Document bBapVnYGy6KwjLG8nEX7BL8Ek

1 nnical PubL >, ;nrfiowjc. u,( Med.,63, l))j I* the lung, fir ; - i of v-italliutn t menean Eliey*. g in conjunct^ he tibia, Cantr 51. ,9,95.1963. O' CHEMICAL REACTIVITY, BIOTRANSFORMATION. AND TOXICITY OF POLYCHLORINATED ALIPHATIC COMPOUNDS Authors: C. Bonse D. Henschler Institute of Toxicology University ofWurzburg Wurzburg. Germany Keferee: Perry J. Gehnng Toncoloiy Reswrch Laboratory Dow Chemical Company Midland, Michigan : INTRODUCTION Chlorinated aliphatic compounds are released, increasing number and quantity, into the sfironment. They are used on a large-scale basis s industrial solvents, in textile cleaning shops, and seal* plastic monomers, pesticides, and drugs. Some / the technically important products have long known as hepatotoxic agents, and single ati. limbers of the family (like vinyl chloride and e. aylidene chloride) have recently been claimed to carcinogenic: at present, trichloroethylene is 1. i suspected as a potential carcinogen. In usr idition, several polychlorinated compounds usess a marked persistence in biological and ,6, 173, 1972, ilymers foi un-i aotic systems and may accumulate to health- ueatening concentrations. lent of lysosotL, The means and degree of metabolic transforma nt of chlorinated compounds, which may vary Jumore), 7,10!"l xmderably, are influenced to a great extent by x nature of the chlorine substitution of differ- yf methods. f*. % hybridized C-stoms. The tendency of the Aivior of the compounds under consideration > sosomal enzy tth respect to metabolic and nonmetaboiic activity can be particularly well demonstrated ith poly- and perchlorosubstitutions. This report Z>.,9,9.19 scribes some aspects of the interrelationship among polychlorinated aliphatics, chlorine substi tution, chemical reactivity, and metabolic fate in biological systems, as well as their toxic properties. The molecular context is emphasized, whereas details of enzyme mechanisms and pathophysio logical aspects of toxic reactions are not dealt with. GENERAL CONSIDERATIONS ON CHLORINE SUBSTITUTION IN ALIPHATIC HYDROCARBONS In general, chlorine substitution provides a decrease in the electron density of the involved C-atoms by their electron-attracting inductive effect (-1 effect) which dominates the mesomeric donator effect. In nuclear magnetic resonance spectroscopy, the frequency of the resonance of an atomic nucleus depends on the electron density of its environment. The diamagnetic protection by the electrons diminishes the effective magnetic field at the nucleus. Thus, the shift of the resonance absorption may serve as a criterion for the electronic influence of substituents.1 Recent publications3'* reveal the possibility of a linear correlation between 13C-NMR shifts and the total electron density of the corresponding C-atoms. ' SL 066528 Thus, the position of the 13C-NMR signals is a measure of the electron-attracting effect of chlorine subsututions in organic molecules. The electronic shifts indicated in Table 1 clearly illustrate that an increase in chlorine substitution induces a decrease in electron density at the substituted C-atom; this correlates with a shift of resonance signals to lower fields. Substitution of hydrogen by chlorine in alkenes results in a smaller shift of 13 C-signals than it does in alkanes. This is probably due to the interaction of the chlorine with the ir-bond. The inductive effect may be dominant in chlorinated alkanes, but in alkenes another effect (magnetic anisotropy, resonance effect) may contribute to the shift.* The mesomenc substitution effect encountered with chlorine substituents may also be demon strated separately by microwave and radiowave spectroscopy.*'10 One criterion of the mesomenc effect is the bond extension C-Cl which will be submitted in part to some kind of "double-bond character" and thus to a contraction by the participation of zwitter ionic structures. Thus, for example, the bond extension C--Cl is 1.76 A with alkanes, 1.69 A with alkenes (e.g., vinyl chloride), and 1.63 A with alkynes (e.g., chloroacetylene). The proportion of the double-bond character of the C--Cl bond, according to nuclear quadmpole measurements, amounts to 5 to 6% in the case of vinyl chloride. An enforced electron-attracting effect in connection with steric factors resulting from polychloro- or perchlorosubstitution induces decisive changes in reactivity as compared to TABLIi l 1 *C-NMR Shifts of Qiloiinated Aliphatic Hydrocarbons (ppm Referring to CS, * 0 ppm)4'1 c, c, c, c, CH, CHjCl cH.a, chci, CCl, 194.9 167.7 138.6 115.6 96.8 CH, -CH, CH,C1--CH, ciia, -ch, CQ, -CH, CCl, -CCl, CH, =CH, CHC1=CH, cci,*ch. tt*n*CHCl-CHa ciiCHa=CHCl ca.sCHa ca, =cci. 186.9 151.9 123.6 96.9 87.3 70.0 66,7 64.1 71.7 73.5 67.8 72.1 186.9 174.1 160.3 146.5 87.3 70.0 75.4 77.3 71.7 73.5 75.3 72.1 unsubstituted hydrocarbons. In the series 4 sions of alkanes, an increasing chlorine substitution with t focused elongation of the carbon chain results in x homdogues enhanced tendency toward destabilization, whid 1 been inclu leads to C-C fission^ or eliminations of HQ oi, chlorinate chlorine with consequent formation of alkenes. Ot ' convertet the other hand, alkenes are stabilized against ( COj,15 ch Jelectrophilic agents by increasing chlorine substitu- j methane t- tion; chlorinated olefines are characterized by n A dee: elevated thermal stability. Alkynes, unlike alkenes ' henatotoxii are considerably destabilized by chlorine substitu- edin 1961 1 tion- ALKANES v C-Cl fiss . 1 methyl ar " probable mechanism a methyl ra with the ; - -c --c -- II radical. Thf peroxides induce t` The destabilizing effect in chlorinated alkanes it chains.16 observed with an increase in the number of chlorine and carbon atoms. The steric hindrance ~ accumulated chlorine substituents, as well as u-- electron-attracting effect, favors C--C fissions (s. structure below) and eliminations of G2 or HO with the formation of more stable olefine compounds (b, structure below). Carbon Cl Cl II -C--C -- -- C -C -- < (b) \ C: / / c \ substrate microsom reactions ra. .i I The compu For example, thermal decomposition of & cachlorobutane (1) renders, by C--C fissw thetrachloroethylene (2) and hexachloroethas* (3). Under dechlorinating conditions, hexachJw^ butadiene (4) may easily be obtained fro"1 decachlorobutane (l).11 .- decompos chloroform The wor esiabltshei C-CI fissi the orgarusr Dyke and involved s CCl, -CCl, -CO, -cci u) cn,-cct, +co,-txJ> (J) (3> CCL-CC1- CO-CCk I > I function c and benzo h'ADPH.:' found wit chlorinate C-A Fission ' Up to now, investigations on metabolic cofl**r (CHClj (CHClj-C (CHClj-C 396 CRC Critical Reviews ui Toxuvluxy SL 066529 In the series of ibstitution with s ain results in e tabiiization. whict nations of HQ ion of alkenes. Og stabilized agains ; chlorine substita haracterized by to res, unlike alkenes, chlorine substitu- lorinated alkanes is 1 the number 'of steric hindrance of its, as well as their s C-C fissions (a, ons of Cl5 or HQ re stable oleftnk sons of chlorinated aliphatic hydrocarbons have focused on Ci and C3 compounds; higher homoiogues of C3 and C4 units have occasionally been included. Regarding the Ci series (the chlorinated methanes), carbon tetrachloride is converted metabolically to chloroform and CCL,13 chloroform to C03,15 and dichloromethane to CO.14 A deeper insight into the mechanism of the bepatotoxicity of carbon tetrachloride was provid ed m 1961 by Butler1 s who suggested a homolytic C--Cl fission with the formation of trichloromethyi and chlorine radicals. At present, the most probable subsequent pathochemical reaction mechanism is the interaction of the trichloromethyl radical with unsaturated fatty acid chains, with the formation of chloroform and a fatty acid adieal. The latter reacts with oxygen and forms peroxides and hydroperoxides which, in turn, induce the decomposition of the fatty acid chains.16 At the same time, it was recently demonstrated that the hepatotoxic activity of Cl a--/ \ a a / , cic \ a Carbon tetrachloride forms an enzymesubstrate complex with cytochrome P4J0 of liver microsomes30 in which the following sequence of reactions takes place.31 CCI. + ie CO, +16 --CC1, + 1C19 1CCI,9 The complex cytochrome P4So-ICCljd may then decompose in the presence of protons, releasing nposition of de- chloroform as the stable final product. by C--C fission, * The work of Heppel and Porterfield33 has well hexachloroethanc 1 established that enzymes catalyze the oxidative itions, hexachloro- C-Q flasion of chlorinated organic compounds m >e obtained from the organism. According to Van Dyke 33 and Van Dyke and Chenoweth,34 the enzyme system involved shares all relevant properties with mixed n, -cci, + ca, -cci, , function oxidases. It is inducible by phenobarbital (2) (i) , I end benzo-a-pyrene and requires oxygen and CLCCI - CC1-CC1, Ml NADPH.3 * High rates of dechlorination have been found with this enzyme system in the series of chlorinated ethanes: 1,1-dichloroethanes fCHCl3 -- C H 5), 1 ,1 ,2*trichloroe thane (CHClj --CH3C1), and 1,1,2,2-tetrachloroethane 1 metabolic conver- (CHQj --CHClj). Ethanes with a trichloromethyl bromotrichloromethane (BrCClj) is considerably greater than that of CG4 or CHQj.17 There is a correlation between the cytotoxic effects produc ed in vitro and in vivo and the bond-dissociation energies for the fission of the three methane derivatives (CHQj, CCU, and B1CCI3): H-CClj, 95.7 kcal/mol; Cl-CClj, 73 kcal/mol; Br-CCl3, 54 kcal/mpl.1 ,'1* A low dissociation energy corresponds to an increased tendency for a homolytic fission to the trichloromethyl radical. Correspondingly. BrCOj is considerably more effective than CCU in producing a peroxidative breakdown of the microsomal lipids in rat liver.17 In principle, chlorine-substituted alkanes tend to have radical reaction mechanisms because chlorine substituents are capable of delocalizing the unpaired electron via empty d orbitals of low energy. Consequently, the resonance energy of the CClj radical amounts to 8.3 kcal/mol (as compar ed to the CHj radical = 0). Possible resonance structures of the trichloromethyl radical are shown below. a a. (CClj-) group [for example, 1.1,1-trichloroe thane (CGj--CH}|. 1,1,1,2-tetrachloroethane (CClj--CH5CI), and 1,1,1,2,2-pentachloroethane (CClj--CHGa)] are characterized by a low ten dency towards oxidative dechlorination; the same is true for tetrachloroethylene (CC13--CC13). Accordingly, acute and chronic hepatotoxictty are high in the former and low in the latter group of chlorinated aliphatics.36*31 Elimination of Chlorine The elimination of cblonne with formation of more stable alkenes represents the second type of metabolic conversion of chlorinated alkanes. This is the main pathway and the first step in the metabolic conversion of pentachloroethane (5)39 and hexachloroethane (6),30 leading to the formation of trichloroethylene (7) or tetrachloroethylene (2), respectively. CHCl, -CCI, -CL CHC1=CCI, (S) (7) CCI,-CD, te) -ci2-+. cci, *cci, (2) October 1976 397 SL 066530 However, an analogous mechanism with 1.1,2.2-tetrachloroethane (8) which would yield !.2-dichloroethylene (9) could not be demon strated up to now. The predominant pathway m the metabolism of 1,1,2.2-tetrachloroethane (8) goes through the sequence dichloroacetaldehydedichloroacetic acid (10-11), while the product of nonenzymatic dehydrocholorination (b) is found only in minor proportion; this reaction is already found in neutral phosphate buffer.'*1 In addition, traces of oxidatively formed tetrachloroethylene (2) are found. CHC1-CHC1 <> )( CCT,-CCt, 4(21 CHCt, -CHC1, () . [CHC1,-CH0| do) CHG-CC1, n) CHCL, -COOH J (It) CO, Eliminatiun of HC1 The elimination of hydrogen chloride from polychlorinated alkanes, leading to olefinic structures, also represents a major pathway in the metabolism of p.p'-dichlorodiphenyltnchloroethane (DDT) (12), with p.p'-dichlorodiphenyldichloroethvlene (DDE) (13) as the first metabo lite.33 This conversion is additionally catalyzed by the enzyme "DDT-dehydrochlorinase" (E.C. 4.5.1.].) m the presence of glutathione.33 (12) (12) Dehydrochlorinations are also discussed as primary metabolic pathways of polychlorinated cyclic alkanes, for example as in the case of 1.2,3,4,5,6-hexachlorocyclohexane.34'35 The 7-isomer of C4HAC16 (14) is convened, by successive dehydrochlonnation, via a 7-pentachlorocydohexene to 1,2,4-mchJorobenzene (15). 398 CAtC Critical Ncvuns in Toxicology which is then conjugated after aromatic hydroxyl^ convert hexachloi ation.3 s maleic acid anhydr ct -3 HO HH CT (H) )! H (11) ALKENES. Cycloocto terrene a \c=c s /\ 1 representative of s' | nating double bor i oxygen. After an ex *s heating, it converts resinous substanc. Considerations on Stability * the molecule is Poly- and perchlorosubstitution at sp5 -hybrid addition of halogt ized C-atoms in unsaturated systems increases the | (O;, KMnO*, and ' thermal and chemical stability of these molecules. j with ring contrat The -I effect dominates the +M effect of the , ! chlorocylooctatetre chlorine substituents, thus resulting in a "depriva-11 octatetrene (20) c tion" of the electron density of the double-bond thermal and cher system. This provides, in combination with a steric protective effect of the bulky chlorine substitu- . the pressure tube cydooctatetrene , ents, an increased stability against electrophilic With elemental b^ attack. the composition C A good example of this effect is the reaction of octatetrene (20) chlorinated ethylenes with ozone. The relative , aqueous KMnO* rates of ozonization in the series ethyleneivinyl- under varying cc chloride:trichloroethylene:tetrachloroethylene are 2500:1180:3.6:1.36 ' I stable up to 18 ^ remarkable inertne: ! be determined in t. CH, =CH-CH=CH, (16) CC1, =CC1-CC1=CC1, (17) | laied voluminous . render an electron * their -1 effect. The Liquid butadiene (16) (bptto -5.6 C) poly merizes when left open to air for months after some period of induction; light irradiation acceler ates the reaction. On the other hand, hexachloro- 1 of an extraord systems by poly- . be further demons I (Table 2). butadiene (17) (bpt40 213C) is stable up to 500C and cannot be brought to polymerization by pressure up to 100 atm (17), in addition, is characterized by a remarkable chemical stability, similar to the higher homologous stereoisomeric perchlorohexatrienes.3' They are fairly Stable against strong mineral acids and aqueous alkali even at high temperatures, but are converted to highly chlorinated vinyl ethers by alcoholic alkali Metabolism Chlorinated I converted to pred ' A significant mt | strated between u j with increasing m. I and the metabo [ with all chlorin at 80C.3* At least the action of fuming nitric acid at 130s and additional treatment with concentrated sulfunc acid at 170 are necessary to SL 066531 'matic hydroxyl- ,-onvert hexachlorobutadiene (17) to dichloromaleic acid anhydride.' * ci a 1 Cyclooctotetrene (18) (bp-rS0 1414C), a representative of cyclic polyolefines with alter nating double bonds, is sensitive against light and oxygen. After an extended stay, or acceleration by beating, it converts to a mixture of dimers and resinous substances. The enormous reactivity of the molecule is again demonstrated by the rapid n at sp5-hybrid-* ms increases the' these molecules. | \1 effect of the' lg in a "depnva- j the double-bond .ion with a steric 1 hlorine substitu- ' nst electrophilic addition of halogens.40'41 Attack of oxidants 10;, KMnO, and CrOj) easily results in products wth ring contraction. The transition to pemachlorocylooctatetrene (19) and octachlorocydoocutetrene (20) coincides with an increase in thermal and chemical stability. After heating m the pressure tube for 6 hr at 250C, pentachlorocyciooctatetrene (19) can be isolated unchanged. With elemental bromine it reacts to a product of the composition C|H3ClsBr:.42 Octachlorocyclo- .s the reaction of ie. The relative ' , ethylenetvinyl- ' .oroethylent are' octatetrene (20) does not react with ozone or aqueous KMnO* and cannot be brominated under varying conditions. It remains thermically ruble up to 180C.4 3 ,44 The reason for this remarkable inertness of the double bonds should be determined in the protection by the accumu =ca-cci=cci; lated voluminous chlorine atoms which, per se, render an electrophilic attack more difficult due to (17) their -1 effect. The validity of the general principle , -5.6'C) polyor months after adiation acceler.nd, hexachloro- of an extraordinary stabilization of olefinic systems by poly- and perchlorosubstitution may be further demonstrated by some paired examples (Table 2). is stable up to polymerization . in addition, is emical stability, i stereoisomeric e fairly stable aqueous alkali re converted to alcoholic alkali Metabolism Chlorinated ethylene: are metabolically convened to predominantly C3 alcohols and acids. A significant interrelationship has been demon strated between the enhanced stability associated *ith increasing numbers of chlorine substitutions and the metabolic behavior in biologic systems wnh all chlorinated ethylenes in the isolated >f fuming nitnc reatment with are necessary to perfused rat liver preparation.*1 ,s 2 At a given prehepatic concentration of the ethylenes, a significant rise in the proportion metabolized was found in the series tetra-, tri-, and cis-1,2-dichloroethylene vmyiidene chloride. The metabolic changes of chlonnated ethylenes are initiated with the oxidation to corresponding oxiranes5'**6 by monooxygenases. Up to now this class of compounds has only found limited interest. The principal reactions of oxiranes in biological systems are summarized in Figure 1. The main toxic effects, acute as well as chronic, have been associated with electrophilic reactions with essential cellular components (alkylation), whereas the other pathways (reduction, hydrolysis, and conjugation, both enzymatically and nonenzymatieally) and rearrangements of earbonylic com pounds are considered to be detoxication mechanisms. The type of rearrangement in chlori nated ethylenes depends on the number and position of chlorine substitutions); it goes to either chlorinated aldehydes or acyl chlorides. \/ cc /\ G RiH.Cl A c--c /\ Cl a c -- Further metabolic steps with the rearrangement products are oxidations or reductions of aldehydes to carboxylic acids of ethanol derivatives or hydrolyses of acyl chlorides to corresponding acids. With tetrachloroethyleite (2). the metabolic formation of trichloroacetic acid (23) can plausibly be explained by the primary' formation of an oxirane (21) and subsequent rearrangement to tnchloroacetyl chloride (22) and its hydroly sis* 2,4i The transition of the oxirane to trichloroacery! chloride (21 to 22) is, in analogy, found with the tetrachloroethylene oxide (2) which can be synthesized by photooxidation and which rearranges in vitro in different solvents to trichloroacetyl chloride.*1 October 1976 399 a SL 066532 TABLE 2 Companion of the Stability of Uraubstilulcd and Pcrehlorosubstiiuted Cyclic Polyolefines Bicyclo-14,2,0) oetatrien-O J.7); some hours stable at room temperature, rapid poly merization at open air Stable at room temperature, no tendency to polymerization, rearranges to aromatic com pounds at B0`C Cl 3,4-Dintethylenecyclobutenc; rapid polymentation in the presence of light and air Stable in air up to 160*C ^J FIGl , (all 1 Trichloroethvl ed to trichloro*' converted to c ' metabolic react, to trichloroetha: acetic acid (2. oxirane (24) as substantiated by | the catalytic het I enzyme tnonoo . After admir.. I ethylene to ex activity rental 1 metabolites tr 400 Utc Critical Reviews m Tuxuolum SL 066533 / CC1, -- c \ OH (23) TABLE 2 (continued) Compuiton of the Stability of Uneubitituted end Pcrchlorocubsuruted Cyclic Polyolefines HH Cl Cl (49) ($0) lyoiefincs 46) tendency to imauc com- (48) T*1 11 rv V C5 ( if* i .m - t Heptafulvene: polymaizauon in jolution aiieady it *80* C Stable m eir up to 340*C reaction with galtuler macromoiwMilOT (alkyiation) BOniupetton (glutathione) \ / -o-x-i-d-a-t-i-o-n-- C c* / \ roduction hydroiyeie V OH OH rearrangement --C e-- FIGURE I. Synopsis of metabolic conversions and biological consequences of toxication (alkylation) and detoxication (conjugations, hydrolysis, and rearrangement) of alkenes. I Trichloroethylene (7) is metabolically convert ed to trichloroethylene oxide (24) and further converted to chloral.*3-1** *'*9 In subsequent metabolic reactions, chloral (25) is in part reduced to trichioroethanol (26) or oxidized to trichloro acetic acid (23).40 The real occurrence of the oxirane (24) as a metabolic intermediate could be ' substantiated by spectroscopic investigations with i the catalytic hemoprotein P< J0 of the converting j enzyme monooxygenase.41 After administration of 34 Cl-labeled trichloro ethylene to experimental animals, the specific activity remains unchanged in the recovered metabolites tnchloroethanol and trichloroacetic acid; no exchange of 14 Cl with the chlorine pool of the organism is observed.*3 Again, this is indicative of an 'intramolecular chlorine migration in the course of the transition of trichloroethylene oxide to chloral (24 to 25). Surprisingly, at first glance, the trichloroethylene oxide (24) which can be synthesized from trichloroethylene by photo chemical oxidation45 thermally rearranges (in vitro) mainly to dichloroacetyl chloride (27).4 3 In vivo, however, no dichloroacetic acid is found as a metabolite.*5'44 This remarkable difference has important practical implications. In principle, there are three potable ways of rearranging the oxirane of trichloroethylene (24). OctobeT 1976 401 SL 066534 a ,,-^c -- c { /V" \a V ci > C1 U) CHCL -- C \ Cl a fo ( (2) C--C'-' / \l Cl Cl a \/ C=C /\ HH (28) /CK\ Cl '''"-* Cl' C3> CC1,-- c \ Cl h Regarding the two rearrangements leading to dichloroacetylchloride, the hydride shift (2) has low probability, according to investigations by McDonald and Schwab.*s If one postulates that o-ketocarbonium ions or ion pairs6***! are transi tion forms of the rearrangement (a synchronous process cannot, however, positively be ruled f'ut*9), the earbonium ion (which after C--0 heterolysis is solely destabilized by one direct, liganded Q atom) should be indicative of a favored rearrangement. Way (3) would involve a earbonium ion with two direct liganded Cl atoms, consequently giving a lower degree of probability. Experiments on the behavior of the oxirane are in accordance with this assumption: rearrangement to Lewi: acid ewis acids is an interaction with the oxirane (24) t the site where there is a steric opening of the rolecuie with the oxirane oxygen, with the dichloroacetyl chloride is accelerated by tertiary amines70 which, after addition of methanol, render dichloroacetic acid methyl ester.71 Upon heating to 100 to 140C for 4 hr in a glass tube, the oxirane is convened in high yields (88%) into dichloroacetylchloride. and only a small proportion of chloral can be detected.*9 The rearrangement of trichloroethylene oxirane to chloral in vitro can only be elicited by Lewis acids suchasAlClj or FeG$.55 Thus,it has been suggested that in the living organism the "environment" at the site of formation of the oxirane (24) might poss ess electron acceptor properties and induce the re arrangement in the direction of chloral.51'55 The most plausible mechanism for the influence of C -- CC13 / nearest chlorine atom, or with both, inducing the final rearrangement according to shift (3) to chloral (25). /\ HC | (29) Cis- and irons- , 29) both form the I (32) and dichloroar| identified in perft preparation.51 ,s 5 - I plained by the pnm; Cl H \ c=c / /\ Cl H (33) The isomeric 1 ' chloride) (33) ts m acid (36)"'7i If i. with m-chioroperber chloride (35) (the e of the oxirane) car seems to be extrem-. Cl \ / c=c /\ HH (37) \ 402 CMC Critical Rcvivhs in Toxicutuxy SL 066535 H/ \ cA--c / /\ HH (40) f\ \S) \ C! a Cl /\ HH (28) ccelerated by ternary dition of methanol, nethyl ester.11 Upon r 4 hr in a glass tube, ugh yields (88%) into only a small propord.43 iloroethylene oxirane elicited by Lewis acids us, it has been suggestthe "environment" at urane (24) might possies and induce the reon of chloral.51,32 n for the influence of h both, inducing the ng to shift (3) to Cl H /\ H Cl (29) GSs* and trans-1,2-dichloroethylenes (28 and 29) both form the metabolites dichloroethano! (32) and dichloroaeetic acid (11) which have been identified in perfusates of the isolated rat liver preparation.51,12 Their formation can be ex plained by the primary intermediate oxiranes (30 and 31) and subsequent rearrangement to dichloroacetaldehyde 0 0), which is then oxidized to dichloroaeetic acid (11) or reduced to dichloroethanol (32). The thermal rearrangement of the oxiranes that occurs with chlonne migration to diehloroacetaldehyde (10) has been demonstrated.44 (33) (34) The isomeric 1,1-dicMoroethylene (vinyhdenc chlonde) (33) is metabolized to monochloroacetic acid (36).44'12 If 1,1-dichloroethylene is oxidized with m-chloroperbenzoic acid, only chioroacetyl chloride (35) (the expected rearrangement product of the oxirane) can be isolated. The oxirane itself seems to be extremely unstable and resistive to /Cl \ c=c /\ H (37) \ Cl o H \/ \/ C --C /\ HH /H H \/ \/ C --C /\ HH (38) (40) CH,C1 -- C \ Cl CH,C1 _ C \ OH (35) (36) synthesis under varying conditions.13 However, from these findings it can be speculated that the oxirane (34) is formed as a metabolic intermediate and rearranges spontaneously to chioroacetyl chloride (35), which is subse quently hydrolyzed to monochloroacetic acid (36). CH,C1 -- C \ (39) CH,C1 -- C \ OH (36) October 1976 403 SL 066536 Monochloroacetic acid (36) is likewise formed as a metabolite of monochloroeihylene (vinyl chloride) (37).74'7* One possible explanation of the formation of monochloroacetic acid (36) is the primary oxidation of monochloroeihylene (37) to vinyl chloride oxirane (38), which rearranges to chloroacetaldehyde74 (33) followed by further metabolic oxidation to chloroacetic acid (36). In analogy, monochloroacetaldehyde (39) is formed as a rearrangement product of the oxirane of vinyl chloride, which can be synthesized by chlorination of ethylene oxide (40) in the gaseous phase.77'7' The further metabolic fate of vinyl chloride oxirane has been elucidated in part. A very small proportion of metabolized vinyl chloride is bound covalently to tissue components, as has been shown in vitro7* and in vivo.*0 Major metabolites in vivo are 2-hydroxyethylcysteine*1 (41), 2-hydroxyethyl-N-acetylcysteine'1 (42), carboxymethylcysteine*3 (43), and thiodiacetic acid'1(44). The mechanism of the formation of these conjugates can easily be explained by the previous rearrangement of the oxirane to chloroacetaldehyde (39) and oxidation to chloroacetic acid (36) which reacts with glutathione; carboxymethylglutathione is converted to carboxymethylcysteine (43), and the latter, by further oxi dations, is converted to thiodiacetic acid (44). Yllner has identified carboxymethylcysteme (43) and thiodiacetic acid (44) as the main meta bolites*3 in the urine of mice after dosing with chloroacetic acid. The formation of S-(2-chloroethyl)-cysteine and its N-acetyl conjugate7* as products of simple addition reactions has been questioned;*1 in fact, this hypothesis is incon sistent with an enzymatic mechanism postulated according to the results of experiments in vivo with enzyme inhibitors.74'*0 The formation of a cyclic vinyl chloride peroxide, in equilibrium with an oxirane-singlet oxygen complex, might account for the observed formation of formaldehyde as a decomposition product and oxidation to carbon dioxide, which has been identified in part, in vivo, after metabolic incorporation into urea or methionine and serine.7* Another interesting hypothesis is the addition of vinyl chlonde to hydrogen sulfide under formation of bis-(2-chloroethyl)-sulfide, which then might account for the formation of thiodiacetic acid7* (44); the alky lating intermediate could be suspected as one of the carcinogenic metabolites of vinyl chloride. However, further experiments, particularly in Iso lated biological systems, are necessary to confirm or reject these assumptions. 1 .. , ' CH,OH -- CH, -- S -- CH, -- CH -- C OH NH --C '"CH, / CH,OH-- CH, -- S-- CH, --CH --C \h (42) NH, /: CH, -- S -- CH, --CH \ HO (43) OH \/ C -- CH, -- S-- CH, -- C /\ HO (44) OH Mutagenicity and Carcinogenicity Three chlorinated ethylenes exert mutagenic effects: vinyl chloride,*4**6 vinylidene chloride,**'*7 and trichloroethylene** (see Figure 2). The common molecular feature of these compounds is the formation of unsymmetric oxiranes,* * '* * the stability of which (as tested in non polar solvents) is far less* 3 ,7 3 ,7 7 than that of the others which form symmetric oxiranes5 7'** and are not mutagenic. Oxiranes may react in vivo enzymatically or nonenzymatically with SHcompounds to form nonactive conjugates.** On the other hand, the highly electrophilic oxiranes may react directly with nucleophilic constituents of the animal cell as a first step in a genetoxic effect. If this mechanism is taken to be essential for the mutagenic effects (as has been elucidated in the case of vinyl chloride),*5 the interre lationship between symmetry/asymmetry and stability/instability of the oxiranes might offer an important rule" and possibly a useful criterion which may be used to measure chemical reactivity and predict biologic activity (see Figure 3). Vinyl chloride has been demonstrated to be carcinogenic >2 V , . 404 CR(. (.rincal Mcvti ws m Tuxuotofy SL 066537 Ct C` -200 e S E 100r l F1GURE the comp" activating different methyltryp v / H \ / H \ / *> FIG: of Fig necessary to confirm . -- CH -- C , --CH --C -- CH -- C w ^!> *11)!;:*?| ] i|fT icity nes exert mutagenic e ,*4~* * vmylidene thylene*6 (see Figure ar feature of these ion of unsymmetric jf which (as tested in t j ,i j ,7 7 than that 0f metric oxiranes*7'** anes may react m vivo matically with SHive conjugates." On electrophilic oxiranes leophilic constituents i step in a genetoxic taken to be essential s has been elucidated ride),*5 the interreitry/asvmmetry and .iranes might offer an oly a useful criterion re chemical reactivity (see Figure 3). Vinyl ed to be carcinogenic FIGURE 2. Mutagenicity of chlorinated ethylene* in an in vitro test system. Incubation of the compounds in concentrations (aqueous phase) from 0.9 to 10.9 nvW in a metabolic activating microsomal system. Results as percent of spontaneous <* 100%) mutation rate m different opetons of the test getm E. coli K,,: gal", galactose; arg , arginine; MTR , methyltryptophane; nad*, NAD.** \/ \ / C--C /\ tetrachloroethylene tridtloro- ethylene /N H \/\/ c--c /\ *.1* diehloroethyiene \/\/ l.l^iehloro\ ethylene S H \/_\/ yC ^ nenvUdiehloroethyiene 91 H gjg _ M \ /\ / c -- C vinyl dtlorlde /\ H eymmetric rel. tteble net mutegenie eeymmethc unstable mutagenic FIGURE 3. Molecular features of oxidative metabolic intermediate* (oxiranes) of chlorinated ethylenes in relation to their mutagenic potenttal m vitro (e Figure 2). October 1976 *05 SL 066538 in humans*0 and experimental animals.*1 In high Dichloroacetylene (46) is also extreme!, 14. Kubic, V. 1- oral doses, trichloroethylene produces malig nancies in mice.'3 Vinylidene chloride also has been reported as an animal carcinogen.9 3 ALKYNES -C-C-Cl In general, chlorine substitution of sphybridized C-atoms in allenes and acetylenes results in a destabilization of the molecules. This has been demonstrated with perchloroallene (45), which is stable only below -50C and starts dimerization from -30*C upward." '*s Similar behavior is encountered with tribromoallene, perbromoallene, and trichloroallenes with electronegative sub stituents.**"" Cl xci sc=c=c ci-c=c-ci ci, c*cci-cscci a' xci (45) (46) (47) reactive (explosive) and decomposes immediately in the presence of air, to phosgene and carbon monoxide.100 The destabilizing effect of chlonnt Meub, Dtspos. 15. Butler. T. C vitro by tissu 16. RecXnagel, K substitutions at sp-hybridized bonds has also been Crit. Rev. Tox, demonstrated (though in a less intensity) with 17. Koch, R. R perchlorobutenyne101 (47); this thermally un dissociation * ' IB. Kerr, J. A., E stable compound forms (slowly above Z5C) i Benson, S. W., dimer, C,C1. 1 20. McLean, A. E. The metabolic fate of chlorinated acetyl 1967. enes and allenes has not yet been investi 21. gated. Dichloroacetylene which is formed from trichloroethylene, tetrachioroethane(s), or acetyl i J*ene in some working environments produces 23. UUrich, V. a Drug Metab. L Heppel. L. A/ Biol Chen Van Dyke, F a highly characteristic symptomatology of enzymes, / t.. acute intoxication: irreversible damage to 24. Van Dyke. R the cranial nerves (predominantly the nervus methoxyflu- trigeminus) in humans103 as well as experi 25. Van Dyke. F vitro, Biochi mental animals* os"los and tubular nephro 26. Spencer, H. ( toxicity in animals.104'105 Whether these dichlonde dr' toxic effects are due to the reactive dichloro 27. Toskelson. 1 acetylene or to metabolites is open to further laboratory a experimentation. 28. Carpenter, C interpretation . 29. Yllnet, S., M 30. Fowlet. 3. S 530, 1969. 31. Yllner, S,, M 32. Hayes, W. J with difTerer 33. Agoan, M., . REFERENCES 1 1963. lK Sternbuig, J flies, / Ecor 1. Dailey, B. p, and Shooleiy, J. N-, The electron withdrawal power of substituent groups, / Am. Chem. Soc.. 77, 3$ Grover, P. L 3977, 1955. in rats, Bioche 2. Tokuhiro, T. and Fraenkel, G., Origin of linearity of carbon-13 shift with charge. Calculations for the aztnes,/4m. 36. Williamson, D Chem. Soc., 91, 5005, 1969. Am. Chem. . 3. Bloor, J. E- and Breen, L.. Valence shell calculations on polyatomic molecules. 11. CNDO 5CF calculations on 37, Roedig, A.. monosubstituted benzenes. / Phys. Chem., 72, 716, 1968. ` Triacetylen.Ii 4. Kajimoto, 0. and Fueno, T., Inverse substituent effect in the '1C chemical shifts of rnom-i-substituted-1,3- , 38 Roedig, A. and butadicncs. Direct evidence of bond polarization effected by substituents, Tetrahedron Lett., p. 3329. 1972. aus Perchlor 5. Miyijima. C-, Takahashi. K,, and Nishimoto, K., Carbon-13 nuciear magnetic resonance spectroscopy. K. 1 35 Fonch, M. i Monosubstituted ethylenes, Org, Mann. Reton., 6,413, 1974. Ber.. 106. 13-. 6. Hawkes, G. E-, Smith, R. A,, and Roberts, J. D., Nuclear magnetic resonance spectroscopy. Carbon-13 chemical 40. Reppe, W,, I shifts of chlorinated organic compounds. / Org Chem.. 39,1276. 1974. Cycloociate* 7. Lauterbui, P. C, Some applications of C'1 nuclear magnetic resonance spectra to organic chemistry, Ann. S-7 41. Huisgrn, R,, Acad. Set.. 70,841, 1958. Am. Chem. 8. Mtyajimv G. and Takahashi, K-, Carbon-13 nuclear magnetic resonance spectroscopy. 111. Chloro-subsututed ' 42, Roedig, A. an ethanes and ethylenes,/ Phys. Chem., 75. 331.1971, 43. Roedig, A., 1 9. Goldstein, J. H., Quadrupole coupling and bond character in the vinyl halides, / Chem. Phys.. 24, 106, 1956- 1 ocutetiaene 10. Meal, H. C,, Zeeman quadrupole spectra of p-chloroanilme and p-chlorobenzylchlonde, / Chem. Phys., 24, 1011- 44 Roedig, A., 1956. , PolyhaJogend 11. Roedig, A., Uber Perchloricrung und Chlorolyse in der Butan-und Pentan-Reihe, Leibigs Ann. Chem., 574, 1 - - i 45, Eisenhuth, L. 195*. 12. Uehleke, H,, Hellmer, K. H.. and Tabarelli, S.. Binding of ' 4C-carbon tetrachloride to microsomal proteins in H, energy s 6. Roedig. A.. and formation of CHG, by reduced liver microsomia. Xenobiotica, 3, 1, 1973. Chem. Ber . 1 13. Fry. B. J- Taylor, T,, and Harhway, D. E-, Pulmonary elimination of chloroform and its metabolite in man. Aren. Ini. Pharmacodyn. Ther., 196. 98. 1972. 406 `-PC Critical Reviews in Toxicology SL 066539 is also extreme)) omposes immediate)), phosgene and carbos zing effect of chlorine d bonds has also been i less intensity) with. 17 i, this thermally un. lowly above 25C) i f chlorinated acetylit yet been invest!^ 21. 'hich is fonned from foethanefs), or acetylivironments produces symptomatology of Koble, V. L. end Anders, M. W., Metabolism of dihalomethines to carbon monoxide. II. In vino studies. Drug Meteb. Dupoi., 3,104,1975. Btttlct, T. C, Reduction of carbon tetrachloride in vivo and reduction of carbon tetrachloride and chloroform in vitro by tissues and tissue constituents, J Pharmacol. Exp. Ther.. 134, 311, 1961. Recknagel, R. 0. and Ciende, E, A., Jr., Carbon tetrachloride hepatotoxicity: An example of lethal cleavage, C.R C. Crit. Rev. Toxicol, 2,263, 1974. Koch, R. R., Glendt, E. A., Jr,, and Recknagel, R. 0.. Hepatotoxicity of bromotnehloromethane - Bond diasociation energy and lipoperoxidation,Biochem. Pharmacol.. 23,2907. 1974. Ken, J, A., Bond dissociation energies by kinetic methods, Oiem. Rev,. 66,465, 1966. Benson, S. W., Bond energies, J Chem. Educ., 42,502, 1965. McLean, A. E. M,, Effect of halogenated hydrocarbons on microsomal cytochrome (P-450), Biochem. J,, 103. 13P, 1967. Ullrich, V. and Schnabel, K. H,, Formation and binding of carbaniow by cytochrome P-4J0 of liver mietosomes, Drug Metab. Dtspos., I, 176,1973. Heppet, L. A. and Porterfield, V. T-, Enzymatic dehalogenation of certain brominated and chlorinated compounds. J. Biot. Chem., 176, 763,1948. Van Dyke, R. A., Metabolism of volatile anesthetics. 111. Induction of microsomal dcchlorinating and ether-cleaving enzymes, J. Pharmacol. Exp Ther.. 154, 364,1966. /etsible damage to minantly the nervus as well as experiind tubular nephro10 s Whether these the reactive dichloro;s is open to further Van Dyke, R. A. and Chcnoweth, M. B., The metabolism of volatile anesthetics. II. In vitro metabolism of methoxyflurane and haiothane in nt liver slices and cell fractions,Biochem. Pharmacol, 14.603, 2965. Van Dyke, R. A. and Wineman, C G-, Enzymatic dechlorination. Dechlorination of chloroethanet and propanes in vitro,Biochem. Pharmacol, 20,463, 1971. Spenser, H. C., Rowe, V. K,, Adams, E. M., McColliste, D. D,, and Irish, D. D,, Vapor toxicity of ethylene dichlonde determined by experiments on laboratory animals, Arch. Ind. Hyg.. 4,482,1951. Torkdioft, T. R., Oyen, F., McCollistet, D. D., and Rowe. V. K,, Toxicity of 1,1,1-trichloroethane as determined on laboratory animals and human subjects, Am. Ind. Hyg. Assoc. J., 19, 353, 1959. Carpentet, C P,, Smyth, H. F., Jt., and Pozzani, U. V., The assay of acute vapor toxicity and the grading and interpretation of remits on 96 chemical compounds, J. Ind. Hyg.. 31, 343, 1949. Yllner, S,, Metabolism of pentachioroethane in the mouse. Acre Pharmacol. Toxicol, 29,481, 1971. Fowles, J. S. U, Some hepatoioxic-aetions of hexaehloroethane end its metabolites in sheep, Br. J. Pharmacot. 35. 530,1969. Yllnet, S., Metabolism of 1,1,2,2-tetrachloroethane-'4 C in the mouse, Acta Pharmacol Toxicol, 29,499, 1971. Hayes, W. J_, Quinby, G. .. Walket, K, C, Elliot, J. W,, and Uphoit. W. M,, Stonge of DDT and DDE in people with different degrees of exposure to DDT, AMA Arch. Ind. Health, 18. 398,1958. AftMin, M., Present status of biochemical research on the insecticide resistance problem. Bull. Who, 29($uppl.), 69, 1963, Sternbuig. J. and Kearns, C. W,, Pentachlorocydohexene. an intermediate in the metabolism of lindane by house flies,/ Econ. Entomol. 49, 548, 1956. . J. Am. Chem, Soc., 77, 35. Grover, P. L and Sims, P., The metabolism of v-2.3,44.6-ptntachlorocyciohe\-l-enc and -r-hexachlorocyclohe.vane in nts, Biochem. J , 96,521. 1965. ons for the azines, J. Am, 36. Williamaon, D. G. and Cvetanovic, R. J,, Rates of reactions of ozone with chlorinated and conjugated olefines. J Am. Otem. Soc.. 90,4248, 1968. DO SCF calculations on ' 37 Roedig, A,, Voes, G, and Kuchinke, E., Uber o- und S-Perchlor-hexatrien-0,3.5) und deren Reduktion sum f trans- l-tubstnuted-1,3.. p. 3329, 1972. lance spectroscopy. K. ipy. Carbon-13 chemical lie chemistry, Amt. N.Y. . ill. Chloro-substituted r Phys., 24. 106, 1956. Chem. Phyt,. 24, 1011. ; Ann. Chem., 574, 122, ,* I I 39' 40. 41. ' 42. -43. 'U ! 45. Triaeetylen,Liebigs Ann. Chem., 580 . 24,2953. Roedig, A. and Bememann, P,, Zur Kenntms von hochchlorierten Vinylathem. l-Athoxy-pentachlor-butadien-(l,3) aus Perchlor-butadien. Liebigs Ann Chem., 600, 1, 1956. Fostdt, M. and Roedig, A.. Notiz zut Darstellung von Dichlormaleinsaureanhydnd aus Hexachlorbutadien, Chem. Ber., 106,1363,1973. Rappe, W,, Sdilichting, 0,, Klager, K., and Toepel. T., Cyelisierende Polymerisation von Acetvlen. I. Uber Cydooctatetraen, Liebigs Ann. Chem.. 560, 1,1948. Haugen, R,, Boche, G,, and Huber, H,, The halogenation of cyelooctatetraene via 8-halohomotropyiiutn ions, J Am, Chem. Soc., 89, 3345.1967. Roedig, A. and Bonse.G., unpublished results. Roedig, A., Helm, R,, West, R,, snd Smith, M,, Structures of the dunets of perchlorobutenyne, OcUchlorocyciooctatetreene ind ocUchlorobicyelo-)4.2.0|-octatiiene-[2.4.7),Tetrehedron Lett., p. 2137,1969. Roedig, A., Borne, G, and Helm, R,, Cydooctatetraen-dihydropentalen-umlagerung von Perchior-COT und etnige Polyhaiogenderivate des Bicycio (3.3.01 octant, Chem. Ber., 106, 2156, 1973. Eisenhuth, L. and Hopf, H,, Gas phase pyrolysis of trans- and cis-l,2-diethynylcydobutane. A new entry in the C, Tosomal proteins m vitro metabolite in man, Arch. H, energy surface, J Am Chem. Soc.. 96,5667,1974. H. Roedig, A., Bonse, G-, Helm, R,, and Kohlhaupt, R, Konstitution und Reaktivitat der dimeitn Perehlorbutenine, Chem. Ber., 104,3378,1971. October 1976 407 SL 066540 47. Cava,M.P. and Mitchell, J.M,, Cyclobutadiene and Related Compounds, Academic Pres, New York, 1967,157. : 48. Mno, K_ Kusudi, K., end Fujino, A_ Dimen of perchJoro-(3,4-dimethylenecyclobutrne). U. Perehloro-(3,4,7,8- tetramethylenecydoocudiene), Tetrahedron Lett., p. 137J, 1968. 79. Kappui. R, Bolt, H. chloride to macromole 80. Bolt, H. M,, Kappus 153,1976. 49. Doering,W.V.E. and Wiley, D. W'..Heptxfulvene. (Methylenecycloheputriene), Tetrahedron, 11,183, 1960. 81. Watanabe. P. G,, Mcl, 50. Roedig, A., Forach, M,, Hiveiux, B,, and Scheutzow, D,, Valenziiameriserung von Perehlot-*-methylenbv m rats, Toxicol. Appl. cyclo(3.2.Q)-heptadien-(2.6l zum Perchlorheptafulven, Tetrahedron Lett., p. 2613, 1972. 'EY. Bonse, G. and Urban, Th,, Oxidative metabolism of chlonnited ethylene*, Naunyn Schmiedeberp Arch. 82. MilUer, G. and Not 1975. Pharmacol., 287.R101, 1975. li Bonse, G_ Urban. Th,, Reichert, D., and Hcnachler, D., Chemical reactivity, metabolic oxirane formation and 83. YUnet, S,, Metabolis.. 84 Rannug, U,, Johansso biological reactivity of chlonnated ethylenes in the isolated perfuaed rat liver preparation, Biochem. Pharmacol., 24, 1829,197J. ,'T. Daniel, I. W., The metabolism of JtCl-labelied trichloroethylene and tetrachioraethylene in the rat, Biochem. activation, A mbio, ? 85. Bartsch, H,, Maiavei in S. typhtmunum s Pharmacol.. 12, 795,1963. 54. Lcibman, K. C, Metabolism of *TRI" in liver microtomes. 1. Characteristic! of the reaction, Mol Pharmacol. 1, 86. Claim, H,, Bonse, < carcinogenicity of ch 239, 1963. 2013, 1975. 55. Byington. K. H, and Leibman, K. C,, Metabolism of trichloroethylene (Tri) in liver microsomes. II. Identification of 87. Bartsch. Maiavei the reaction products as chloral hydrate, Mol. Pharmacol, 1,247,1965. ' 2-chlorobutadiene in 56. Leibman, K. C and Aliifter, W. J,, Metabolism of trichloroethylene in liver microsomes. III. Induction of the enzymatic activity and its effect on exaction of metabolites, J. Pharmacol, 157,574, 1967. 88. Henschler, D-, Bonse rules, Proc. 3rd w~ 57. Frankel, D. M., Johnson, C. E-, and Pitt, H. M., Preparation and properties of tctrichloroethylene oxide, /. Org. Chem., 22, 1119, 1957. 5S. Ikeda, M. and Imamura, T., Biological half-life of trichloroethylene and tetiachloroethylene in human subjects, InL Arch. Arbensmed., 31, 209, 1973. 1 i 90. Oeach, F,, Kxuc substrates and lReport of > Worxu.. Report 75/001, Ly 59. Cole, W. J., Mitchell, H. G,, and Salamonsen, R. F., Isolation, characterization and quantitation of Chloral hydrate as 91. Maltoni, C and L a transient metabolite of trichloroethylene in min using electron capture gas chromatography and mas Environ. Res., 7, 31 . ftagmentography,/. Pharm. Pharmacol,. 27, 167,1975. 60. Butler, T. C, Metabolic transformation of Tri, / Pharmacol. Exp. Ther., 97,84,1949. 61. Uehleke, H,, Poplawiki, S.. Bonse, G,, and Henschler, D., Spectral evidence for 2.2,3-trichlorooxirane formation 92. Department of Health 93. Viola, P. L. et aL, a94. Roedig, A., Markl, during microsomal trichloroethylene oxidation, Naunyn Schmitdeberfs Arch. Pharmacol, 293(Suppl R), 253, 1976. 62. Derkotch, J,, perional communication, 1974; Poluektov, V. A. and Mekhryushev, Yu. Ya* Radiation-chemical 1963, 95, Roedig, A., Bischol 3-H-Pentachlorprope. oxidation of trichloroethylene, Zh. Fiz. Khim., 45, 2335, 1971. 63. Ostenvieher, F,, PhX>. thesis, University of Wien, 1967; Mekhryushev, Yu. Ya. and Pohrektov, V. A^ Kinetics of the thermal isomerisation of mchloruepov'ethane,Rut*. J. Phys. Chem., 47,959, 1973. 96. Roedig. An Detzer. 97. Roedig, A and D< 749, 153. 1971. 64. Leibman, K. C. and Ortiz, E,, Microsomal metabolism of chlorinated ethylenes, 6th InL Congr. PharmacoL, j 98. Roedig, A- Detzer. t Helsinki, Abstr. 257, Nr. 608,1975. 60. 1971. 65. McDonald, R. N. and Schwab, P. A., Molecular rearrangements. II. Chlorine miration in the epoxide-carbonyl \ 99 Roedig, A and H rearrangement,/ Am. Chem.Soc.. 85,4004, 1963. Dimeren. Chem. Be., 66. Griesbaum, G., Kibar, R., snd Pfeffer, B.. Syntftese und Stabilitat von 2,3-Dichloroxiranen. debits Ann. Chem., p. 100. Ott. E-, Uber das t 214, February 1975. handhabenden Mo! ' 67. McDonald, R. N. and Steppd, R. N., Molecular rearrangemenu. XI. The synthesis and neat, thermal rearrangement 101. Roedig, A. and Ko! of (+MlRJR)-2-chloronorbomene exo-oxide,/. Am. Chem. See.. 92, 5664, 1970. ' 102. Henschler. D,, Bro 66. Nagendrappa, G. and Griesbaum, K., Rearrangement of 2,3-dich)oro-2-norbomene epoxide, Chem. Ind., p. 902, . Umgang mtt Vinyhde 1973. 103. Reichert, D., Ewald. 69. Kobrich, G,, Grosser, J., and Wemer, W,, Zur Umlagerung von Li-Alkoxiden aus DichlormethyUithium und * Toxicol, 13, 511. Carbonylvcrbindungen in a-Chloroxirane und e-Chloraldehyde, Chem, Ber.. 106, 2610, 1973. , 104. Reichert, D.. Brin 70. Gaertnet, G. W. and Ramey. D. E,, Verfahren zur Oxydation von Tnehlorsihylen zu Dichloracetylchlorid, Pat Shell Int. Research Maatsehappij N.V.Den Haag (Niederlande), Schweiz. Patent 464879,1968. | Naunyn Schmiedebe 1 105. Siegel, J,, Jones, R. 71. Poluektov, V. A. and Dobrov. I. VM Reaction of trichloroethylene oxide with alcohols, Zh. Prikt. Khim.. 44, 2759, continuous inhalat 1971. 72. Reichert, D. and Bashti, N,, Metabolism and disposition of 1,1-dichloroethylene in the isolated blood-perfused liver of the rat, Naunyn Sclimiedeberrs Arch. Pharmacol., 293(Suppl. R), 255,1976. 73. Bonse, G. and Henschler, D,, unpublished results. 74. Hefner, R. Jr., Watanabe, P. G., and Gehnng, p. preliminary studies of the fate of inhaled vinyl chloride monomer (VCM) in rats, Ann. N. Y. Acad. Sci. 246, 135, 1975. 75. Radwan, Z. and Henschler, D,, Uptake and metabolism of vinyl chloride in the isolated perfused rat liver preparation, Naunm Schrmedeberp Arch. Pharmacol. 287, R100, 1975. 76. Green, T. and Hathwgy, D. E,, The biological fate in rats of vinyl chloride in relation to its oncogenicity, Oiem. Biot. Interact.. 11.545. 1975. 77. Cross. H. and Freiberg, Zur Existent von Chlorathylenoxid,/. Prakt. Chem., 311,506, 1969. 78. Zief, M. and Schramm, C. H,, Chloroethylene oxide, Chem. Ind . p. 660, 1964. 408 CPC Critical Revirycs in Toxico/ofv SL 066541 is, New York, 1967,157. I tene), II. Perchloro*(3,4,7,S. edron. 11, 183, 1960. i von Perehlor-4-methylenbi> 2. mnyn Schmiedebergs Arch. \ 3dlic oxtrane formation and in, Biochem. Pharmacol., 24, 79. 80. 81. 82 83. 84 hylene in the rat, Biochem. Ivf eaction, Mol. Pharmacol.. 1, 4 roiomet. II. Identification of 85. W V. roes. III. Induction of the .967. hloroethylene oxide, J. Org. 8V 89. yisne m human subject*, Int. 90. titation of chloral hydrate at chromatography and man 91. d*r 3-triehlorooxirane formation nacol., 293(SuppL R), 253, 92. 93. 94. Yu. Ya-, Radiation-chemical 95. elrtov, V, A,, Kinetics of the 96. 97 >th Int. Congr. Pharmacol, j 96. .on in the epoxide-carbonyl I 99. men, Liebigs Ann. Chem.. p. 100. neat, thermal rearrangement roxidt, Chem. Ind., p. 902, 101. '102. Dschlormethyllithium und 973. -hloraccrylchlond, Pal Shell 103. r 104. Zh. Prikl Khim., 44, 2759, 105, Kappsis, ft, Bolt, H. Buchter, and Bolt, W,, Rat liver microsomes catalyse covalent binding of 1* C-vinyl chloride to macromolecules. Nature, 257, 134. 1975. Bolt, H. M,, Kapput, H-, Buchter, A., and Bolt. W,, Disposition of 1,2-'4 C vinyl chloride in rat. Arch Toxicol., 35, 153,1976. Watanabe, P. G,, McGowan, G. R- and Gehring, P. J,, Fate of [`4 C] vinyl chloride after single oral administration in rats. Toxicol. Appl Pharmacol., 36, 339,1976. MUlleT, G. and Norpoth, K,, Bestimmung zweier Urinmetabolite des Vinylchlorids, Narurwissenschaften, 62, 541, 1975. YUner, S,, Metabolism of chloroacetate-l-'*C tn the mouse, Acta Pharm Toxicol.. 30, 69, 1971. Rannug, U., Johansson, A- Rimd, C., and Wachtmeister, C. A-, The mutagenicity of vmyl chloride after metabolic activation,Ambio. 3, 194, 1974. Bansch, PL, Malaveilie, C,, and Monteano, IL, Human, rat and mouse liver-mediated mutagenicity of vinyl chionde in 5. ryphimurium strains, Int. J. Cancer, IS, 929,1975. Gram, H-, Bonse, G-, Radwrn, Z~, Reichert, Dm and Henachler, D., Mutagenicity in vitro and potential carcinogenicity of chlorinated ethylenes as a function of metabolic oxirane formation, Biochem. Pharmacol., 24, 2013, 1975. Bartsch, H.' MalaveOle. C, Montetano, R., and Tomatis, L., Tissue-mediated mutagenicity of vinylidene chloride and 2-chlorobutadiene m Salmonella typhimurtum, Nature, 255,641, 1975. Henschler, D,, Bonse, Gn and Gram, H-, Carcinogenic potential of chlorinated ethylenes - tentative molecular ruies, Proc. 3rd WHO-I.A.R.C, Meet., Lyon, November 3, 1975. Oesch, F,, Kaubisch, N,, Jenna, D. M,, and Daly, J. W,, Hepatic epoxide hydiase. Structure-activiry relationships for substrates and inhibitors, Biochemixtry, 10,4858,1971. Report of a Working Group on Epidemiological Studies on Vinyl Chloride Exposed People, 1_A.R.C. Intern, Tech, Report 75/001, Lyon, 1975. Miitoni, C. and Lefemine, G,, Carcinogenicity bioassays of vinyl chloride. 1. Research plan and early results, Environ. Bes., 7, 387, 1974. Department of Health, Education and Welfare, Washington, D.C., Memorandum, March 20,1975. Viola, P. 1_ et aL, cited in Reference 87. Roedig, A., Markl, G., and Heinrich, B., Perchlorptopadien-{1.2), ein hochreaktives Allen, Angrw. Chem.. 75, 88, 1963. Roedig, A., Bischoff, F., Heinrich, B-, and Markl, G-, Perchlorallen als Zwischenstufe der Dehydrochlorierung von 3-H-Pentachlorpropen-fl) ru Perchlor-1.2-dimethylen-cyelobutan, Liebigs Ann. Chem., 670, 8,1963. Roedig, A., Dctzer, N,, and Friedrich, H. J., Tribromailen und Perbromallen,Chem., 76, 379, 1964. Roedig, A, and Detzcr, N,, Thermuch instabile Aliene. VIII. Trichlor-tithoxycarbonyl-allen, Liebigs Ann. Chem.. 749, 153, 1971. Roedig, Dctzer, N, and Bonse, G,, Thermisch instabile Aliene. IX. Trichlurbromallen, Liebigs Ann. Chem.. 752, 60,1971. Roedig, A, and Heinrich, Bm Thermisch initabilie Aliene. IV. Einige Reaktionen des Perchlorallens und seines Dimeren, Chem. Ber., 100, 3716, 1967. Ott, E,, liber das Diehloracetylen. 111. Mitteil Darstellung und einige Vorlesungsversuche mit der gefahrlos ru handhabenden Molekulverbindung mit Ather, Chem. Ber.. 75, 1517, 1942. Roedig, A.and Kohlhaupt, R,, Dimerisierung von Perchlorbutenin, Tetrahedron Lett., p. 1107, 1964. Henschler, D-, Broscr, F,, and Hopf, C. H,, Polyneuritis cranialis durch Vergiftung mit chlorierten Acetylenen beim Umgang mit Vinylidenchlorid-Copolymeren, Arch. Toxicol.. 26, 62, 1970. Reichert, D,, Ewald, D-, and Henschler, D,, Generation and inhalation toxicity of dichloroacetylen. Food Cosmet. Toxicol., 13,511, 1975. Reichert, D-, Brinke, Cm Bannasch, P_ and Uebaidt, Gm Neuro- and nephrotoxic effects of dichloroacetylene. Naunyn Schmiedebergs Arch. Pharmakol. 274(Suppl.), R90, 1972. Siegel, J,, Jones, R. A., Coon, R. Am and Lyon, J. P.. Effects on experimental animals of acute, repeated and continuous inhalation exposures to dichloroacetylene mixtures, Toxicol. Appl. Pharmacol.. 18, 168, 1971. related blood-perfused liver te of inhaled vinyl chloride isolated perfused rat liver to its oncogenicity, Chem. . 1969. October 1976 409 SL 066542