INTRAMOLECULAR GENERAL-BASE CATALYSIS OF SCHIFF-BASED HYDROLYSIS BY TERTIARY AMINO GROUPS.

Article abstract of DOI:10.1021/ja00367a016

Hydrolysis of a series of Schiff bases derived from benzophenone and various amines has been studied kineticlly in aqueous solution. A linear correlation of the log of the rate constants for the water reaction with the Schiff base pK//a (slope minus 0. 70) shows large positive deviations for Schiff bases derived from (2-aminoethyl)diethylamine, N-(2-aminoethyl)morpholine, N-(2-aminoethyl)piperazine and 2-(aminomethyl)pyridine (1i) but small deviations for Schiff bases from N-(3-aminopropyl)morpholine and 2-(2-aminoethyl)pyridine. The deviations found are attributed to intramolecular general-base catalysis of the water reaction by the internal tertiary amino groups. Magnitudes of the rate enhancement are correlated well with pK//a//l of the internal catalyst ( beta equals 0. 49). Effective concentrations of the internal bases are estimated to range from 340 (1e) to 40 M.