[CONTRIBUTION FROM THE NOYESCHEMICAL LABORATORY, UNIVERSITY OF ILLINOIS]
LEVINSTEIN MUSTARD GAS. V. THE ACTION OF CHLORINE AND SULFUR CHLORIDES Opr' THE bis(2-CHLOROETI-IYL) POLI'SULFIDES' REYNOLD C. FUSON, DONALD M. BURNESS, ROBERT E. FOSTER, ROBERT D. LIPSCOMB
AND
Received March 16, 1946
The discovery that bis(2-chloroethyl) disulfide is cleaved by chlorine (1) to yield 2-chloroethylsulfenyl chloride (I) raised the question as to the behavior of the higher polysulfides toward this reagent. ClCH2CHzSSCH&H+3
+ CIS
4
2 ClCH2CHzSCl I
Experiment has shown that bis(2-chloroethyl) trisulfide behaves in a similar manner. When it was treated with two moles of chlorine, 2-chloroethylsulfeny1 chloride and sulfur dichloride were obtained. CICHzCHzSSSCH2CHzCl
+ 2 Clz -+
2 ClCHzCHZSCl
+ SClz
As to the mode of formation of the sulfenyl chloride from Iyis(2-chloroethyl) trisulfide, two possibilities were considered: (a) the trisulfide is stripped to bis(2-chloroethyl) disulfide which then undergoes cleavage, or (b) the trisulfide, itself, is first cleaved by chlorine to produce a mixture of 2-chloroethylsulfeny1 chloride (I) and 2-ehloroethyl dithiochloride (11). A sample of the dichloro trisulfide was treated with one molecular equivalent of chlorine, and propylene was passed into the mixture. Two products were obtained and identified as 2-chloroethyl 2-chloro-n-propyl sulfide (111)and disulfide (IV), proving beyond doubt that the reaction involves direct cleavage of the trisulfide (course b). ClCHzCHzSSSCHzCHzCI
+ Clt -+ ClCHzCHZSCI + ClCHZCHzSSCl
I I1 ClCH&HzSCH&HClCK3 111 -+ ClCH2CHzSSCH~CHClCH~ IV This! result also tends to confirm the linear structure for bis(2-chloroethyl) were the cortrisulfide (2). If the angular structure, C1CH2CH2SSCH~CH2CI,
+ CH3CHICHZ ClCH2CH2SSCl + CHSCH=CHz ClCH2CHzSCl
-+
1
8
rect one, the first point of attack by chlorine would be expected to occur at the angular sulfur atom causing the reaction t o follow the first course (l),and no dithiochloride would be formed. This paper is based on work done for the Office of Scientific Research and Development under Contracts Nos. OEMsr-300 and OEMsr-48 with the Board of Trustees of the University of Illinois. 499
500
FUSON, BURNESS, FOSTER, AND LIPSCOMB
When the trisulfide was treated with chlorine until reaction had ceased, the product consisted of sulfur dichloride and a mixture of di- and tri-chloroethylsulfenyl chlorides. A similar mixture was obtained by Phillips, Davies, and Mumford (3) by the exhaustive chlorination of mustard gas. In view of the ease with which chlorine cleaves bis(2-chloroethyl) disulfide and trisulfide it seemed likely that the sulfur chlorides might have a similar action, since they are known to be effective chlorinating agents. Although only a very small amount of the disulfide is present in the final product of the Levinstein reaction (2,4), it is quite possible that it plays an important role a,s an intermediate in the process. Higher polysulfides, such as bis(2-chloroethyl) trisulfide and pentasulfide, are known (2) to form a large fraction of the crude reaction product; therefore, these compounds, as well as the disulfide, undoubtedly are in contact with the sulfur chlorides during the course of the Levinstein reaction. In an attempt to determine the results of such contact, the polysulfides mere subjected to the action of the sulfur chlorides. It was found that sulfur monochloride, like chlorine, acts upon bis(2-chloroethyl) disulfide to produce 2-chloroethylsulfenyl chloride, probably according to the following equation: (CICHzCH2)2Sz
+ 3 SzClz -+
2 ClCHzCHzSCI
+ 2 Sac12
This conclusion is based on the following experiment. A mixture of bis(2-chloroethyl) disulfide with sulfur monochloride waa allowed to stand two days, then treated with cyclohexene. Distillation of the reaction mixture yielded 2-chlorocyclohexyl 2-chloroethyl sulfide and a viscous liquid having the composition of bis(2-chlorocyclohexyl) trisulfide. Further experiments showed that cleavage of the disulfide by sulfur monochloride was rapid, but not instantaneous. These observations suggest a satisfactory explanation for the virtual absence of bis(2-chloroethyl) disulfide in Levinstein mustard gas. It is reasonable to expect that ethylene would react directly with sulfur monochloride to form the disulfide, probably by way of the dithiochloride (11) intermediate. CHZ==CH,
+ S&lZ -+
ClCH2CHzSSCl C"FcH2 I1
P
(CICH2CH&Sa
The disulfide then must undergo cleavage by sulfur monochloride, almost as fast as it appears, with the formation of 2-chloroethy1sulfenyl chloride and sulfur tritadichloride as indicated above. These cleavage products then react normally with ethylene to produce bis(2-chloroethyl) sulfide and trisulfide, respectively.
+
ClCHzCHzSCl CH25CHz --+ (CICH&H&S Sac12 2 CHz=CHz + (ClCHzCH2)2&
+
In contrast to its behavior with the disulfide, sulfur monochloride failed completely to cleave bis(2-chloroethyl) trisulfide. Its only effect was to sulfurize the trisulfide to higher polysulfides; for example, treatment of the trisulfide with two equivalents of sulfur monochloride produced bis(2-chloroethyl) pentasulfide.
LEVINSTEIN MUSTARD GAS.
+
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V
+
(ClCH2CH2)2Sa 2 S&12 -+ (ClCH2CH2)& 2 SCli Clearly this result offers a plausible explanation for the existence of polysulfides higher than bis(2-chloroethyl) trisulfide in Levinstein mustard gas. The sulfur dichloride formed as by-product of the sulfurization undoubtedly reacts at once with ethylene to produce mustard gas itself. Elementary sulfur and methyl tetrasulfide also have been observed to sulfurize the trisulfide (2). With sulfur dichloride, bis(2-chloroethyl) trisulfide was found t o undergo extemive cleavage, with the formation of 2-chloroethylsulfeny1 chloride. Reactions involving bis(2-chloroethyl) pentasulfide and chlorine, or sulfur dichloride, were more complex. Briefly, it may be stated that when the pentasulfide was treated with different amounts of chlorine, 2-chloroethylsulfenyl chloride and polychloroethylsulfenyl chlorides were obtained. Cleavage of the dichloro pentasu.lfide by sulfur dichloride also occurred with the formation of 2-chloroethylsulfenyl chloride, which was identified by means of its cyclohexene adduct, 2-chlorocyclohexyl 2-chloroethyl sulfide. There was evidence for the existence of the corresponding disulfide, which would indicate the formation of the dithiochloride (11) in the reaction. EXPERIMENTAL
Actioit of chlorine on bis(2-chloroethyl) trisuljide. a. Exhaustive chlon'nolysis. To a solution of 30 g. of bis(2-chloroethyl) trisulfide (2) in dry carbon tetrachloride was added 63 g. of chlorine at such a rate that the temperature did not exceed IO". The solvent wlte evaporated and the product distilled under reduced pressure; b.p. 72.575" (13 mm.). After refractionation, the main portion of the product distilled at 77.5" (22 mm.); n: 1.5488. An analysis indicated a mixture of dichloro- and trichloro-ethylsulfenyl chlorides which could not be separated. AnaE. Calc'd for CIHZCI~S:C, 12.00; H, 1.00; C1, 70.9. Calc'd for CZHJCI~S: C, 14.45; H, 1.81; C1, 64.3. Found: C, 13.10; H, 1.27; C1, 65.9. b. Limited chlorinolysis. The above experiment was repeated limiting the amount of chlorine to that necessary t o produce 2-chloroethylsulfeny1 chloride. This was accomplished by treatment of the solution of trisulfide with chlorine for twenty minutes. After standing at 0-5" for three hours, the mixture upon distillation yielded 2-chloroethylsulfenyl chloride; b.p. 44' (12 mm.); n t 1.5370. It was characterized by means of its piperazine derivative, m.p. 117-118' (1). c. Mechanism of ch1om'noZysi.s. A solution of 31.0 g. (0.14 mole) of bis(2-chloroethyl) trisulfide in 110 ml. of dry carbon tetrachloride was treated with 9.0 g. (0.13 mole) of chlorine at such a rate that the temperature did not exceed 3". A 50% excess of propylene was passed in and the solution allowed to stand overnight. Removal of the solvent followed by fractionation i n vacuo yielded 25-30 g. of 2-chloroethyl 2-chloro-n-propyl sulfide, b.p. 69.5' (2 mm.), n t 1.5157 (5),and 10 g. of a compound distilling a t 74-74.5' (1 mm.), n: 1.5518. This proved t o be the mixed disulfide in 35% of the theoretical yield. Anal. Calc'd for CjH10CIzS2: C, 29.3; H, 4.92; C1,34.7; S, 31.3. Found: C, 29.2; H, 4.67; C1, 34.62; S, 31.38. Action of sulfur monochloride on bis(2-chloroethyl) disulfide. A mixture of 0.1 mole of bis(2-chloroethyl) disulfide (2) and 0.2 mole of sulfur monochloride was allowed t o stand at room temperature for two days; then a solution of 0.4 mole of cyclohexene in carbon tetrachloride was added with stirring. Several hours later the mixture was distilled; 13 g. of unchanged disulfide and 7.5 g. of 2-chlorocyclohexyl 2-chloroethyl sulfide, b.p. 104-108° (1 mm.), n: 1.5490, were obtained. The sulfide was characterized by means of its p-toluene-
502
FUSON, BURNESS, FOSTER, AND LIPSCOMB
sulfilimine, m.p. 147-148" (1). An alcohol extract of the residue yielded a brown, viscous liquid, which had the approximate composition of bis (2-chlorocyclohexyl) trisulfide; i t slowly evolved hydrogen chloride. Anal. Calc'd for C12Hz&l&: C, 43.49; H, 6.08; C1, 21.40; S, 29.03. Found: C, 44.08; H, 6.46; C1, 18.97; S, 32.03. I n an attempt to determine the rapidity of the cleavage of bis(2-chloroethyl) disulfide, the above reaction was repeated. The slow, simultaneous addition of sulfur monochloride and cyclohexene to a well-stirred solution of the disulfide in carbon tetrachloride, followed promptly by distillation, yielded none of the expected 2-chlorocyclohexyl 2-chloroethyl sulfide. I n a third experiment a mixture of the disulfide (0.1 mole) and sulfur monochloride (0.3 mole) waa stirred at 35" for twenty minutes. Then 0.6 mole of cyclohexene in carbon tetrachloride was added dropwise over a two-hour period. From this mixture was isolated by distillation 19.8 g. of 2-chlorocyclohexyl 2-chloroethyl sulfide, 47% of the theoretical amount. Action of sulfur monochloride on bis(9-chloroethyl) trisulfide. A mixture of bis(2-chloroethyl) trisulfide with two molecular equivalents of sulfur monochloride was allowed t o stand at room temperature for one week. The low-boiling sulfur chloride waa removed by distillation in vacuo. The residual oil was dissolved in ether, washed with a dilute solution of potassium carbonate followed by water, and dried. Evaporation of the solvent yielded an oil whose physical properties and composition agreed with those of bis(2-chloroethyl) pentasulfide (2). Another experiment was carried out in an attempt t o detect the presence of any cleavage product (sulfenyl chloride) in the reaction mixture. A two-day old mixture of the trisulfide with four molecular equivalents of sulfur monochloride was treated with a n excess of cyclohexene in carbon tetrachloride. Distillation of the product i n vacuo yielded no 2-chlorocyclohexyl 2-chloroethyl sulfide. Action of sulfur dichloride on bis(9-chloroethyl) trisulfide. A mixture of bis(2-chloroethyl) trisulfide (0.1 mole) with sulfur dichloride (0.3 mole) was allowed t o stand for twenty-four hours. The red solution was diluted with carbon tetrachloride, and 0.6 mole of cyclohexene was added slowly. After removal of the volatile materials, distillation of the residue i n vacuo yielded 29 g. of 2-chlorocyclohexyl 2-chloroethyl sulfide, b.p. 102-105" (0.2-0.4 mm.) (1). This corresponds to 67% of the theoretical amount. Action of chlorine on bis(9-chloroethyl) pentasulfide. This reaction was carried out according t o the procedure used in the chlorination of the trisulfide. In the first experiment the theoretical amount of chlorine required t o convert the pentasulfide (2) to 2-chloroethylsulfenyl chloride and sulfur monochloride was used. Distillation of the product yielded the sulfenyl chloride in fair yield and a residue of unchanged bis(2-chloroethyl) pentasulfide (n: 1.670), which amounted t o 20% of the original starting material. The next experiment involved siifficient chlorine t o convert the three odd sulfur atoms t o sulfur dichloride. Cleavage of the polysulfide was complete; the distillate consisted of two fractions. The first, b.p. 4547.5' (14 mm.), proved t o be 2-chloroethylsulfenyl chloride while the second fraction was a mixture of di- and tri-chloroethylsulfenyl chlorides, b.p. 55.5-57.5" (8mm.), n: 1.5490. A n d . Calc'd for CtHsClsS: C, 14.45; H, 1.81. Found: C, 13.78; H, 1.61. A similar mixture was obtained by the exhaustive chlorinolysis of bis(2-chloroethyl) trisulfide. Action of sulfur dichloride on bis(9-chloroethyl) peniasuljide. The procedure described for the reaction between sulfur dichloride and the trisulfide was repeated using 0.1 mole of bis(2-chloroethyl) pentasulfide, 0.5 mole of sulfur dichloride, and 0.9 mole of cyclohexene. Distillation of the product yielded 12.6 g. of 2-chlorocyclohexyl 2-chloroethyl sulfide, b.p. 91-109" (0.3 mm.), n: 1.5473 (l), and 10.7 g. of a higher-boiling fraction which distilled at 116-122' (0.4 mm.), nt 1.5803.
LEVINSTEIN MUSTARD QAS.
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503
Anal. Calc’d for CsHI&12S: C, 45.07; H, 6.62; C1,33.27. Calc’d for CsH&lpSt: C, 39.16; H, 5.76; C1, 28.9. Found: C, 41.30; H, 6.02; C1, 29.11. The analysis and refractive index of this second fraction indicate a mixture of the unsymmetrical sulfide and disulfide. Thus, i t appears that approximately 53y0 of the bis(2chloroethyl) pentasulfide underwent cleavage. SUMMARY
It has been shown that bis(2-chloroethyl) trisulfide is cleaved by chlorine to yield 2-chloroethylsulfenyl chloride and 2-chloroethyl dithiochloride. The use of two .molecular equivalents of chlorine converts the trisulfide to the sulfenyl chloride and sulfur dichloride. Sulfur dichloride likewise brings about a cleavage of the t,risulfide to the sulfenyl chloride. his(2-Chloroethyl) disulfide has been found to undergo cleavage with sulfur monochloride, yielding 2-chloroethylsulfenyl chloride. In contrast to this observation, it has been found that the trisulfide is not cleaved by sulfur monochloride; it undergoes sulfurization to higher polysulfides. These observations afford a satisfactory explanation of the fact that the disulfide is virtually absent from Levinstein mustard gas. URBANA, ILL. REFERENCES (I) FUSON,PRICE,BAUMAN, BULLITT,HATCHARD, AND MAYNERT, J . Org. Chem., Paper I of this series. FOSTER, HATCHARD, AND LIPSCOMB, J. Org. Chem., Paper (2) FUSON,PRICE,BURNESS, IV of this series. (3) PHILLIPS, DAVIES,AND MUMFORD, J. Chem. SOC.,535 (1929). (4) MACINNES AND BELCHER, O.S.R.D. Report. (5) FUSON,PRICE,AND BURNESS, J . Org. Chem., Paper I1 of this series.
