CS240391B1 - Method of benzylbromide preparation - Google Patents

Abstract

Process for preparing benzyl bromide by reaction with toluene with bromine, is present radical reaction catalysts, in the presence an oxidizing agent such as chlorine or sulfuryl chloride. The solution can be used in chemical industry.

Description

The invention relates to a process for the preparation of benzyl bromide by reacting toluene with bromine in the presence of an oxidizing agent such as sulfuryl chloride or chlorine. The compound can be used as an intermediate in the preparation of herbicides and growth regulators.

Bromomethylation of benzene by reaction with paraformaldehyde and sodium bromide in acetic and sulfuric acid is described in the literature to give benzyl bromide in 86% yield [Monatshefte fur Chemie 81, 917 (1950)], similar to the preparation of benzyl bromide where parafermaldehyde is substituted uses urotropin [Izv. higher, teaching. CLOSE. Chimii and Cimii Tech. 5, 505 (962)].

Methods for preparing benzyl bromide by radiation bromination of toluene in 90% yield (U.S. Pat. No. 119,713), reaction of toluene with bromine under direct sunlight or under artificial light at room temperature to reflection in an organic solvent such as CCli and CSz are described below. or without solvent [Chem. Ber. 18, 606 (1885); J. Am. Chem. Soc. 62, 3252 (1940), J. Am. Chem. Soc. 85, 365 (1963)].

Methods for preparing benzyl bromide by reacting toluene with bromine under the catalytic action of various types of peroxides, such as dibenzoyl peroxide, 1,1‘-azobisbutyronitrile, ascaridol, and others, are also known from the literature [J. Am. Chem. Soc. 59, 1405 (1937); J. org. Chem. 3, 33 (1938), Rec. trav. chim. 26, 1 (1907)].

It is known that in the reaction of toluene with N-bromosuccinimide, bromination occurs exclusively in the side chain, with the catalytic effect of light or peroxides producing benzyl bromide in about 70% yield [Helv. Chim. Acta 29, 573 (1946); Bull. Soc. Chim. Belges 59: 193 (1951), Acta acad. Absensis Wath. et Phys. 18, No 7 (1952)], with similar intent, N-bromoperfluorosuccinimide was used for brominating toluene [J. Am. Chem. Soc. 73, 1103 (1951)], or N-bromoacetamide [J. Am. Chem. Soc. 74, 2189 (1952)].

A disadvantage of the previously known processes for the preparation of benzyl bromide by bromination of toluene with bromine or its compounds was the low yield of the reaction, since half of the bromine is hydrogen bromide.

It has now been found that the above drawbacks overcome the process for preparing benzyl bromide by reacting toluene with bromine, optionally in the presence of radical reaction catalysts such as sunlight or artificial light, dibenzoyl peroxide, 1,1'-azobisformamide, 1,1'-azobisbutyronitrile according to the invention.

The principle of the invention is that the reaction of toluene with bromine is carried out in the presence of an oxidizing agent such as chlorine or sulfuric chloride in a molar ratio of 1.0: 0.8 to 1.0 at a temperature of 35 to 110 ° C.

Hydrogen chloride, r.p. a mixture of hydrogen chloride and sulfur dioxide and in addition to benzyl bromide, as well as minor amounts of benzyl chloride, usually 1 to 6%, which can be separated from the product by rectification.

The advantage of this process is that, in the presence of an oxidizing agent, the hydrogen bromide formed in the reaction is converted again to bromine, which in turn reacts with toluene. The use of bromine is doubled compared to the known methods.

The following examples illustrate but do not limit the scope of the invention. EXAMPLE

To 184 g of anhydrous toluene was added 0.5 g of bromine, and the reaction mixture was heated to decolorization with stirring. Under vigorous stirring, a mixture of 78.6 g of bromine and 66.2 g of sulfuryl chloride at 65 ° C was metered under the reaction mixture at a rate such that the bromine introduced could react. The addition took about 40 min. The reaction mixture was cooled and washed with water, 5% sodium bicarbonate solution and again with water and dried over anhydrous CaCl 2. Analysis of the crude reaction mixture by gas chromatography showed that it contained 62.9% benzyl bromide and 2.6% benzyl chloride in toluene.

Distillation yielded 157.2 g of benzyl bromide, which corresponds to an 89.2% yield (calculated on the bromine used).

Example 1 a d 2

Following the procedure of Example 1, a mixture of 80.1 g of bromine and 67.5 g of sulfuryl chloride was added to 184 g of anhydrous toluene at 50 ° C. After the addition was complete, the reaction mixture was heated to vigorous stirring with vigorous stirring to remove the resulting hydrogen chloride and sulfur dioxide. Analysis of the reaction mixture revealed that it contained 60.4% benzyl bromide and 3.3% benzyl chloride. The yield of benzyl bromide after distillation was 85.2% (calculated on the bromine used).

EXAMPLE 1 a d 3

Following the procedure of Example 1, 184 g of anhydrous toluene was thickened with a mixture of 80.0 g of bromine and 67.5 g of sulfuryl chloride at 35 ° C under a 100 W light bulb. 232 g of a reaction mixture containing 62.3% of benzyl bromide and 2.5% of benzyl chloride were obtained. After distillation, 144.5 g of benzyl bromide was obtained, corresponding to an 84.5% yield (calculated on the brgm used). The reaction gave benzyl bromide and benzyl chloride in a ratio of 25: 1.

example

Following the procedure of Example 1, 184.0 g of anhydrous toluene was treated with a mixture of 80.0 g of bromine and 67.5 g of sulfuryl chloride at ° C in the presence of dibenzoyl peroxide as a catalyst. 146.9 g were obtained, corresponding to an 85.9% yield (calculated on the bromine used).

Example 5

A cooled mixture of 159.8 g of bromine and 134 g of sulfuryl chloride was added below the surface to 300 g of anhydrous toluene at 80 ° C and vigorous stirring. After the addition was complete, toluene was distilled off from the reaction mixture and benzyl bromide was further distilled off. 221.5 g of product was obtained, which is 64.8% yield. The reaction produced 21.4 g of benzyl chloride. The ratio of benzyl bromide to benzyl chloride formed was 10.3: 1.

Example 5

To 485 g of azeotropically dried toluene, 329 g of bromine and 225 g of sulfuryl chloride were added simultaneously from two dropping funnels at 40 ° C and vigorous stirring for 3.5 hours. After completion of the reaction, the mixture was cooled, washed with water, 5% sodium bicarbonate solution and once more with water. After drying with anhydrous calcium chloride, the mixture was distilled. Distillation yielded 510 g of benzyl bromide with m.p. in. = 95 ° C / 3.9 kPa, which corresponds to 71.2% yield.

Example 1 and d 6

To 180 g of anhydrous toluene were added 2 drops of bromine and the mixture was heated to 60 ° C and stirred vigorously. After the initial initiation of the reaction, 79 g of bromine was added to the reaction mixture over a period of 1.5 hours, while chlorine was introduced into the reaction mixture at a rate of 0.3 g / min. Upon completion of the bromine addition, the chlorine feed was also terminated and the mixture was heated to 100 ° C, then washed with water, 5% aqueous sodium bicarbonate solution and dried over anhydrous calcium chloride. Distillation yielded 149.3 g of benzyl bromide, which corresponds to an 88.3% yield (calculated on the bromine used). Gas chromatography was determined to contain 3.8% benzyl chloride.

Claims (1)

SUBJECT A process for the preparation of benzyl bromide by the reaction of toluene with bromine, optionally in the presence of a radical reaction catalyst, characterized in that toluene is reacted with bromine to form a OF THE INVENTION the presence of an oxidizing agent such as chlorine or sulfuryl chloride in a molar ratio of 1.0: 0.8 to 1.0 relative to each other at a temperature of 35 to 110 ° C.