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7? ?1rxa Ha/ 1974 BHS(Ol) Photochemical Reactivity of Vinyl Chloride R.A. Cox, A.E.J*. Eggleton and SandaXl* *3v "feivironmeatal: and Kedical Sciencea Division, AE2B,: Earvellj Oxfordshire, OXU ORA, AP00018357 The Photochemical Reactivity of Vinyl Chloride . Contents 1 Introduction 2* Pho'to-oxidation Experiments 3* Hydroxyl Radical Attach on Vinyl Chloride 4 Comparison of Reactivity Date with ether Investigators 5* Products of Vinyl Chloride Photo-oxidation 6* Eye Irritation 7. Conclusions , 8. References Pegs t 2 4 7 7 8 9 10 Table I Rats paranetere in photo-oxidation of vinyl chloride and sons hydrocarbons Table IX Relative photochemical reactivities lie* Ccnccr.trc.ticn tisc currcc fer the photc-cxidatioa of vicyl chloride in the presence of NO Pig, Z pig* 3 Plote shoving the romaval of olofin and NO during photooxidation .... Ozone formation during the photo-oxidation of hydrocarbons and vinyl chloride Pig. 4 The effect of added vinyl chloride on the photo-dissociation , of nitrous add .Pig* 5 Plot of the rate data from the photolysis of HN02-olefla Mixtures according toequation (i) 11 ^ 12 13 14 15 16 17 (i) APOOO18358 fiiS-74(0t; \ Introduction The formation of * photochemical smog* In polluted atmospheres results from . the oxidation of hydrocarbon substances in a photochomically initiated reaction involving oxides of nitrogen* The oxidation, products characteristic of photo* chemical smog inolude oxidants (mainly O2ono), aldehydes, C0r orgaaio nitrogen compounds and nitrio acid*. The relative importance of the various hydrocarbons which ore emitted into the atmosphere in producing photochemical smog in a given area depends on the rate at which they undergo photo-oxidation. Investigators have drawn up an empirical scale of reactivity which is' baaed on the measurement of certain rate paranotera for the oxidation of individual hydrocarbons in - laboratory experiments, carried out under simulated atmospheric conditions* The parameters most widely used for comparison are (a) the rate of conversion of KO to KOg ^ \w/ ihe rate o* uyurvearbun vunuumpuxoj), and (e) the rate of ozone formation The following general- order of reactivity has. been established^ * I Internal- > polyeubstituted y terminal y mono alicyl y paraffins olefins benzenes olefine benzenes % The reactivity of a given hydrocarbon may be ascertained by comparing measured values of the above parameters with those for other hydrocarbons which have known reactivity*^: ;f ' __ * Hecentitheories- concerning the mechanism of the hydrooarbon^C^ photo* vw* ^ oxidation havs suggested- that the major free radical apeoies involved in tho initial attack on the hydrocarbon is Hie hydroxyl radical, 03* There is accumulating experimental evidence which confirms this* In particular the rate of OH reaction with aliphatic hydrocarbons corresponds closely to the empirically determined photochemical reactivity for both .unsatur&ted and* saturated compounds* * Although a similar correspondence is found for atomic oxygen and ozone reaction with olefins, the reactivity of 0 and 0^ with saturated hydrocarbons is too slow ^ -1 - APOOO18359 to account far tho observed photochemical reactivities of this class of hydro** carbon*. Zzl order to determine the photochemical reactivity of vinyl chloride two series of experiments have been carried out. Firstly, tho rates of photo** oxidation of ppm concentrations of vinyl chloride, ethylene, propylene and trans-2-buten in tho presence of't ppm NO in air were measured and the rates compered* Secondly, the reactivity of these four olefins with hydroxyl radicals was measured by a technique recently developed in these laboratories^ which uaeo the photolysis of caseous nitrous acid as a source of hydroxyl radicals* 2* Photo-oxidation Experiments (a) Procedure Mixtures containing part-per-aillion concentrations of olefine and nitric oxide in synthetic air were mads up in a 200 1 flexible bag constructed of Tedlar film. There was no detectable adsorption of olefins, NO or N02 on this material {loss rate < hr"1). Ozone loss rates vbfe measurable (**105* hr"1} but not serious* The bag was irradiated by two banks of fluorescent lamps which had a broad spectral intensity in the blue-UV region (300 - 430 nm) with maximum intensity at 365 nm. Tho Tedlar film is transparent throughout this region* The light intensity was approximately 75^ of that of natural sunlight (zenith L 40) in this spectral range, as measured from the rate of photolysis of N02 in pure nitrogen. (k^CNO^ed 0.27 min'1). Synthetic^ air was made up by introducing 50 1 breathing grade oxygen to the bag and. filling tet 240 1 with nitrogen (oxygen free grade)* The trace gasea, olefins and NO were added to the N2 stream during filling* After allowing' ten minutes for thorough mixing, the mixtures were irradiated and the ooncentra-- tions of the olefin, the oxides of nitrogen NO and N02 and the ozone was determined as a function of time* The relative humidity of the air in the bag was approximately 20 + 3& and the temperature 22 2C* Analysis of NO and N02 was carried out using a chemiluminescence NO^ analyser -2- AP00018360 (TECO Modal. 12a). Ozonv va* measured os a Nedorbragt type ethylene* ehemf-- luminescence ozone detector, end the olefine vers measured by gas chromatographic analysis uaingjt flame ionisation detector. The minimum detectable concentration* t using each of these techniques vas of the order of 1 ppb and the precision at the 1 ppm level vas better than e Materials* hitrlo oxide vas taken from a standard mixture containing US ppa HQ lii H2* Ethylene (99.6$), propylene (99$). trano-2-butene (9956) and Vinyl chloride (99*95$) vere taken from 'lecture bottle1 cylinders (BDJJ Ltd). No impurity vac detected either by gas chromatographic or infra-red spectroscopic analysis of the vinyl chloride. (b) Results A. Photo-oxidation of vinyl chloride in the presence of NO Fig* 1 shows tho concentration, time curves for the reaction of' 2.21 ppm CgB^Cl rttb 0.97Q ppm NO under continuous irradiation. A typical, thoui rather slow, 'photochemical smog1 type reaction ie observed} after a short induotioa period, oxidation of NO to N02 commences with accompanying `consumption of the vinyl chloride and aa the NO la depleted, the concentra tion of osone rises. Even after six hours irradiation, oxidation of NO vas incomplete end only 26^ of the vinyl chloride had been consumed* After prolonged irradiation (22 hours), 79/6 of the vinyl chloride had been * consumed and tide osone concentration had increased to 0.60 ppm. Thus, significant osone concentrations result from the photo-oxidation of vinyl chlorider iik air but only after a long period of irradiation. B. Comparison of the rates of photo-oxidation of vinyl chloride with hydrocarbons Similar experiments to those described above vere carried out for ethylene, propylene and trans-2-butene with initial concentrations of .'2.36, 1.67, 2.10 ppm respectively. Initial NO concentrations wore 1.02, . -3- AP00018561  0$19 0*97 pfo respectively* Fig, 2 shows the concentration time curves for removal of NO and the olefine# Clearly the reactivities of trans-2-tniten* * and propylene are much higher than that of vinyl chloride which Is similar to ethylene. The absence of a noticeable induction period for NO oxidation with propylene arises from the presenee of * higher initial concentration of NOg in this experiment {(NOg)Q 0,10 ppm for compared with < 0*05 for the other hydrocarbons). The ease order of reactivity is alee evident from the plots for osono formation shorn in Pig. ? A quantitative comparison of the photochemical reactivity can be made on the basis of a number of parameters* For the present discussion v* will consider the following:- (l) Tho average rats of NO oxidation to 50it NO consumption (b) She amount of roaotant consumed after a gives time (4 hours) 4 (c) The maximum, rate of ozone formation; (p) The final osono concentration after essentially complete oxidation of NO. The numerical values for these parameters, estimated from the concentration time curves ere given In Table X* * On the basis of parameter Af the reactivity of vinyl chloride is rather close to that of ethylene but in terms of hydrocarbon reaction rate (b) vinyl, chloride oxidation is significantly slower. Both compounds are considerably leas reactive than propylene end trans-2-butene* For all four substances* the final ozone concentration vaa approximately the same, shoving that the chlorinated, hyddocarbon* vinyl chloride? can potentially produce oa much ozone as the *reactive( olefina but only after a much longer reaction, tine* 5, Hydroxyl Radical Attack on Vinyl Chloride (a) Procedure ' Mixtures containing e ppm gaseous nitrous add together with approximately -4- ' ' AP00018362 0*7 PPM each of KO and liO^ diluted la a N2-02 mixture (2tf) were made up la. the Teller bag- The mixture wee drawn froa- this reservoir at a constant flow rate through a 27 ca^ cylindrical photolysis cell irradiated with 330 - 3S0 na light from a mercury arc source* The concentrations of HO, H02 and HH02 at the Inlet and outlet of the cell were measured and the rates of formation of HO and H02 (n^q and ^q2) k* tho photolysis determined* Successive aliquots of vinyl chloride (or other olefins) were then added to the mixture and the effect of increasing olefin, concentration on R^a and determined* The maximum extent of photolysis of HN02 was approximately 4?$* (b) Results- riff. 4 shows the effect of added vinyl chloride on the rates of NO, NO^ end total HO 4- NO2 formation in the photolysis of HH02 The rates are normalised to- unit HN02 concentration. It will be seen that the addition of increasing amounts of vinyl chloride leads to a fall in the rate of HO formation, an inorease la the rate of H02 formation and a less pronounced decrease in the total rate *W-+ N02` 5inillGr offsot* vere also obtained for the hydrocarbons ethylene* propylene and trans-2-butene. The mechanistic interpretation of the results in Fig* 4 is complex and subject to considerable uncertainty* However* on the basis of the following * simplified scheme, the data can give an estimate of the relative reactivity of the added hydrocarbon*; with OH* In the absence of additive the photolysis of BN02 proceeds by HHOa OH + NO OH +. HN02 - H20 + H02 (l) (2) Thus equal rates of HO and N02 formation are expected in the photolysis. The alightly lover rata of H02 formation with zero 0^5^01 shown in Fig* 4 is due to the side reaction of N02 with OH to give HHOj which was not measured* Vhen & compound, R, is present which reacts with 03 radicals, reaction (?) then competes with reaction (2), e# AP00018363 * K. 4* fre radical product P {3) free radical product from {3} reacts with; molecular oxygen which is present in great excess to yield poroxy radical which can oxidise NO to N02 (f)<52 < NO no2 + (P)6 Some of the (p)G radicals nay then he lost fey recombination or undergo further reactions leading to the formation of NOg. Soma of the (P)<32 radicals may also be lost fey recombination* The radical loaa processes are reflected in the decline in the total rate ^ with inoreaeing additive (Fig. 4}* In the simple oaae of R m C0r then (p)02 and (p)6 are E>2 and OH respectively and It has been shova^ that the above mechanism fita the observations for the photolysis of HNOg-CO mixtures* Furtheraore, the relative rate constants for OH reaction can be obtained from a plot of the equations Aho + A(H0 + N02> k3[R] x3 ~^(H0 + N02) kJ-N0*I kZ t?0*] where 6^ and + NO ) raPreson* th* differeneea between the RW0/HNO2'] and Rjjq + N0^/(hN023 values respectively in the absence and presence of additive, 01 io the dissociation rate of HN02, kg and kj are the rate constants for reactions (2) * and (3) respectively*and N0J [no + H0a + HN02]*. Fig. 9 'show a plot of tha data for vinyl chloride, C^, C^Hg and t-C^ff0-2 according to equation (i). The slopes of tha plots give a measure of the ratio k^/kg* l'e* the relative * reactivity of the hydrocarbons with OH* The order of reactivity is the same as that found in tha photo-oxidation experiments* By using the value of kg previously determined''',' relative to the well known rate constant for the reaction of OH with CO, values of of 9*4- x 10-12 and 5.6 x 1(fl* in t3r molecule-1 s-f un^its are derived for and CgH^Cl respectively from the above slopes* Recent determinations of the absolute value of the rate constant for the reaction of OH with ethylene all lie in the region of 3 x 1(Tia cm? molecule"* ^ \ The apparently higher value obtained in the present analysis almost certainly arises because more than one NO molecule is oxidised in the reactions following the attack of OH on CgH^* i comparison of *k,, is * n*<WI XV m. >4_ APOOO18364 . the valuer indicates s stoichiometry factor or about J. The stoiohiometry factor for vinyl' chloride la unknown and therefore the rate constant value obtained can only be regarded as an upper Unit, By analogy with ethylene the true value is probably a factor of 2 - 3 lower than the value given* 4* -Coffiparieon of Reactivity Data with Other Investigators Table XI shows a comparison of the relative re&otivlties of the substances under consideration with those obtained by other investigators vhioh have been summarised by Altshuller and Bufalini^. The OH reactivity data are compared with those of Morris- and Hiki^. # Thero is reasonably good agreement between the relative reactivities cf the various substances based on A, the rate of KO oxidation and <B the consumption of reactants The differences which are observed can. probably ba attributed i to ths different experimental conditions and measurement methods used is thsf various investigations* A close correspondence between relative reactivity *" toward OH and reactivity, in the photochemical oxidation system is also evident* This correspondence has also been noted by Morris and Hiiei On' the basis`of their OH- reaction'measurements, with'which the present e* estimates show good agreement considering the uncertainty in the stoichiometry mentioned above* It is also of interest to nota that the reactivity of trlchlorethyleno is similar to that of vinyl chloride and ethylene* 5* Products of Vlnvi Chloride Photo-oxidation In ths present: study- no Investigation of the products of the photo-oxidation of vinyl chioxlda has-been made* The nature of the expected Tftajor produota may be deduced by analogy with ethyleno for which ths major products are formaldehyde, CO and C02* Thus fission of the C-C bond occurs in the oxidation reaction, and in addition to the other three products observed for vinyl chloride would be expected to yield formyl chloride* Although formyl chloride has apparently never been isolated as a stable compound, it may be stable at very low concentrations %, -T- AP00018365 la air* ffonaally it decomposes to BCX and. CO which, will undergo furtheroxidation, only slowly in the photochemical system* 6* Eye Irritation While there is a strong correlation between the various chemical parameters used to characterise the reactivity of hydrocarbons in tha photochemical system* no such correlation exists with the eye irritation index^. This is no doubt duo to the widely differing lachrymatory effects of the produets formed from quite similar starting materials. In the absence of experimental data* any attempt to assess the eye irritation index for vinyl chloride must therefore be largely speculative* The only chlorinated compound for which the eye irritation index has been reported is trichloro-ethylene^ and there is unfortunately some conflict between two separate investigations* Trichloro-ethylene lies between propylene and. ethylene in photochemical reactivity and gives an eye-irritation Index reported to bo either somewhat greater than propylene^ or somewhat less than ethylene^* Taking the more pessimistic value* thought to be more realistic because of the possible formation of the strongly lachrymatory compounds phosgene and formyl chloride (the latter also being a potential product of vinyl chloride}* and * taking into account the somewhat lower photo-reactivity of vinyl chloride observed in the present investigation* then the data suggests that the eye-irritation index for vinyl chloride should be similar to. that for propylene* Heuss and Glasson(v2}' reported valuer of 0*3* 0*5* t*2 and 7,0 for ethylsno* trana-2-tutene* propylene and 1 *3-butadiene respectively* together with those for many other hydrocarbons* The eye--irritation warn assessed by a panel after 4 mins* exposure oss^ none* light* moderate or severe and assigned numerical values of 0* 1 * 2 and 7 respectively* It should be pointed out* however* that atmospheric measurements of eye Irritants are almost an order of magnitude lower than laboratory concentra-- frr) , tlons resulting in equal eye-irritation, according to Schuck and Doyle and there is much uncertainty surrounding the subject* . - a - AP00018566 Conclusions The results. discussed above show that (a) Vinyl chloride undergoes photo-oxidation in a similar manner to other hydrocarbon compounds when C^H^Cl-HO-air mixtures are exposed to tfV radiation of wavelength and intensity similar to that of solar radiation near the earth'a surface* (b) Tho photochemical reactivity of vinyl chloride, as measured from a ' number of rate parameters in the photo-oxidation reaction and also from its reactivity toward OH radicals, is similar to or slightly less than ethylene* Vinyl chloride la, therefore, only a moderately reactive precursor to photochemical cutoff* being leas reactive than propylene _ and higher olefins, but mors reactivs than the normal paraffins* (c) she rate constant for the reaction of OH with vinyl chloride has aiw uoner limit of *?.6 x 10*"^ cm? molecule ^ a ^ at ^00^* The true value is probably a factor of 2 - J lover than this* * ** * 9- APOObl8367 8*. Reference? 1, A.F. Altahullor and J.y. Bufalini, 'Photochemical Aspects of Air Pollutionr A Reviow*, Environ; Sol. and Tech. 39 - 64 (1971)* 2 J.H. Heuss and. V.A* Glasson, 'Hydrocarbon Reactivity and Eye Irritation', Environ* Soi. and Tech. 2, 1109 - 1116 (1968).. 5* R*l. Cox* to he published in J* Photochemistry* f* E.D* Morris and H*. Niki. 'Reactivity of Hydroxyl Radicals with Olefins'* J. Phys. Chen* 3640 - 3641 (1971). 3* S.I Kopceynskl, unpublished results (1968) reported la Ref* 1 p. 43. 6. JC.V. Vllson* C.J. Doyle* D.A. Hansen and R.D. Englert, Symposium of ACS Division of Organic Coating and Plastic Chemistry, Hew Toxic, Sept* 1969. See also Environ. Sol. and Tech. 2 696 (1969) and ibid p. 1224 together with Ref* 1 p. 43. 7* E.A. Sohuck and G.J* Doyle, *Photo~oridation of Hydrocarbons in fixtures Containing Oxides of Nitrogen and Sulphur Dioxide1, Report No* 29, Air Pollution Foundation, San Marino, Calif. (1939) see also Ref* 1 p* 56. 4 -10 - APOOO18368  TABLE y - . Rate naraaetora_in photo--oxidation of vinyl chloride anti noma fiyrfjyocB'rhnrjiy Reactant A * 4 frolfo (ppn/min. z 102) a reactant consumed after 4 hours 0 (dfO^dt)mar (ppm/min x 102) a final fp3*J (ppm) Vinyl Chloride Ethylene Propylene Trans-2-trutena 0.3f 0.34 1.40 3.0 15 25 . 83 (15)* >100 (75)* >0.017?* a >0,17* 0.53 3.75 0.60 (1300 min)* 0.47 (1300 min) 0.66 (240 min) 0-7*.. (80 min) hydrocarbon consumed after 30 minutes / maximum rate not achieved during reaction time used ** time at vhicb final ozone* oonoentration measured. l t l I. \ \ AP00018369 0Z8J000dV - z\ - . -VAS:-"aL.-=Ss: - - . . fe>' ;; . .- ^pm ** *ee sro '1 - *T nopiA V 5*0 9 - Ll'Q o* Apvt* 0TlTAT4eH* i I3H*0 51*0 52*0 TO^O z*t . 9 ^ . z 0*1 1*0 BO 0 /t,yprTK ^ofa-to;* 0*1 0*1 ro f0 Txo^dtxmsuoo vo^^ppco ^tn^ovajc OK SV V aeiimmiY 0*5 ^ o*t 62*0 SO 0 8*5 vz 2-eBV0**^ 0*1 0*1 9bo 82*0 52*0 vo'ft&sheuoa pxo^oeex `UOTVW* OK aT *ZOA TO Vo *KOTlViT;=wij X'eof^ouooio^a' Acutes ii aiavj; Tig* I Concentration tin* cuxvos for tho photo-exi'iatlon of vinyl chlori'lo in thv proaaaco of 1*0- CONU'-NTRinON 2! ( P f ^ - 15 - APOOO18371 PlC Z Plota shoving the removal o f oleH n ( f i l l e d poi-ila) and SO (open points) th ririj; the th o U -e x iia tio n of In yl chloride ( c ) f ethylene (A)V p ro ;/lo n e () and concentration axis f e r each hydrocarbon in s h ifte d tra ra -? -kttcno so th a t (0 ) , the' iinn i tthi ao l presence o f SO, The KO concentrations correspond tp 0*97 ppa 30. \ - -i APOOOI8372 001 rWU. o z o n e CotKC'JTftATtoNo * (p p TM ) Tiff, 5 Okcr* forcatiorr during tha photo-oxidation, of hydrocarbons and vinyl chlorii (filled points). AP000I8373 rig. 4 j I* The effect of _~ed vinyl chloride on the photc jaociation of nitrous acid. The plat shove the ratos of formation of KO and NOg (Rjjq and and_the totaX rata B;;o+N02* exPressd per unit HNO2 concentration aa a function of the concentration ratio (^HjCiJ/JeXOj]* Rftrs/ [fcNO^ CsccT1a10?O - 16 - AP00018374 S48lOOOdV - 41 90 -h-V Ofi\ (7) U074.VT&* * 9u?pjo09 oo^n^xps TJto-20*H jo tcvCx 0*0:0 oy* eo*; 9*op oiw oij; jro *otI S ks viNYt.au OKI!** iirtAKt sir mu i;ium A HI Milter, K. G. 19GS. Siawtianeuus wotistfcet McTrncr, Toronto: McGraw-Hill. SUuumeno,. O. I'M t. Ahtuiptiun, fate end excretion <il vinyl chloride. AIM VJmhk fl.cwtbmea, Gtr.) 7ilX>-\47. Thomas/ U 0., Popper, II., [fctk, P. O., Sclikolf, I, |. and Falk, it. 19751 Vinyl chloride induced liver diwaee. N. /. A/rd 292; 17-22. Hanir, N. It. and Culruwi, \. I*. 19/2. I.ctiuirv nit the analysis anti imrrpreuiion til cell ifccigne with, unequal ceil frequencies. College of education, University of Pittsburgh, I'cnnsylvanu. vad. Etch, G. J. and van tegten, M. J. 1975. Vinyl chloride; A report of a European assessment. Food Cofmet. Toxicol. 13:121-139.- VloU, P. z., Bigotii, A. and Capulo, A. 1971. Oncogenic response of rat skin, tungfrand bones to vinyl Chloride. Grocer Ret. 31:516-522. Wagner, J. G. 1971. Biopharmactutia. and Relevant Pharmecohl/retict, chape 25. Hamilton, Illinois: Drug Intelligence Publication*. Williams, D. T. and Mifcs, W. F. 1975. Gas-liquid chromatographic determination of vinyl chloride in alcoholic beverages, vegetable oil* and vinegar*. /. Attoe. Oftie. Anot. Cheat. 56:272-2751 Wlthey, ft, 7.1976. The pharmacodynamic* and upuke of vinyl eWorld* monomer administered by various routes to rats. /. ToxIcoL Environ. Health 1:3tl-394 Received Apr# 7, J97S Accepted July 14, 7975 *: * i *. 4. g t. nnOt s gfSKHESs.. a.T s e_ . r a. r TT. i. AP00018376 MANUFACTURING CHEMISTS ASSOCIATION t8?b CONNECTICUT AVENUE, N.W. WASHINGTON, O.C. 2000G (?02f 483'GI2G April 26, 1977 NiiotlVEO^ RESEARCH & DEVEUOPMENK APR 2 8 1977 W. M. SMITH TOt Vinyl Chloride Technical Panel SUBJECTS A. Statistical Assessment of the Quantitative Uptake of Vinyl Chloride Monomer from Aqueous Solution Gentlemens Because of ita relevancy to research currently in prog ress the attached subject paper is being made available to all**. Panel members. ^ JTSsce.. 'z&l Attachments -c, T. Seawell Project Manager Vinyl Chloride Research APOObi8377