by G ilm a n 's (15) method) was added d ro p w ise o v e r a p e r io d o f one h o u r to a r e f l u x i n g m ix tu re o f 7*2 g .

39

( 0 .3 m ole) o f sodium h y d rid e and 200 g . o f anhydrous d io x a n e .

A f te r

f o u r h o u rs , th e e v o lu tio n o f h ydrogen c e a s e d (U .5 l i t e r s ; 5$% o f th e o ry ) and th e m ix tu re was a llo w e d to s i t o v e r n ig h t a t room te m p e r a tu re .

Vacuum

d i s t i l l a t i o n fo llo w e d by r e c t i f i c a t i o n gave ^ m l. o f e th y l c a rb o n a te , b . p . 1 2 2 -5 ° , n ^ l . 3 8 5 0 . p o in t.

No o t h e r compound was found above t h i s b o i l i n g

The p o t r e s i d u e from th e o r i g i n a l d i s t i l l a t i o n was n e u t r a l iz e d

w ith a c e t i c a c id and i c e , and th e o rg a n ic m a te r ia l was e x t r a c te d w ith e th e r.

The e t h e r e x t r a c t s w ere d r ie d and r e c t i f i e d to g iv e 5 m l. o f

im pure e t h y l 20 ^ 1 .3 7 1 8 .

e t ,e f ,> ,> - t e t r a f l u o r o a c e to a c e ta te , b . p . U2.5-li5»5>°/6 mm.,

Summary A ttem p ts t o condense e t h y l d i f l u o r o a c e t a t e w ith o th e r e s t e r s o r a c i d c h l o r id e s i n a mixed a c e t o a c e t i c e s t e r c o n d e n s a tio n w ith sodium h y d rid e h av e b een u n s u c c e s s f u l.

However, i n th e i n v e s t i g a t i o n w ith a c id

c h l o r id e s two new compounds w ere p r e p a r e d .

The p ro b a b le s t r u c t u r e s o f

th e s e two compounds a r e g iv e n , t o g e t h e r w ith a re a s o n a b le mechanism and c o r r o b o r a tin g e v id e n c e f o r t h e i r f o rm a tio n .

These compounds r e p r e s e n t

an u n u s u a l exam ple o f a c y l a t i o n o f a h e m ik e ta l w ith o r d in a r y r e a g e n ts , t h e i r e x is te n c e i n d i c a t i n g t h e u n u s u a l b e h a v io r o f th e k e to group p r e ­ s e n t i n e th y l

O d ,e t,> ,V - te tr a f lu o r o a c e to a c e ta te .

P a rt I I I ATTEMPTED PREPARATION OF DIFLUOROKETENE

Ill

I n tr o d u c tio n The p u rp o se o f t h i s r e s e a r c h was t o p r e p a r e d i f l u o r o k eten e and to s tu d y i t s p r o p e r t i e s .

I t was a n t i c i p a t e d t h a t such a p r e p a r a ti o n

c o u ld c o n c e iv a b ly be q u i t e d i f f i c u l t s in c e th e r e i s no r e c o rd o f any d i h a lo g e n a te d k e te n e h a v in g been p r e p a re d , w h ile s e v e r a l a tte m p ts to p r e ­ p a r e th e s e compounds have been u n s u c c e s s fu l (ItU) •

I t was b e lie v e d t h a t

any d i f f i c u l t y e x p e rie n c e d i n th e p r e p a r a tio n would b e due to th e p o s tu ­ l a t e d h ig h r e a c t i v i t y o f th e compound.

Many r e a c t i v e k e te n e s have n e v e r

b een i s o l a t e d a s th e monomer, s in c e upon b e in g form ed th e y d im e riz e s p o n ta n e o u s ly (3 1 )•

However, t h i s k e te n e s h o u ld be a lo w - b o ilin g gas

s in c e k e te n e i t s e l f b o i l s a t - 56° , and d if lu o r o k e te n e would l o g i c a l l y be e x p e c te d t o b o i l even lo w e r, h av in g no hydrogen f o r hydrogen b o n d in g . As su c h , i t seemed p o s s ib le t h a t th e monomer c o u ld be d i s t i l l e d from r e a c t i o n m ix tu re s and r e a c te d im m e d ia te ly . The p u rp o se o f p r e p a r in g such a compound was tw o - f o ld .

In

a d d i t i o n t o g iv in g s y n th e t i c c h e m is try an e x c e lle n t r e a g e n t f o r th e a d d i t i o n o f th e d i f l u o r o a c e ty l g roup, i t was b e lie v e d t h a t th e dim er i t ­ s e l f s h o u ld g iv e q u ite i n t e r e s t i n g r e a c t i o n s .

However, i n a d d iti o n t o

a l l th e r e a c t i o n s n o rm a lly e x p e c te d o f k e te n e s , th e r e e x i s t e d th e p o s s i ­ b i l i t y t h a t th e e le c tr o n e g a tiv e f lu o r i n e atoms w ould ca u se r e v e r s e a d d i­ t i o n w ith r e a c t a n t s .

Thus hydrogen f l u o r i d e m ight r e a c t w ith d i f l u o r e -

k e te n e t o y i e l d f l u o r a l i n s t e a d o f th e e x p e c te d a d d itio n p r o d u c t, d i ­ f lu o r o a c e t y l f l u o r i d e .

W hile th e p ro p o sed mechanisms f o r th e r e a c t i o n s

o f k e te n e s do n o t p r e d i c t such r e v e r s e a d d iti o n s , th e p o s s i b i l i t y was to o im p o rta n t to be o v e rlo o k e d . I t i s now b e lie v e d t h a t e v e ry known g e n e r a l m ethod f o r th e

U2

p r e p a r a t i o n o f k e te n e s w hich was b e lie v e d t o be a p p lic a b le f o r th e p r e ­ p a r a t i o n o f d if lu o r o k e te n e h as been a tte m p te d .

I n a d d itio n , s e v e r a l

m ethods w h ich , th o u g h a p p lic a b le o n ly i n p r e p a r in g s p e c i f i c k e te n e s , seemed a p p lic a b le f o r t h e p r e p a r a ti o n o f d if lu o r o k e te n e w ere a tte m p te d . T hese m ethods may be d iv id e d i n t o two g ro u p s:

th o s e i n w hich an i n t e r ­

m e d ia te i s r e a c t e d w ith o th e r ch e m ic a ls t o p roduce th e d e s ir e d p ro d u c t; and p y r o l y s i s r e a c t i o n s w h ere in an in te r m e d ia te i s crack ed by h e a t i n t o two o r more fra g m e n ts , one o f w hich w ould be d if lu o r o k e te n e .

No t r a c e

o f d if lu o r o k e te n e was found i n any o f th e s e r e a c t i o n s , a lth o u g h a com­ pound was p r e p a re d w hich i s th o u g h t to be a 1 o w -m o le cu lar-w eig h t polym er o f d if l u o r o k e t e n e . I n g e n e r a l, no a tte m p t was made t o i s o l a t e d if lu o r o k e te n e a s such.

I n s t e a d , th e r e a c t i o n g a s e s w ere p a s s e d i n t o s o lu tio n s c o n ta in ­

in g a n i l i n e , and th e n th e s o lu t i o n s were a n a ly z e d c a r e f u l l y f o r th e p r e ­ sen ce o f d i f l u o r o a c e t a n i l i d e .

T h is method was t e s t e d and found c a p a b le

o f d e t e c t i n g th e e q u iv a le n t o f l e s s th a n 0 .6 g . o f d if lu o r o k e te n e .

In

a l l e x p e rim e n ts t h i s s m a ll amount o f d if lu o r o k e te n e w ould r e p r e s e n t a n e g l i g i b l e y i e l d , and th u s th e ab sen ce o f d i f l u o r o a c e t a n i l i d e i n th e a n i l i n e s o l u t i o n s was ta k e n t o mean t h a t th e r e a c ti o n was u n s u c c e s s fu l i n p ro d u c in g d i f l u o r o k e t e n e . As a r u l e , no a tte m p t was made t o i s o l a t e o r i d e n t i f y o th e r r e a c t i o n p r o d u c ts , s in c e th e s o le p u rp o se o f t h i s re s e a r c h was th e p r e ­ p a ra tio n o f d iflu o ro k e te n e .

I n a few c a s e s , new compounds have been

made i n th e p ro c e s s o f p r e p a r in g n e c e s s a r y in te r m e d ia te s and as by­ p r o d u c ts o f th e r e a c t i o n s .

These compounds have b een p u r i f i e d and th e

p h y s ic a l c o n s ta n ts g iv e n , b u t no a n a ly s e s w ere made, s in c e i n m ost c a s e s th e i d e n t i t y o f t h e compound i s r a t h e r o b v io u s.

k3

R e a c tio n o f C h lo r o d if lu o r o a c e ty l C h lo rid e w ith Zinc D is c u s s io n P o s s ib ly th e o l d e s t g e n e r a l method f o r th e p r e p a r a ti o n o f k e te n e s i s th e d e h a lo g e n a tio n o f e C -h a lo a c y l h a l id e s by z in c i n e t h e r o r e t h y l a c e t a t e (I4I ) .

By t h i s m ethod, k e to - k e te n e s a r e p re p a re d i n good

y i e l d s , b u t a ld o - k e te n e s i n o n ly 5-10/6.

The y i e l d s d e c re a s e s h a r p ly

from ot-brom oacyl brom ides t o o