US2602823A - Alpha-bromoethylpentachloro-benzene - Google Patents

Description

Patented July 8, 1952 ENTj-QFFHCE A ALPHA-BROMOETHYLPENTACHLORO- BEN ZENE Sidney D. Ross andMoushy Markarian, North Adams, and Mathew Nazzewski, Adams, Mass., assignors to Sprague Electric Company, North Adams, Mass., a corporation of Massachusetts No Drawing. Application'February 10, 1947, Serial No. 727,736

1 Claim.

This invention relates to new halogenated aromatic compounds and more particularly refers to bromoethyl pentachlorobenzene and its closely related derivatives.

An object of this invention is' to produce new alkyl substituted derivatives of polyhalogenated benzene. A further object is to produce new and useful halogenated derivatives of alkyl pentachlorobenzenes. A still further object is to produce new derivatives of ethylpentachlorobenzene by relatively simple processes. Additional objects will become apparent from the following description and claim.

These objects are attained in accordance with our invention which broadly is directedto a, class of compounds conforming to the general formula: 1

(Chew; n

wherein R, isa bromo-alkyl group, and. is an integer from 1 to 5.

In a, more restricteds'e'nse this invention is concerned with compounds conforming to the general f ormula wherein R is an alkyl group, preferably containingfrom two to four carbon atoms, and :1: is an integer from l to 5, preferably 1 or 2. i

The following tabulation includes representative compounds embraced within the scope of this invention:

beta tribromoethylpentachlorobenzene compound; I

Beta, beta, beta" tribromoethylpentachlorobenzene 1,2 dibromo-2-pentachlorophenyl-propane 1,2 dibromo-1-pentachlorophenyl-propane- 1,3 dibromo-1-pentachlorophenyl propanel 3 2,3 dibromo-l-pentachlorophenyl-propane 1,3 dibromo-2-pentachlorophenyl-propane Pentachlorobenzylbromide= One of the preferred embodiments of the invention concerns monob'romo derivatives of ethyl pentachlorobenzene, specifically alphabromoethylpentachlorobenzene and betabromoethylpentachlorobenzene.

We have found that the compounds of this invention may be produced by processeswhich are simple and eflicient. The following examples are illustrative of these processes:

EXAMPLE 1 Prcpa'mtion of alphabromo ethylpemtachlorobenzene 2785 grams of ethylpentachlorobenzene were heated to -100" 0. in a three-necked flask, fitted with a dropping funnel, reflux condenser and a mechanical stirrer. A 200 watt unfrosted bulb was placed next to the hash and illuminated during the reaction. 159.8 grams of bromine were added slowly over a twelve-hour period. Hydrogen bromide was given off during the addition. The reaction mixture Was poured into an evaporating dish and evac'uated over potassium,hy-

droxide and calcium chloride. The crudeprodnot thus obtained weighed 325 grams and melted at"' 105'-1l5 C. r This represents a 90% yield of Recrystallization from acetone brought the melting point 'of the alphabromoethylpentachlorobenzene to"1 2 1-12'2 C. A' second recrystallization of this material brought the melting point to 123-124 I C. Carbon and hydrogen analyses performed upon the pure material confirmed the empirical formula.

. EXAMPLE 2 Preparation of alphabromoethylpefitacshlorobenzene I The procedure of Example 1 was followed with the exception that the temperature of the reacting material was maintained at'about1'40 C. and the time of'addition was. 2fl hours. There was obtained a 68% yield of thefalpha bromo 3 EXAMPLE 3 Preparation of ralphrabromoethylpentachlorobenzene The procedure of Example 1 was followedwith the exception that the temperature was maintained at 180 C. and the bromine added over a 6-hour period. A substantial yield of the alpha g bromo compound was obtained but the percent-- age was smaller than in Examples 1 and 2.

EXAMPLE 4 Preparation of alphabromoethylpertta'chlorobenzene 2 grams of methyl pentachlorophenyl carbinol,

a known compound prepared by the method of Gunther Lock, Ber. 72B, 1939, pp. 300-304, and

10 grams of 48% hydrobromic acid were refluxed for two hours, with an oil bath temperature of EXAMPLE 5 \betabromoethylpentachloro benzene 92.5 grams; (.5 mole) beta phenylethylbromide 2.5 grams AlCla 4.1 grams S2012 404 grams 802012 The beta phenylethylbromide and aluminum chloride were placed in a 50 cc. three-necked flask equipped with a reflux condenser, thermometer and dropping funnel. The sulfur chlo- Preparation of -ride and sulfuryl chloride mixture was run in slowly at room temperature. After a short time the, aluminum chloride dissolved and theevolution of hydrochloric acid began. The color changed to yellow, then brown and the temperature began to go up but was maintained below 60 C. by means of an ice bath until approximately one-half of the chlorinating mixture had been added. The temperature was then maintained at 60-64 C. by means of a heating mantle for the rest of the addition period and for one and one-quarter hours thereafter. The reaction mixture was allowed to stand at .room temperature over night and the reaction continued as evidenced by the evolution of hydrochloric acid. The next morning the mixture was melting from 88-95 C. The product was dissolved in 95% ethanol, with a separation of a small amount of tar and upon cooling crystals were deposited with a melting point of 96-98 C.

Upon recrystallization from a mixture ;of ace- 4 tone and alcohol there was obtained 84 grams of melting point 96.5-98" C. The mother liquor was worked up and a total yield of grams of betabromoethylpentachlorobenzene was obtained... Threerecrystallizations from acetone in alcohol brought the melting pointto 98-99 C. A mixed melting point with the material of Example 1 gave a highly depressed melting point indicating that these two compounds were not the same.'

EXAMPLE 6 Preparation of 1-pentachZorophenyl-1-aceto:cy-

' ethane 17.9 grams of the alphabromoethylpentachlorobenzene produced in Example 1 were refluxed with 19.6 grams of potassium acetate and 275 cc. of acetic acid for 20 hours. At the end of this time most of the acetic acid was removed with a water pump and the residue taken up in benzene and water. The benzene layer ,was separated and dried and subjected to distillation to remove most of the benzene. The residue was dissolved in acetone and water and the product crystallized therefrom to give a melting point of 90-95 C. Upon three recrystallizations' from methanol the pure acetoxycompound possessed a melting point of 101 102 'c. V

v EXAMPLE 7 v Preparation of methylpentachlorocarbinol 2 grams of the l-pentachlorophenyl-l-acetoxyethane produced in Example 6 were refluxed for four hours with 1 gram of potassium hydroxide dissolved in 25 cc. of water and cc. of acetone. At the end of this time most of the acetone was removed with a water pump vacuum and more water then added, giving a precipitate which when filtered and dried weighed 1.9 grams. This material possessed a melting point of l20.5-122 C. Upon recrystallization from methanol and water the melting point was raised to 124-125'C. A mixed melting point was made with the carbinol produced by Gunther Lock previously referred to, to give a melting point of 122-123" 0., indicating that these compounds are identical.

The bromination of ethylpentachlorobenzene is generally conducted in a temperature range from about 60 C. to about 200 0., although lower temperatures may be employed when a solvent for the ethylpentachlorobenzene is employed.

The ring chlorination of beta phenylethylbromide as described previouslyis advisably con- "ducted at'a low temperature to minimize the condensation reactions which may occur in the presence of aluminum chloride. The temperature is generally at'or below the reflux temperature of the chlorinating agents. Alternately the chlorination may be conducted with liquid or gaseous chlorine in the presence of iron.

Pentachlorobenzyl bromide may be prepared by low temperature ring chlorination of benzyl bromide or by bromination of pentachlorotoluene. The compounds of this invention may be used as intermediates in the formation of numerous organic compounds. They possess a very high flash point and will not sustain flame per se, and above their melting points are good solvents for aromatic and chlorinated compounds. As heat transfer agents they are likewise useful. Because the aliphatic bromine'is quite reactive, it is possible to use the compounds of the invention in a large number of useful reactions such as the Friedel-Crafts reaction, with aromatic compounds; dehydrohalogenation with caustic, etc.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof except as defined in the appended claim.

What we claim is: Alpha-bromoethylpentachlorobenzene, a solid possessing a melting point of 123-124 C.

SIDNEY D. ROSS. MOUSHY MARKARIAN. MATHEW NAZZEWSKI.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,174,513 7 Holt et a1 Oct. 3, 1939 2,193,823 Levine et al Mar. 19, 1940 2,21 ,099 Jones Aug. 20, 1940 10 2,296,614 Hearne Sept. 22, 1942