Benzyl Chloride, Benzal Chloride, and Benzotrichloride

Abstract

When toluene reacts with chlorine under experimental conditions that promote free‐radical chlorination, a mixture of benzyl chloride, benzal chloride, and benzotrichloride is obtained. The product distribution is determined in large part by the chlorine:toluene ratio. Competing reactions result in chlorination of the aromatic ring, reducing the yield of side‐chain chlorination products. Benzyl chloride undergoes reactions typical of a reactive alkyl halide. Hydrolysis gives benzyl alcohol, reaction with ammonia yields benzylamines, and benzyl esters form by reaction with salts of carboxylic acids. Reaction with other nucleophiles yield substitution products; alkoxides give benzyl ethers and cyanide give phenylacetonitrile. Benzal chloride is hydrolyzed to benzaldehyde and benzotrichloride to benzoic acid. Benzotrifluoride is formed by the reaction of benzotrichloride with anhydrous hydrogen fluoride. Reaction conditions have been determined for aromatic ring chlorination and nitration of benzyl chloride, benzal chloride, and benzotrichloride. More than two‐thirds of benzyl chloride produced is used to make the plasticizer benzyl butyl phthalate. Nearly all of the benzal chloride produced is consumed in the manufacture of benzaldehyde. Benzotrichloride is used in the manufacture of benzoyl chloride and in the synthesis of the herbicide intermediate p ‐chlorobenzotrifluoride.