Benzyl ethers are often derived from benzyl chloride. Benzyl chloride was first prepared from treatment of benzyl alcohol with hydrochloric acid. Benzyl alcohol is subsequently metabolized to benzoic acid. The reaction works well for methyl, benzyl, and phenyl substituents. It is the ester of benzyl alcohol and benzoic acid. It is rapidly hydrolyzed to benzoic acid and benzyl alcohol. Molecules that can form allyl or benzyl carbocations are especially reactive. Contact lens solutions often contain preservatives such as benzalkonium chloride and benzyl alcohol. Benzaldehyde reacts with sodium benzyloxide (generated from sodium and benzyl alcohol) to generate benzyl benzoate. An early method for production of benzoyl chloride involved chlorination of benzyl alcohol. Newer generic formulations contain sodium metabisulfite or benzyl alcohol as antimicrobial agents. The ketone is then reduced with sodium borohydride yielding a benzyl alcohol. It is formed by the condensation of benzyl alcohol and acetic acid. Benzyl benzoate was first studied medically in 1918. Other functional groups, such as benzyl ethers, can also be oxidized by ozone.