The photochemistry of the formation of sulfuryl chloride

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♦WSS S M f W Sflt W W



m Martin Christopher Londergan


Tbesi* Submitted to the Graduate Faculty for the Degree of DOCTOR

m $ m Mkjttst*


PHILOSOPHY theisiatrf




% © w & .

State College 1942

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UMI N um ber: D P 12102


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US45p table of contents

wm® BITBQDUCTIQlf*. ..s.**......**...******.*..******.* ******




.*.**. *.♦.*#

•HFlRIMEiTAL IMlfls^IQ&TIGli** **«****»«***.*.*•**«*.•****. . A.

Apparatus**......*.**....*.******.*.******..** 1. 2* 3.




Light souree*******.*..****.*..**•******** Reaction chamber and method of stirring**. Manometer and measurements*......

f f! S' 11

Bi*©parati C 135C1S7» and C 137C137 is the ratio 11*3 to 8*7 to 1.

being one tube of chlorine gas mm

a filter to remove all the light which could be absorbed by the Cl3gCl3& molecule* there should lie a larger freel ten of the light passing through the filter which could be absorbed by the C137C1 S7 molecule.

This light, which had already


th© first tube of chlorine, would then enter a second tub© .-that also contains chlorine gas*

This second tube would contain

another substance -b®ai#oa't..te§ oblorSafr; which would.- react with, the activated chlorine molecules*

The light entering the second

tub# could activate only the C 137C 137 molecule as all had been absorbed which would activate the C1 35C135.

The resulting

product after activation should contain a much larger percentage of Cl37 than one formed using the usual chlorine gas*

If art far

dioxide were the second molecule present, the sulfuryl chloride which was formed should be enriched in Clgy * *

These values are given by Elliot; Pros* Hoy. See. (London)» A123, 629-44. 3.989* *

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5In th®- choic® of a resetion of this type several factors had to b® considered,

There must of a©Oi»sity be isotopes

present' in the absorbing molecule in ®neb a ratio that th® light would b© selectively absorbed by one type of.the isotopic ssapOBent*

Tear© .should b® no chain reactions and y#ry.f#w.*.

if any, sido reactleas*

[email protected] tma t u m efficiency,,, which 1© the'

ratio of the mmhse. of molecules of the product f®r»«d to the number of quants of light.absorbed,.should be- ene« The reaction of .sulfur dioxide and chlorine upon, th® activation by aoMOChresatic light seemed to folfill thee# con*


it.«&#. assess*??.though that a thorough staty of

this reaction 'be mad® wader various experimental conditions before' a&sttsGipt could he nsde.ta aoparai®. the Isotopes of chlorine by-this method*

It is sa this phase of th® problem

that this .investIgatloa has been performed.

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Regnault (4) in 18X1 has given tie first recorded observa­

tion that sulfur dioxide and chlorine combine under the influence #f light.

W» #i#®rv#d that if the two gas®#


stiihsA maA «-*

posed to th® strong rays of the summer sun, a liquid condensed #s the walls of th® vessel*

lifeawia** he [email protected]#ft ttm* very

little or none of the liquid formed when the mixture was exposed t# the rays of the winter sua, indicating that the

reme^Xm wtm

probably due to the shorter radiations which would be much « * & * * during the winter months*

■tramt*. -ff! la- IW I smmmsvwX the vmpor ien«tei 'of iwlfnrfi chloride aad determined the decomposition of the gas in the region of 100° to 200° C.

From these data K® calculated th®

constants in the Bernsi specific heat equation, mast fro® ttufet* calculations be has given m curve to show th® deeompoa it ion of

the $»*pemat tmm ■-80® to 3©0* &« catalyst for if®

1% -mm- ■wmmmmy t® sat a

at ii® beaj^rftburit which h# vorfetd*

Activated «.tor®oal gave the best results in this dec capos it ion♦ in « t0bm paper Trauts

stowed that th® photochemical

formation of sulfuryl chloride gave a stationary concentration

which-was higher tfeats th# tfesmfttel #q«|Mbri»v «t ito wmm' temperature* L® llanc, Andrich and Eangro (?) uiMt# a study of th© .ptotochiffiical #yst«Bi of » mixture of sulfur dioxide, chlorine *a$

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auifuryi etslerM#. la order to establish the effect of light- of different wave lengths upon the reaction mixture*

fhe absorption

spectra of chlorine, sulfur dioxide ant neitvryl chloride -atsw. strong maxima in different regions of the spectrum,

That of

chlorine is about 3400 A, sulfur dioxide is about 3000


m ifuryl chloride shows a m a x i m of absorption below Hit# A* Ttstr afforded a method of studying the effect of light ap§» ttet atxtiir© which would activate only one of m b of molecules in the mixture*

of the three types

They found that light below 2300 A*

which ws#.absorbed by the suLftaryl chloride, caused decomposition Sato sulfur -digaids mmft chlorine as well £* possibly aon* other products is mm%& amounts*

When tie mixture was illuminated

with light t» th# m g £ m of lf©0 %

which was absorbed by the

sulfur dioxide, they found a slight decomposition of the sulfur dioxide but no other reaction,

if a mixture of sulfur dioxide

and ehloriise was illuminated with light above 3000 A, this lightbeing absorbed by the chlorine, the reaction proceeded toward the m m r n M r n #f iJfftfuryX chloride.

Air was present as &

to keep the chlorine and sulfur dioxide from coming in contact with the mercury in tb© manometerf water vapor and more air were aided in sea#, reactions-, but these t*w4 w m w little effect m formation #f aid furyl chloride*


Thus, they established the feet

that It is. tb© light which is absorbed by the chlorine in a mixture of sulfur dioxide and chlorine which causes the photo** chemical formation of sulfuryl chloride to take place* T r a m fsl indicate# that p m ® m € thoroughly dried .chlorine

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«t§ sulfur d i o x M ® isai to

moisture is present*

«®@fe store slowly 'tfesa-lf

Later work fey Schultae (9) has thrown

deufefc agfla this -work of Train. feaeasi** it i m shown In an extensive set of experiments that water vapor bad no noticeable offset on th© photochemical formatim of phosgene from earfeon monoxide sad chlorine*

this r#*ett#n tauS- sis# feton cists®# fey .Twbwi t* fee

strongly retarded if the gases sere thoroughly dried* Sonhoeifer (ID) fea* given an mpproxSis^fc® tainlfia effteiettey for the reaction of sulfur dioxide and chlorine as abotit one thousandth of that of phosgene*


HI* value® for 0 m g m m m m

This would fee about one or two of. the order of. 1 xi®^*

A «aanorlfe«a review shows that the reaction of sulfur dioxide

sad cIxlori»e- preeavft* Sm th® formation of sulft*yl chloride: wi»® 4 t mixture is illuminated with light that is absorbed by the chlorine#

The w o t ion has very few or no aide reactions and

h®@ « qmntasi efficiency which i# of the order of unity# reaction m m fee carried out at ordanery


and pros**

sora*. and, a# tfee*» is a change is.the aietfeer #f solemales during the process, the extent of the reaction can fee followed by noting the change in pressure.

previous s(fl «

One of th® objections! features In Ifee

this reaction fen® been the methods #f s»sux*iiig

pressure ctenges.

Corrections had to be made for ttss gases which

m m m absorbed in th® sttattneter. liquid during the extent fef th® 'reaction#

1» Blanc, Andrich and Kangr® (?) tried to overcome

this by having a cushion of air between the gases and the manometer 11qnfeiw 'but this method allowed .sir i® diffuse slowly ibpcmgfc the gaseous mixture*

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k* 1*


Llfiht source

A Itaswl Electric capillary fmtrt# snmrjr art tiff# H6) which operates at 80 atmospheres internal pressure «## use# tfcreagbftit t is© iwtttlgaiiiia*

I M s arc gay© an intent# festal

la th# hlu© region of the spectrum.

The capillary was made of1

fmsrtg a&cut 2.0 iub* inside diameter and 2.5 era. in length*

with tungsten elsetrod#®' sealed in each tad#

the at#; operated

In a horizontal position, surrounded by a p f r « water jacket

through which water flowed at % m rat# of abtafc '#1* quarts m aiaute.

It operated on 1200 volts from a General Electric

transformer and the total power input of the arc was about 1000 watt** The beam way# rendered approximately parallel by a cylindrical,

flats less with * focal length tf $* ws,

it wm. tb#» passed'

through two iris diaphragms to remove most of tbs light which was not parallel, ■ la th# ®xp#ri«#nts la- which monochromatic light was used, a Corning filter (Ho. 7) was placed between the two iris diaphragras to isolate th# 4SS8 A line of mercury.,

This filter allowed very

little light other than that of th# SOgCXg

On© volume of sulfur dioxide reacted with one voXuir® of chlorine t© give one teltw of sidfuffl chloride*

Thus, the**# was .a

decrease in the volxxm of the system as the reaction proceeded* The total decrease was equml to the volume of sulfuryl chloride formed* m m m l m the »iat ionshljn. .

ft - t m would hold ove*" this email range of


fiat usual methods of pressure measurement could not be

applied satisfactorily because of the corrosive nature of the


It m t n m m m m f that the

from less than 1 bib* wp to atmospheric pressure*


A combination

tnsaesia&H* and click gage describe! by Smith and fsylor se> covered

'm e + a l wskgVrY.



To morometer



T’icg.S. 5+orage +rap and click gage.

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-18-* cubic ceutlfficters .of the .pure liquid' which, was seeled storage trap*,

i' ® +r




the ,

m s kept in a freezing -mixture until,

tlie chlorlae was used op as the pressure'of the liquid €hlari&9 at room temperature was ubomt eight atmospheres, and this



too high a pressure, to be safe in ordinary pyres glft-gfisare* The purity of the gas m s cheeked fey feufetatng mercury in tl ich it completely dissolved*




slowly through

This proved to fee

the ®osfe efficient way of preparing dry chlorine free from any trace of oxygen or nitrogen*

Thor# was no contact with the

air after the system was pumped clown, end the powde** m & heated long enough to drive out any small amount of residual moisture which






have been present*

In the first runs* which were im&o m tank chlorine was used*

trial rims, -ordinary

A long induction period

w a s .

-found at

the start of the reaction, sonot lines thirty or forty bourse .and this could probably be duo



some impurities which were

present in -the tank chlorine* ' Tie reaction in the above prepars* tion is given





^ 2 CuCl * Gig

at a temperature of about 450* C. to Insure a slow steady .stream. Of chlorine ..gas* 8*

Sulfur dioxide The sulfur dioxide -was prepared by the action -of sulfuric

soil on sodium sulfite* Sag.8% ♦ 8 % S 0 4

* M Q | + % ® * 0O2

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■flie gas was

tteeigfa water which was aatueated with tlx©

gas to vmmm any water~soltxbl© gases which might tea present* It was passed through m sulfuric acid solution to m m m ® .any sulfur trioxide, i w c t i o m t e d slowly through a tube of calcium chloride to dry the gas, and sealed into a system similar t# that used for'the' frsctionattoia ‘of the' efi&aH&a




This system was evacuated after the sulfur dioxide was tresen solid with liquid air*

It was fractionated six time#

after the vacuum apparatus was sealed off, frozen out Into the storage trap similar to the one used for chlorine, and sealed m

th# U n t at

& , Fig. 1.*' This llqtiM 'was also jtapte

%n # freezing mixture to prevent the possibility of the pres* sure feeing toe .great for the pyre* g l m m * S*

sulfur?rl chloride ■ There have lees many catalyst# q m 4 to tba^ ppapacwtlaa

of this liquid; their use is described by Schwarz and Kunzer f!5>*

Activated charcoal heated in an atmosphere of

chlorine was used In the preparation of the sulfuryl chloride for the experiments to check the decomposition of this liquid at

a temperature near !§§•' C*

It was found that a mixture of sulfur

dioxide and chlorine, cooled to about *40° C* te the presence af the activated charcoal, was converted to sulfuryl chloride nearly one tuinSrsa. per sent within a few seconds.

At room temperature

the conversion 1#: slower and not complete.

The liquid m m

separated fro*. th# catalyst by tlstiilatim, under reduced pres*

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-80* ©ur® mad th# volatile gases were- p m p e d oil*

It, \«*s stored la

pp?«x traps# sealed off with this glaa* tips, which e e u M be broken after mm&ling the trap to the reaction b 4b la which the deeoi^posltioa was to take place*



1 « The reaction flw total ©lapsed time of tb# reaction warn usually of the order of ninety t* on® hundred fifty hoars# depending upon

th* prossares of th® gases present and the amount of light abiorheft during th® process*

The water Jacket aroaaft the mercury

arc, iist'lens, the window into the constant temperature box and th© window of the reaction chamber were all pyrex glass and very little light of « war® length loss than 4800 A could enter th® reaction chamber*

Chlorine was the only gas of th® wtxtor# of

sulfur dioxide# chlorine and sulfuryl ohlorid® which absorbed■ ' radiation in this region of th® spectrum and, •# Chlorine was th® only absorber# bins amount of #n#rgy absorbed by th* M m tor® was dtrectiy proportional to th® p m m w m of th® ohlerte# prosest* The temperature of the reaction was 70° C.

The tot at pres­

sure of the reactants was never greater than at!»»pl»rfe pleasure# and under these conditions the sulfuryl chloride which wsm formed remained in the gaseous::state*

Sulfuryl chloride boll® at

70° C. at one atmospheric pressure.

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The uiial procedure which was followed la carrying out a ' reaction began with the ©vacation of the system after the storage traps of s«l.f«r dioxide and chlorine had been sealed t© the lias fS» mtA 1®* Fig.* 1J*

Stopcocks at | % and % |

ware closes Soring the process.

connected tbs apparatus

to the ataospher# and C3 was the stopcock between the click gage and the **xseM»t#r«

It was ssssssorp to have a by-pass

around the click {gage {12, Fig* 1) so that the evacuation woxild not take pi as# against the t him .glass diapMtga#


protected the gag« and by careful manipulation the one diaphragm was used throughout this set of experiments.

The evacuation always "took over tea hours, and sometimes two days, and was carried out with the -reaction clamber heated to I t # 8*

This heating was mamtwrnef to reasve the last

traces, of |ii«# adhering, to the walls of the reaction chamber. The progress ©f the evacuation was followed on. the Me&aod gage {18, Fig. 1),

This'gage was with three stages, and

pressures could be- read frost sue millimeter down to a flat

vacuum. The system was always evaemfei 1© a presswe of less than 10“5 mm. Bg* After the evacuation was eoapieted the by-pass around

the -click .gage- was sealed off-mt %

and % , Pig* 1*


S.S2) cm. S O a

T IM E . ( H o u r s )

fig* #*,

Experiment 12


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*# *-*© . in atmospheres* was calculated

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from the experimental values for tbs dissociation of -snlfuryi ehlorid* tjf ibs/«t®tsii.iaiit Xp ■



f ■ prsftiiur# in fttflMptuffftft

1 -oO2 f&» «xpiria«tal values.- for ila» dlssoelAtioik *ad the calcu­ lated values of' Ip ore given ta Table li * fable 11 Dissociation and Equilibrium Constant

Temperature* °e.

pressure* mm.*




Kp (Atmosphere}













. m§ m v ® r n m to

o° c. .

fbe «wa&l£ferta» ooaotsisit increases with [email protected]«rmfur# a s tbs a s Is positive saS heat Is absorbed in the process of dissosIati«* .An Increase In pressure decreases the degree of dissociation at may temperature altteugh' the equilibrium oonstant remains -tba fl«a»» This would be expected because there- i& as increase

la the number of welsculss as tbs reaction proeeede# t M an added pressure would turf to force "the reaction haeh towards

the lower pressure# The heat of the reaction 4 AS) m m b# dotoraiaed from the values of Kp at two temperatures from the Integrated equations

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f M s gives « 'tslis for A H of 12,910 calories with. the substlU&£«& #f the values of Kp; g l v « above at the tMpmnttur* ©f 85 and 100° C.

! ft» hypothetical heat of reaction at sbsolaie *«re (A H 0) is w m GdmmtkmBt*- aacwing. 'th» heat saptsiiy reieileija will hold down to absolute seroi


= AIS +/ A CpdT /o

The v a lu e o f

A S p ■ f p (p ro d u c ts )

- Cp ( r e a c t a n t s )

the valu# for A c p for the dissociation of ealfmryl chloride fees been give®.If Arii (S3) as* A f p =-1.1

+ .0G81

- 1*J36 X 10~6f 2

T&e e^asbiiwbioii. of this 'vmlae into the efuatloni A»

=A10 +


vw& 'lnteg»tlagf As

= A H c - 1.1T ♦ * * 10“3T 2 - .62 x

this gives a value of A %


A S # = 12,795 eal

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using the A B 'gfiren « t » w si. 1 © # S* i M sssuning A S ©onsifiiit over the 15® temperature range between $5 •and 100® C. fte© Integral ion ©oastamt HI' ««. now tee osloiasiea using [email protected] a E q of the rest'tlen sad. the free energy ©bang® (A F ) mm #a^O#ted. frost* Af

= -2,303 RT logKp

& « 1*98? Ep = 3,098 at 100° G, (experimental value)

A P * -2,303 X' l*fm X 373*1 -log.. 3,098 * -838 cal.

AW * Amq +1,1 x' 2*308 f log f - a*0 X I©~3#

+ ,21 X 1©"%^ + If

Substituting the walae# for A ? at 100® G. sad A V - 8®

=M , ? f & +

1*1 x 8*303

X 873*1 log 373*1 -* * I©**3

X 373.12 + *21 x 10“6 X

373.13 ♦ If

I = -42.18

fte© average mitt® #f I fo-tatd from lb© A f at the three experimental temperatures east

I = -4t*2§ fb© general equation for the calculation of the free energy at say temperature for the dissociation of sulfuryl chloride 1© givent A W * 12,798 + 2*53 T 'log T -* 2*© x I©*-3#2' + *21 X I©*3# — 42,267

this equation was mwtA to calculate the vslm© for A F at 40° C,» at which temperature Aril has given m

experimental value for' Kp,

this ealeulated value of A f was found to be:

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8 gives a calculated value of Kp «i this temperature: Kg* ©.10 atm. at 40° C. The m m m e*peri®entai value given fey Art! m e t Kp* 0.051 atm. .at 40° C.

Following the same procedure the value of Ip was obtained at 110.5° C.

frnmm'mrn given an ^ferftnsaisl valued

Ip * 3*7 at 110.5° ©* with a poeslhl# error of [email protected] value of Kp calculated from the- above



front this investigation -*&£* lp * 4.7 at 110.5° §*. these calculated constants show fair agreesieift with the «**■ periment&l 'wains# of the' otter investigators in the temperature ranges is which their data were determined*

the data given

fey Aril m m ® need to ©aleulats the value of Ip at 110*5


Ihis: data wore obtained between 30 and 50° C*}: Ip .m 1*03 at 110,5° C. the #tuatl« reported by Iraatm gave the following values Of Kp.


" Sp * 28.6 at 110.5° C. Ip = #*#4 at 11©*# C.

&* -©aicuiatiOB. of the- Free User Enough data have been. found available in the literature to calculate the .free energy of the molecule {SOgClg) ■statistical methods*

ftiea# data are- nsessseryi

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1.* iritamttonal frequencies of the molecule from lasaa spectra (34X35)*


Slestron diffraction mine#' which shew its® m % m n lar model* the positions of the *te«is> sal %bo interatomic distances (36)*

The steps in the calculation of the free energy are*. „ 1 * .Assignment of the vibrational frequencies to the

'various modes of vibration* S*

Bwsliaate the translational and rotational contributions of tli® 'molecule to the m % m m

%^r “ i

+ 1I2jlf ~ m m

bar the equation:

*' f S i s « + 863*869


M ■ molecular weight * = gfwetry anafee* ABB = product of ifa® principal Moments of inertia of the molecule* 5*

twaiuat# the contribution of th# sllxnttlsiis t# the entropy :#f the molecule.


the m i n e of the free energy is. obtained from the- sum Of the contribution of the translation, rotation and vibration to the free energy* .

! fbe:electron diffraction patterns.. ■Warn that the moleculels a distorted tetrahedron with the 'sulfur in the center*


£*Q distances m m 1*43 A and the S»tt dlsfsooos are 1*99 A* ft» © S O angle Is ll®0 48* and the ©1 I 01 angle is 111