I
W. A. SKINNER, ERNEST BISHOP, DALE TIESZEN, and J. D. JOHNSTON Department o f Chemistry, Stanford Research Institute, Menlo Park, Calif., and Ethyl Corp., Baton Rouge, La.
A N e w Route t o . . . .
Flume-Resistant Polymers Synthesis a n d Polymerization of
3,3,3- Trichloro-Lpropene Dehy d ro brom ination of bro motric hloro met ha ne lea ds to
WHILE
studying the free radical additions of halbgeiated methanes and other halogenated organic compounds to ethylene and substituted ethylenes ( 5 ) , it was discovered that bromotrichloromethane added noncatalytically
Reactions are carried out at relatively low temperatures in the absence of a catalyst. This is an important contri bution as flame-resistant resin and polymers are coming into great demand and simplified processes will make their man uf a ctu re that much more attractive
fl a me-resista nt polymer s
Dehydrohalogenation o f 1 , l ,1 -Trichloro-3-bromopropane
Table I.
Use of sodium methoxide in methanol or diethyl ether gives better dehydrobrominotion
CLCCHgReagent, Moles KOH, 0 . 1 8 KOH, 0 . 3 3 KOH, 0 . 5 7 NaOCHa, 0 . 2 5 NaOCHa, 0 . 2 5 NaOCH3, 0.25
Temp., O
c.
25 100 0 65 25 25
Time, Hr.
CHZBr, Moles
0.25
0.19 0.18 0.51 0.20 0.20 0.22
1 .oo
0.50 2.00 18.00 18.00
CLCClIC=CH CH=CH2,n --CHZCI,~ Yield, yo Yield, %;, 24 20 31 57 57 50
1
1 1 1 1
1
Solvent, h:l.
Ethanol,50 Ethanol, 5 2 HzO,25 Ethyl Cellosolve, 150 Methanol, 50 Methanol, 50 Ether, 50
Boiling point 46 to 48' (108 mm.), reported 44 t o 45' (103 mm.). n$'1.4678, reported (1) n $' 1.4680. * Boiling point 74 to 75' (103 mm.), reported 74 t o 75' (103 m m . ) . n:: 1 4950, reported ( 1 ) n$' 1.4960. a
to ethylene and substituted ethylenes. The reaction of ethylene with bromotrichloromethane led to 1,1,1 -trichloro3-bromopropane in good yields. Thus, the availability of this material made a study of its dehydrobromination to 3,3,3trichloro-1-propene of interest because trichloropropene contains a high percentage (73%) of chlorine which is useful in rendering copolymers of tri-
chloropropene Lvith flame resistant.
other
monomers
Experimental
Use of sodium methoxide in methanol or diethyl ether is the best method of dehydrobromination (Table I) and yields of 57% of 3,3,3-trichloro-l-propene have been obtained. VOL. 51, NO. 1 1
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NOVEMBER 1959
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Table II.
Polymerization of 3,3,3-Trichloro- 1 -propene Yields a New Polymer
Azobisisobutyronitrile, 40 mg. Diacetyl peroxide (25% solution in dimethyl phthalate), 430 mg. Benzoyl peroxide, 205 mg. Radiation, 102 X 106 rep.
60 100
16.0
60 100 25
1.0 6.0 240.0
2.0
0.014
3.8 5.0 5.5
0,036 0.034 0.038
47mg.
110-140
6.0
1.4g. 0 . 5 g.b 5 . 5 g.c
75-110 80-110 45-65
a Solid polymer was isolated by precipitation in methanol and mas reprecipitated by dissolving in either chloroform or acetone and adding methanol. Anal: Calcd. for C3H3C13: C1, i3.3. Found: C1, 62.1. Anal: Calcd. for CsH3Cls: C1, i 3 . 3 . Found: C1, 70.9. Portions of polymer are insoluble in acetone and soften at 155-65O.
LVhen triethylamine, dimethylaniline, or quinoline was used at steam bath temperatures no dehydrohalogenation occurred, most of the original material being recovered. When 0.2 mole of l,l,l-trichloro-3bromopropane was mixed with 0.3 mole of powdered potassium hydroxide and heated on a steam bath a vigorous reaction with tar formation occurred. However, when diethyl ether was used as a solvent (120 ml.), no reaction occurred over a 3-hour reflux period. The reaction of 1,l,l-trichloro-3bromopropane (45 grams, 0.2 mole) with sodium methoxide (13.5 grams, 0.25 mole) in 50 ml. of methanol was carried out under the various conditions in Table I . A new polymer, poly-3,3,3-trichloro-lpropene (Table 11),has been prepared. I n addition to the solid polymer. liquid polymers of lower molecular weight were also produced except in the case of radiation-induced polymerization \vhich took place at ambient temperature. Copolymerization of 3,3,3-trichloro-lpropene and ethylene was carried out in an Aminco rocking bomb by placing 24.2 grams (0.17 mole) of 3,3,3-trichloro-1-propene in the 110-ml. bomb with 1 gram of benzoyl peroxide, purging with nitrogen to remove air, pressurizing to 500 p.s.i.g., with ethylene, and heating at 100' C. for 3 hours. A small amount of a solid polymer, melting point 145' to 155O C. (homopolymer of 3,3,3-trichloro-1-propene) was isolated from the reaction mixture. I n addition, a waxy polymer of 13.5 grams, soluble in the unreacted 3,3,3trichloro-1 -propene, was obtained after removal of the liquid by distillation. The waxy copolymer softened at 75' to 85 ' C. and showed the following analysis: Calculated for 3,3,3-trichloro-l-propeneethylene: C1, 67.00. Calculated for 3,3,3-trichloro-l-propene-2 ethylene: C1, 57.6. Found: C1, 60.0. This copolymer would not support combustion. Copolymerization of 3,3,3-trichloro1-propene (30 grams, 0.021 mole) with vinyl acetate (0.04 mole) using 319 mg.
1 360
of benzoyl peroxide in a sealed, evacuated vial was carried out for 7 hours at 100' C. The contents were poured into methanol and the precipitated, solid polymer was isolated. The polymer was purified b>- precipitation from acetone solution by methanol. -4nalysis: Calculated for 3,3,3-trichloro-l -propenevinyl acetate: C1, 48.9. Calculated for 3,3,3-trichloro-l-propene-2 vinyl acetate: C1, 36.8. Found: C1, 37.8. The copolymer would not support combustion. 3,3,3-Trichloro-l-propene(3.0 grams, 0.021 mole), methylmethacrylate (3.0 grams, 0.03 mole), and 310 mg. of benzoyl peroxide were added to a polymerization vial, the contents frozen, evacuated, and then heated at 100' C. for 7 hours. The solution was poured into methanol to precipitate the polymer. Analysis: Calculated for 3,3,3-trichloro-1-propene-12 methyl methacrylate: C1,7.80. Found: C1, 7.89. Attempts to polymerize 1,1,3-trichloro1-propene using diacetyl peroxide failed to produce any polymer.
Discussion The literature relating to the synthesis of 3,3,3-trichloro-l -propene is confusing. Kharasch ( 3 ) reported the preparation of 3,3,3-trichloro-l-propeneby dehydration of 1-methyl-2,2,2-trichloroethanol with phosphorus pentoxide. Two major products were isolated : boiling point 52' to 55' C. (103 mm.) n% 1.4680; and boiling point 57' C. (103 mm.) ny 1.4827. Kharasch believed the 1.4827, to be second compound, n? 3,3,3-trichloro-l-propeneand the lower boiling material to be 1,l-dichloroallene, Attempts to add hydrogen chloride or hydrogen bromide to the second compound led to failure or low yields of adducts. Hodnett (2) prepared l,l,l-trichloro3-bromopropane in 42% yield from the benzoyl peroxide-catalyzed addition of bromotrichloromethane to ethylene. Attempts to prepare 3,3,3-trichloro-lpropene from 1,l,l-trichloro-3-bromo-
INDUSTRIAL AND ENGINEERING CHEMISTRY
propane using triethylamine, diethylaniline, or alcoholic potassium hydroxide all failed. Freidlina ( 7 ) prepared 3,3,3-trichloro1-propene by dehydrochlorination of 1,1,1,3-tetrachloropropane, using alcoholic potassium hydroxide. The boiling point reported was 44' to 45' C. (103 mm.) with nF 1.4680. This material was found to isomerize to 1,1,3trichloro-1-propene upon heating to 150' C. The latter material boiled at 74' to 75' C. (103 mm.) with n T 1.4960. The structures of these were proved by ozonolysis and hydrolysis of the ozonides. The second product of Kharasch undoubtedly was not 3>3,3-trichloro-lpropene. Nesmeyanov ( 4 ) reviews the Russian work on these compounds and reports that 3,3,3-trichloro-l-propeneis not inert, as reported by Kharasch, but undergoes allylic rearrangement readily, adds chlorine, bromine. and hydrogen bromide, and condenses with benzene in the presence of aluminum chloride. The results of this article agree well with those reported by the Russian workers and support their viewpoint that Kharasch's second compound was not 3.3,3-trichloro-l-propene.The prep3.3,3-trichloro-l-propene aration of from 1,l ,l-trichloro-3-bromopropane does not give as large a yield of the byproduct, 1.1,3-trichloro-l-propene, as does the dehydrochlorination of 1,1,1.3tetrachloropropane. The availability of 3,3,3-trichloro-lpropene from ethylene and bromotrichloromethane as raw materials will undoubtedly stimulate interest in its use as a flame-retarding component in many vinyl polymers.
Acknowiedgmenf The authors express their appreciation to the Ethyl Corp. and Stanford Research Institute's Physical Sciences Divisional Research Committee for the support of this research and to Oliver Smith of the Analytical Chemistry Department of Stanford Research Institute for the chloride analyses.
literature Cited (1) Freidlina, R. Kh., Firstov, V. I., Akad. hTauk. S.S.S.R., Inst. Org. Khim., Sintezy Org. Soedinenir, Sbornik 2, 134 (1952). (2) Hodnett, E. M., Schnitzer, A. M., Proc. Oklahoma Acad. Sci.32, 94 (1951). ( 3 ) Kharasch, M. S., Rossin, E. H., Fields. E. K., J . A m . Chcm. SOL.63, 2558 ( 1 9 4 1 ) . ( 4 ) Nesmeyanov, A. N., others, Quart. Reus. (London) IO, No. 3, 330 (1956). ( 5 ) Skinner, W. A., Bishop, Ernest, Tieszen, Dale, Johnston, J. D., J . Org. Chem. 2 3 , 1 7 1 0 (1958).
RECEIVED for review April 2 1959 ACCEPTEDJuly 16, 1959
Division of Organic Chemistry, 135th Meeting, ACS, Boston, Mass., April 1959.
