A study of the oxidation of pyrethrosin

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4 s w m or t m o x m x n o * or f t m r m o n *


Phillip J. Ii*s**»

?&t*i* *ufc»itted fce tht F*e«it|r of t&i i.iaftiteta Sttoel tf tilt Ual*tr»ity tf v*ryl»Ad it ftrllAl fulfill— at tf tt» afiiaMfiti for tat 4tgrtt tf Setter tf Ft! loeophy 194a

UMI Number: DP71178

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The author wiehee to express appreolation for the help end encouragement given hi* by Dr* Hathaua L. Drake during the course of this research.

table m

cgwtents Page

I. XI.






Discussion of the Csonlzatton of Pyrethrosln Pyrethrosln, A Secondary Alcohol




3 d

Discussion of the Determination of Methyl on Carbon *•••*


Discussion of Other Oxidations of Pyrethrosln ..........


Discussion of Absorption Spoolrum of Pyrethrosln •••....•


Pyrethrosln, A Mixture of Isomera



EXPER1MEWT.*L P A R T .................


Purification of Pyrethrosln .............. Oxidation of Pyrethrosln by Selenium Dioxide

It .....

Ozonization of Pyrethrosln Compounds......... Description of the Czoniser Experiment I Experiment II


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

It 15 15 15 17

Experiment I I I ......


Ozonlzation of Pyrethrosln in Ethyl Acetate


Ozonlzation of the Syrup Obtained by Alkaline Hydrolysis of Pyrethrosln ........


Oaonlsation of Clhydropyrethrosln........


Sold from Cs on last ion of Pyrethrosln.........


Investigation of the Chloroform and Ethyl Acetate Soluble Matter from Csomizatlon ......... .


Attempts to Decompose the Osonldee of Pyrethrosln Catalytleally ...........


Ozonlzation ©f the Product Obtained by Pyrolysis of the Dlasomethane Adduot of Pyrethrosln......... . Preparation of Dehydropyrethrosln......


Page Preparation of the ?94~Dlnltr© pheny Ihyd raiton© of * Dehyd ropyreth ro sl a ............... Preparation of Dehydrodihydropyrethrosin

•• .....

?6 P7

Preparation of the 9#4-Di»it rophenylhydrasone of Dehyd.rodi hydro pyrethrosln ....... ........... .


Preparation of the Oxime of DehydrodihydropyretbroslA .••


Attempts to Inorease the Yield of Ketones from Pyrethrosln end Dihydrepyrethrosia

...... .


Datemination of Methyl on C a r t o n ....... ...............




Active Hydrogen Determinations of Dihydropyrethrosln and Dehydropyre thro sin ..... .............. .............


Investigation of Iroduots Obtained by Drastic Hydrogena­ tion of Pyrethroein .... ..................


pQtassiim Permanganate Oxidation of Pyrethrosln ••••..«••


Oxidation of fyrethrosin with Hydrogen Peroxide • ..... .


Other Unsuccessful Experiments with lyre thro sin


Oxidation of Pyrethrosln Aeoording to Oppenauer

Absorption Spoett u b of Pyrethrosln





SUMMAPY AMD CONCLUSIONS ................................



BIBLIOOPAHIY.......................... ...................



The hiatoiy and characterisation of pyrethrosin as a chemical Individual hat been thoroughly discussed by Stanton (29)« The research conducted by the author was directed toward the same goal as that of Stanton in that it sought to discorer the structure of pyrethrosim*

dhen the author began work on pyrethrosln the molecular

formula was known to he Sj/yHfrg P y

Also known were the general physical

properties and the existence of an acetate group* a double bond* an act!re hydrogen* and a probable lactone structure* Neither the nature of the fifth oxygen atom nor the basic carbon skeleton were known*

Likewise* the relationship which the various

groups bore to each other was unknown* the condition of the problem suggested two broad avenues of attacks

First* an attempt could be made to determine the central carbon

system* the most likely means of attack being d©hydrogenation of pyretls* rosin or some of its derivatives and identification of the resulting hydrocarbons*

Second* attempts could be made to establish the nature

of the fifth oxygen atom* th® nature of the known doable bond* the possible existence of other double bonds* and th® relation which the known groups bore to each other*

Her® the most llxely aethod of attack

seemed to be degradation of the molecule into more simple structures by oxidation or other means*

Mr* H* P* Ar&spom (1) of this laboratory

had already started work on the dehydretaliation of pyrethrosln, so the author attempted a series of oxidative studies of the compound* The unstable nature of pyrethrosln and the peculiar mixture of substances which results whenever the acetate grouping is destroyed *

suggested that rather mild ©mi dative methods would probably be most proda©tiro#

The knowlsdge that pyrethrosln possessed at least one doubl

boatl ©eased osealsation to appear to be a good method of degrading the mol©©ale*

3m session

Discussion of the Qgonl cation of ryretfarosla. the ozonlzation reaction (14) he* been of snemout value in the solution of structural problems ty cleavage of unsaturated compounds* However, the complex mixture of aldehydes • ketones, acids, and peroxides which results fro® the various elavages of the oxonide, followed by secondary reactions, causes interpretation of the results to be none too simple*

This is particularly true when the molecule contains other

groups than double bonds which may be attacked by the ozone or during the decomposition of the oxonide*

The formation of polymeric csoaides

which cannot be broken up into desired fragments is also a great handicap to the value of the reaction*

There is also some evidence $ndloa-tlng

that not all osonldes have the generally accepted structure proposed by Stausdingor (2d) and consequently cleavage of the double bond should not always be expected*

The gentler methods of decomposition of ozonldes

developed by Whitmore (3 ,31) and ftsober ($) reduce the number of pro­ ducts, but these methods are not always applicable. The ozonlzation of pyrethrosln, unfortunately, is subject to many of the difficulties mentioned above.

Its oxonide could not be

decomposed by catalytic methods and apparently other centers than the double bond are attacked by the ozone or during the decomposition of the oxonide. Pyrethrosln is known to possess at least one double bond, yet it does not absorb ozone mole for mole in either chloroform or acetic acid.

It may be significant that pyrethrosln reacts with only about

seven tnenths of a mole of ozone per mole of pyrethrosln.

This recalls

4 Stanton1* (2$) observation that only about eight tenths of a mole of permonophthalic sold is consumed* in chloroform# per mole of pyrethrosln* Slaydropyrethros1a absorb# less than a quarter of a mole of osone before osone is detected in the exit gases• yet osone apparently attacks it because only a syrup could be obtained from ozonlzation of this compound* Probably the most sign!ficant product obtained from the ©soni~ satlon of pyrethrosln mas formaldehyde*

It was obtained in yield# as

high as forty five percent of theory for one mole of formaldehyde per sole of pyrethrosln*

It was identified a# the dimedone (30) derivative*

The formation of formaldehyde in minute amounts is common la osoaalysis reactions even when the compound being osonized ha* no structure which could logically produce it*

However* the isolation of formaldehyde in

such large quantities seems to indicate that pyrethrosln possesses a methyl!dene group*

The yield of formaldehyde was better than that

reported for many terpenoids known to have this structure (2 *26)* Blhydropyrethroein yields no formaldehyde on osoni ration so it would Appear that In this molecule the double bond adjacent to the methylene group has been hydrogenated* The presence of a ©ethylideas group Is very common in the sesquiterpenes (26 *22 *23*24) and their derivatives to which family pyrethrosln most probably belongs*

The methyl!dene group in the terpen©#

is often part of an isopropenyl structure which is almost invariably associated with an Isomeric form containing the 1sopropylid©a© group* This is true even with crystalline compounds in the terpsne series according to 3 rlguard (3 *26) and others.

Consequently a careful search

for acetone* as an ©son!zation product• was made*

ho acetone was found

nor could any methyl ketone or additional aldehyde be detected in the

prod Hats*

This seems to indicate that the methyl! dene group is probably

attached to a ring*

If the methylideas group is attached to a chain*

then it must be breached off at & point further than one carbon from the sod* The failure to secure a higher yield of formaldehyde than was obtained may be due to several causes*

Fy reth rosin apparently forms a

polymeric osonide which will be discussed later*

The formation of this

product would lower the yield of formaldehyde since oecleavage of the double bond occurs*

Also there is evidence that osone does not always

cleave the carbonic a rbon linkage in pyrethrosln but may make an epoxide such as that encountered by Jhtsleka and Haagon~Smit (21) in the osoaisaiion of the sesquitexpeaol* gaaiol*

The fact that pyrethrosln does

not appear to absorb as much as a mole equivalent of osone may also be significant*

The detection of small amounts of formic acid may also help

account for the failure to get nearly quantitative yields of formaldehyde* Otherwise* the formic acid is not significant since It would be expected where formaldehyde Is known to exist* Acetic acid was obtained by e&onisatien in about a fifty per* cent yield of theory for one mole of acid per sole of pyrethrosln* However* no acetaldehyde could be detected and hence it must be assumed that the acetic acid was not formed by cleavage of a double bond but rather come from a disruption of the acetate group known to be present in the molecule*

The possibility that hydrolysis of the ostonide leads

exclusively to an acid splitting on one side seems a very unlikely one. Treatment of ttjscsoalxed pyrethrosln in a m a n o r identical with the csoaide decomposition process did not hydrolyre the acetate structure so it must be assumed that oaoniaation causes the acetate group to hydrolyse more

easily* The syrup obtained by the alkaline hydrolysis of pyrethrosln gave a yield ©f formaldehyde about the sea# as that from pyrethrosln itself*

This would indicate that if pyrethrosln Is an enol acetate as

euggested by Stanton (29) « the eaoliration was not responsible for pro** duoiag. the double bond adjacent to the methylene group#

I.t does appear

to be true that osonlsatlon disrupts the acetate structure In some way, because osoniration In ethyl acetate and decomposition 'with boiling water yields a syrup which contains no acetate structure and appears generally similar t© the syrup obtained by alkaline hydrolysis of pyrethrosln* Two acids were obtained from the osonlz&tion ©f pyrethrosln in ethyl acetate*

The first was obtained from the water layer when the

osonide was decomposed by simply boiling it with water*

Analyses and

neutral equivalents Indicated that this acid had the formula Both the acetate and lactone structures in pyrethrosln were hydrolysed in the formation of this acid since the acid did not take up additional alxali after the first end point was reached*

The fact that no carbon

atoms were lost except those in the acetate structure shows that the ©son# did not cause a cleavage ©f the double bond*

This failure to

cleave the double bond is unusual, but cm# example of such an occurrence has already been mentioned in Rujtieka’a work on gualol*

Another example

is the work done by Korappa and ftoschlcr (12) on cL fenohene*

Any sup­

position that clerage did occur would indicate that the double bond was in a ring*

Other evidence does not bear this out* The above acid was obtained repeatedly but always in yields

of about tea percent*

Treatment of the decomposition mixture with hydrogen

peroxide did not increase the yield*

Attempts to prepare the acid by

7 hydrolysis of pyrethrosla* simply boiling with water and an organic solvent without previous ©son!ration> failed in all cases*


aoetat© and water and dioxane with water gar© book the pyrethrosln unchanged•

Acetic acid and water gar© only a syrup*

It is interesting to note that this asid differs from an acid prepared by Hose and Haller (19) from alkaline hydrolysis of pyrethrosln by only an additional ©sy^en ..atom*

This again suggests hydrolysis of

the aoetate structure and an epoxide oxygen across the double bond. The other acid obtained fro® ©thyl acetate osonlsation cam® from the ethyl aoetate layer of the decomposition mixture when this was allowed to ©raporate slowly*

It was obtained in very small amount and

could not be obtained again*

Analyses and neutral equivalent indicated

that it had the formula Op^%gG$*

This differs from the first acid by

an additional molecule of water* Gsoairation in both chloroform and as©tic acid gave a non0 crystal line product melting, with erolution of gas, at 360-370 • It was .

insoluble in ethyl acetate but dissolved in alcohol after first turning t© a gum*

It was precipitated by the addition of water and dried to giro

a solid which could be ground into a fine white powder*

Carbon and

hydrogen analyses indicated that It corresponded closely to the formula 3^yHbft0y»

It was not acid bat took up excess alkali ©a standing*


failed to react with any carbonyl reagents and gay© no free iodine with acidic potassium iodide*

Pyrolytic distillation gar© acetic acid*


substance is probably a polymeric osomide* The failure to obtain any crystalline aldehydes or ketones from the larger fragments of pyrethrosln or any pure carbonyl derivatives was a great handicap la the study of pyrethrosln by oxoaisatloa*


methods of decomposition calculated to give aldehydes and ketones in good yield wore tried (3*31} * bat all failed*

Th© thick syrups invari­

ably obtained* failed to gi v® tests for aid ©by dec and no par© ketone derivative was ever obtained*

it is probable that loss of the acetate

group with consequent formation of th© unworkable thick syrup which made progress difficult in other attacks on pyrethrosln ©as again responsible for failure to obtain pure compounds containing the greater part of the pyrethrosln molecule*

The formation of the polymeric otohides

and epoxide compounds also complicated th© invest!gatios* failure to obtain formaldehyde from the oxonlnation of the pyrolysis product from the d iesomethaite-py reth ros 1n add act indicates that dlasemethane adds across the double bond adjoining the methylene group* Fyrefchrosin* 4 Secondary Alcohol* four of the five oxygen atoms in pyrethrosln may be accounted for by th® acetate and lactone structures known to be present in the molecule (23)*

&o positive evidence as to the nature of th© fifth oxygen

atom existed when the author began work on th© problem*

Since all of the

many attempts to prepare carbonyl and hydroxyl derivatives had failed* it was assumed that these groups were absent or in some way powerfully hindered*

Mli©*yl determinations (4) shoe the absence of an ©thoxyl or

methoxyl group (23).

Th® possibility of an ether linkage between larger

fragments of the molecule existed* The possibility of the existence of a powerfully hindered hydroxyl group was suggested by Stanton9s (23) dissoveiy that pyrethrosln possessed nearly one equivalent of active hydrogen*


also possesses a little less than one equivalent of active hydrogen*

9* Th# preseoee of a 'tertiary alcohol would be la accordance urith most of this evidence* However,

Mol. wt* » 316.34 This acid would not take up any excess alkali ’ which was run in after the first end point was reached. A d d from the Ethyl Acetate Payer on Recomposition of Py rethrow In-Osonlde. The ethyl acetate layer from the eaont sation and decomposition of 4 grams of py rethrosl a was put in an open flask In the desk.

£hen the

ethyl acetate had evaporated to naif its volume some triangular ciystals were observed on the bottom of the flask* dried*

Tnese were filtered off and

The substance melted at 190° with docomposItion*

It was very

alightly soluble in ethyl aaet&te and chloroform but soluble la water

and alcohol.

Five resrystalllsatloas from hot acetone gave about 70 sag*

of small, hard or/s tala whieh melted at 219



with decomposition*

alight yellow tinge could not be removed by charcoal nor could the molting

point be raised*

The substance was acid.

4o It was dried in vacuo at 73

for 2 hours and analysed* H&« of Sample

itg. of

Mg* ef TOg