Benzene
DETAIL
Preparation
Benzyl chloride is prepared industrially by the gas-phase photochemical reaction of toluene with chlorine:
The reaction proceeds by the free radical process, involving the intermediacy of free chlorine atoms. Side products of the reaction include benzal chloride and benzotrichloride.
Other methods of production exist, such as the Blanc chloromethylation of benzene. Benzyl chloride was first prepared from treatment of benzyl alcohol with hydrochloric acid.
Uses and reactions
Industrially, benzyl chloride is the precursor to benzyl esters, which are used as plasticizers, flavorants, and perfumes. Phenylacetic acid, a precursor to pharmaceuticals, is produced from benzyl cyanide, which in turn is generated by treatment of benzyl chloride with sodium cyanide. Quaternary ammonium salts, used as surfactants, are readily formed by alkylation of tertiary amines with benzyl chloride.
Benzyl ethers are often derived from benzyl chloride. Benzyl chloride reacts with aqueous sodium hydroxide to give dibenzyl ether. In organic synthesis, benzyl chloride is used to introduce the benzyl protecting group in reaction with alcohols, yielding the corresponding benzyl ether, carboxylic acids, and benzyl ester.
Benzyl chloride also reacts readily with metallic magnesium to produce a Grignard reagent. It is preferable over benzyl bromide for the preparation of this reagent, since the reaction of the bromide with magnesium tends to form the Wurtz coupling product 1,2-diphenylethane.