Reactions of organic phosphates. Part VI. The hydrolysis of aryl phosphates

Abstract

The hydrolysis of monoaryl phosphates shows acid catalysis only if an electron-attracting substituent (e.g., NO₂–or CH₃CO–) is present in the aryl group. There is then a rate maximum at a strong acid concentration in the range 3–6M. A typical rate maximum at ca. pH 4·0 due to hydrolysis via the monoanion species is observed in all cases. The reactions, both in aqueous strong acid and at pH 4, proceed by phosphorus–oxygen bond fission.

Rate maxima in aqueous strong acid are also observed in the hydrolysis of diphenyl and triphenyl phosphates: the reactions also proceed by phosphorus–oxygen bond fission. The maxima do not arise from complete protonation of the substrate but are apparently the result of a powerful negative electrolyte effect.