A SYNTHESIS OF 3,3,3-TRICHLORO-1,2-EPOXYPROPANE FROM THE TETRAHALOPROPANE DERIVED FROM A

CARBON TETRAHALIDE AND ETHYLENE1

WILKINS REEVE AND LEONARD LV. FINE Chemistry Department, University of ilfiryland, College Park, ,4faryland, Lr.S..4.

Received April 2, 1963

ABSTRACT

A study has been made of the reactions involving the addition of bromotrichloronlethane to ethylene to give 3-bromo-l,l,l-trichloropropane, subsequent dehydrohalogenation of this t o 3,3,3-trichloro-1-propene, and the isomerization of the latter to 1,1,3-trichloro-1-propene; the experimental conditions have been improved so that the minimurn yield obtained in any one step is 78%. The 1,1,3-trichloro-1-propene is converted to a chlorohydrin in 36% yield by reaction with tert-butyl hypochlorite, and the chlorohydrin is converted in 61% yield to 3,3,3-trichloro-1,2-epoxypropane by treatment with base. The reaction of 3,3,3-tr~chloro-1- propene with n~ethoxide ion to form 1,l-dichloro-3-methoxy-1-propene provides another example of an S N ~ ' reaction.

A corivenient synthesis of 3,3,3-trichloro-1,2-epoxypropane was desired to make the compound available in relatively large amounts for another synthetic program. I t had previously been prepared on a small scale by the reaction of diazomethane with chloral (I).

The synthesis which was developed involved the addition of carbon tetrachloride or bromotrichloromethane to ethylene to form the tetrahalopropane, which was then de- hydrohalogenated and the resulting olefin isomerized and then converted to the epoxide via the chlorohydrin. Soine of the reactions have been reported on previously, but signifi- cant improvements have been worked out for these steps and much new information has been developed.

KOH in CHaOH 0 C2H4 + CC1,X i XCH2CH2CC1, > [XCHz-CH-CC13]

Ia, X = C1 Ib, X = Br

'" J 1 I1

CH2=CH-GC1s XCHzCH=CC12

\ J IVa, X = C1 IVb, X = Br (not

isolated)

Reaction of Carbon Tetrachloride with Ethylene The addition of carbon tetrachloride to ethylene has been reported previously (2), but

in our hands the reaction was quite unsatisfactory when carried out batchwise according to the published directions. A steel reaction vessel fitted with a glass liner was used and the latter was filled one eighth full with carbon tetrachloride. Ethylene was fed in a t 7-10 atm pressure. At 80' and with 0.8% benzoyl peroxide as the free-radical initiator, about 11% of the theoretical yield was the most that could be obtained in one run, although this corresponded to a yield of 25% when allowance was made for the recovered carbon tetrachloride. -4s has been reported previously ( 2 (a ) ) , telomers were produced in addition to the desired product.

' T h i s investigation was supported i n part by a Predortoral Fellowslzip to L. TV. F. frollz the Divisioiz of General ~Vedical Studies, Cnited States Public Health Service.

Canadian Journal of Chemistry. Volume 41 (1963)

2231

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2232 CANADIAN JOURNAL OF CHEMISTRY. VOL. 41, 1963

A series of peroxides was studied, and i t was found that tert-butyl perbenzoate was superior to benzoyl peroxide for this reaction when equal amounts of catalysts were used. The optimum conditions involved using 2.4% of tert-butyl perbenzoate; the yield was then 28Y0 before allowing for recovered carbon tetrachloride. The results are summarized in Table I.

TABLE I The reaction of ethylene with carbon tetrachloride and with

bromotrichloromethane

Catalyst

Benzoyl peroxide t-Butyl perbenzoate

Conditions Reaction temperature, OC 80 115 Pressure of ethylene, atm 7 to 10 7 to 10 Volume of glass liner, ml 1125 1125 Volume of starting CClaX, ml 125 125

n-ith CC14 Moles catalyst/mole CCla Yield of 1: 1 adduct, % Yield of telomers, 70 Recovered CC14, yo

\Vith CBrC13 Moles catalvst/mole CBrCli Yield of 1: f adduct. %

'n

Yield of telomers, % ' - Recovered CBrC13, Yo

*In larger runs, it was found that increasing the amount of catalyst did not increase the yield.

Peroxides which were less effective than the above included lauroyl peroxide, hydroxy- heptyl peroxide, and tert-butyl hydroperoxide. All of the peroxides were used a t reaction temperatures (70 to 130') which corresponded to a half-life of 3 hours for the pure catalyst when decoinposed thermally by heating alone i n benzene a t the given temperature (3).

Reaction of Bromotrichloromethane with Ethylene As shown in Table I , lxomotrichlorome?hane adds to ethylene to give a 78% yield of

the 1 : l adduct with either benzoyl peroxide or tert-butyl perbenzoate as catalysts.* No telomers were formed and very little of the bromotrichloromethane was unreacted. Haszeldine previously observed that this addition reaction using benzoyl peroxide would occur in 60% yield ( 2 ( d ) ) , and the reaction has also been reported to o x u r in unstated or lower yields by others (4). This provides an excellent example of a chain-transfer reaction, [I], taking precedence over the chain-propagation reaction, [2], observed with carbon

.CH2CH*CC13 + BrCC13 + BrCH2CH2CC13 + .CC13 [I] . C H ~ C H Z C C ~ ~ + CH~=CHS -+ .CH2CH,CH2CH2CCI, 121

tetrachloride because of the greater lability of the carbon-bromine bond in bromo- trichloromethane as compared with the carbon-chlorine bond in carbon tetrachloride.

I t was observed that the amount of catalyst required depended on the relative volumes of the gas and liquid phases inside of the glass liner. When the liner was filled 17% (50% more than the volume specified in Table I) , the concentration of the tert-butyl perbenzoate catalyst had to be doubled in order to obtain a 78% yield.

*The addition of bromotrichloromethane to ethylene at 120' and 50 a tm pressure in the absence of peroxides has been used successfully by others as a preparative method. However, Elsev and Saure (H. Elser and S. Saure. Angew Chem. 74, 255 (1962)) have recently reported the occurrence of a zliolent explosion under these conditions.

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REEVE AND FINE: 3,3,3-TRICHLORO-1.2-EPOXYPROPANE 2233

Dehydrohalogenation of the Tetrahalopropanes The base-catalyzed dehydrohalogenation of 1,1,1,3-tetrachloropropane has been

previously studied and both of the olefins I11 and IVa have been reported to be obtained in yields of 31 and 12% ( 5 ) , 50 and 30% ( 6 ) , and 57 and 30% (2(d)) respectively. The dehydrohalogenation of 3-bromo-l,l,l-trichloropropane has been reported to give 57% of olefin I11 (7).

From the theoretical standpoint, this dehydrohalogenation of the 1,1,1,3-tetrachloro- propane is of considerable interest since the intermediate carbanion I1 should be capable of forming either of the two olefins, I11 or IV. The conformation of the tetrahalopropane required for the formation of olefin I11 is given in Fig. 1. This conformation might be

considered to be unlikely due to both steric interaction and dipole-dipole repulsion of the groups in this skew configuration. Therefore, formation of olefin I11 might be considered less likely than formation of olefin IV. The formation of the latter involves no steric problems and the developing double bond would have considerable resonance stabilization from the two vinplic chlorine atoms. Despite these considerations, the results in Table I1 show that the trichloromethyl group is so inert that the major reaction product is olefin 111.

TABLE I S - - -

Percentage yields of products in dehydrohalogetlation reaction*

Products From ClCH2CH2CC13 From BrCHzCH2CC13

CHFCHCC~, ( 1 1 1 ) 55 80 XCHcCH=CCI, ( IV) 24 0 CH,OCH2CH=CCI2 (V) 11 14

*Twofold excess of potassium hydroxide in methanol solvent at 26' for 90 minutes.

Our results are based on vapor phase chromatographic analysis of the reaction products before distillation, whereas the results of earlier workers are based on careful fractional distillation. I t is now apparent that some isomerization of olefin I11 to olefin IV can occur under distillation conditions. Our procedure differed from the others also in that a twofold excess of methanolic potassium hydroxide was e~nployed a t 25' and the reaction was carried out in 90 minutes. Earlier workers used ethanolic potassium hydroxide a t temperatures fro111 0 to 25', base concentrations from 0 to 30% in excess of theory, and reaction times up to 6 hours.

The increased amount of olefin I11 formed from the 3-bromo-l,l,l-trichloropropane is in accord with the known much greater tendency of alkyl bromides relative to alkyl chlorides to undergo an elimination reaction rather than a substitution reaction (8). I t is probable that a small amount of 3-bromo-1,l-dichloro-1-propene (IVb) is also formed and

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REEVE AKD FINE: 3,3,3-TRICHLORO-1,2-EPOXYPROPXNE 2235

3-Bromo-l,l,l-trichloropropane (Ib) The apparatus used was a rocking-type steel autoclave (1640-in1 volume) fitted aiLh a glass liner (1125-tnl

inner volume). In the glass liner were placed 125 ml (1.3 moles) of freshly distilled bromotrichloronlethane and 1.5 g (0.0062 mole) of dibenzoyl peroxide. The autoclave was flushed thoroughly with ethylene, the ethylene pressure raised to 100 lb/sq. in., and the autoclave then rocked and heated to the initiation tempera- ture of l15", a t which point the pressure began to drop. Each time the pressure fell to 100 lb/sq. in., the autoclave was recharged to 175 Ib/sq. in. The rate of pressure change was slow a t first, reached a maximum, and then gradually tapered off with about 3 hours' reaction time required. Distillation yielded 230 g (78% yield) of 3-bromo-l,l,l-trichloropropane, b.p. 78-80" a t 26 mm, nD26 1.5126. The physical constants are in agreement with the literature values (4(a)).

Dehydrolzalogenation of 3-Bro~lzo-l,l,l-trichloropropane Over a 30-minute period, 56 g (1 mole) of potassium hydroxide dissolved in 130 ml of methanol was

added with mechanical stirring to 112 g (0.5 mole) of 3-bromo-l,l,l-trichloropropane. The temperature was maintained a t 25'with an ice-water bath. Stirring was continued for 1 hour, the reaction mixture then poured into 300 ml of cold water, the organic layer washed once with water, dried over anhydrous magnesium sulphate, and then distilled through a modified Widmer column. There was obtained 57 g (807, yield) of I , i , l - t r i ch lovo- I -pwene , b.p. 100-100.5" a t 760 mm, n~~~ 1.4684. The physical constants are in agfeement

with the literature values (5). Infrared spectrum, vmax: 1890 (vinyl overtone), 1630 (>c=c< weak),

1410, 1125, 970, 945, and 813-770 cm-I. There was also obtained 12 g (14% yield) of I,l-dichloro-3-methoxy-1-propene (I7), b.p. 132-133' a t 760

mm. For preparative purposes, the preferred synthesis of this involved treating 1,1,3-trichloro-1-propene (IVa) according to the above procedure, but with refluxing a t approximately 80" for 6 hours after the meth- anolic potassium hydroxide had been added to the reaction mixture. The yield was 80% of the theoretical. Infrared spectrum, v,,,: 2975, 2875, 1625, 1450, 1370, 1360, 1285, 1225, 1185, 1150, 1115-1065, 980-960, 912, 878-863, and 825 cin-I. Anal Calc. for C4HoC120: C, 34.08; H, 4.29. Found: C, 34.25; H, 4.47.

l,i ,S-Trichloro-I-propene (I Va) Freshly distilled 3,3,3-trichloro-1-propene (146 g, 1.0 mole) was placed in the glass liner in the autoclave

an& heated for 5 hours a t 150'. Shaking was not necessary. After cooling overnight, there was obtained on distillation 139 g (95% yield) of 1,1,3-trichloro-1-propene, b.p. 130-131" a t 760 mm. The physical constants were in agreement with the literature values (6(a)). Infrared spectrum, v,,,: 3025, 2930, 1725, 1690, 1605, 1475, 1285, 1245, 1175, 1070, 945, 880-815, 740, and 695-675 cnl-I.

1,1,1,3- Tetiachloro-2-propanol ( VII) In a 500-in1 3-necked flask, equipped with a Hershberg stirrer and a thermometer, were placed 15 g

(0.1 mole) of 1,1,3-trichloro-1-propene, 24 g of glacial acetic acid, and 250 ml of water. To this, 22 g (0.2 mole) of teut-butyl hypochlorite (12) was added dropuise over a 20-minute period with the temperature of the reaction mixture being maintained a t 0'. After another 30 minutes, the reaction mixture was allowed to warm up to room temperature and was stirred for an additional 2 hours. The aqueous layer was separated and extracted with chloroform, the chloroform combined with the organic layer, washed once with water, dried, and distilled through a illodified L45dmer column. There was obtained 7 g (36% yield) of 1,1,1,3- tetrachloro-2-propanol (VII), b.p. 98-100" a t 17 mm, noz5 1.5165. Reported values are: b.p. 87-90' a t 14 mm and no20 1.5145 (10). Analysis by v.p.c. indicated the material to be 907, pure. Anal Calc. for C3H4C1,0: C, 18.21; H, 2.03. Found: C, 18.48; H, 2.20.

There was also obtained 127, of unreacted starting material, and 9 g (427, yield) of 1,1,1,2,3-pentaclzloro- propane (VI), b.p. 81-83" a t 17 mm, identified by analysis and by comparison with an authentic sample.

S,S,S- Trichloro-1 ,%-epoxypropane ( VIII) In a 250-ml 3-necked flask equipped with a dropping funnel, Hershberg stirrer, and a thermometer was

placed 20 g (0.1 mole) of 1,1,1,3-tetrachloro-2-propanol. One milliliter of phenolphthalein indicator solution was added and a 1 N methanolic (or ethanolic) potassium hydroxide solution was introduced dropwise a t such a rate that the reaction mixture never became highly colored. The temperature was maintained a t 25 to 35'. Two to three hours were required for 80% of the stoichiometric amouilt of base to be added, a t which point the reaction was stopped by adding 200 tnl of mater and separating the layers. The organic layer uras washed twice with water, dried over anhydrous magnesium sulphate, and distilled. There was obtained 10 g (617, yield, based on the chlorohydrin), b.p. 47-49" a t 17 mm, noz6 1.4783. Literature values are b.p. 39-40" a t 11 mm and 1.4768 (13). An authentic research sample from an industrial source had a boiling point of 147-149" a t 760 mm, noz6 1.4768.

Infrared spectrum of the 10-g sample, v,,,: 3065, 3010, 2920, 1475, 1385, 1270, 1155, 1140, 1105, 1075, 955, 885, 848, and 830-770 cm-I. Anal Calc. for C3HBC1,O: C, 22.32; H, 1.87; C1, 65.90. Found: C, 22.10; H, 1.81; C1, 66.15.

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2236 CASADIAN JOURNAL OF CHEMISTRY. VOL. 41, 1963

ACKSOWLEDGMEKTS

We wish to express our appreciation to Drs. Ellis Lippincott and Francis Powell for their assistance in obtaining and interpreting the infrared spectra. The financial support provided by the National Institutes of Health is deeply appreciated.

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