GENERAL ACID CATALYSIS OF KETAL HYDROLYSIS . HYDROLYSIS OF TROPONE DIETHYL KETAL

The hydrolysis of tropone diethyl ketal has been studied in water at 15˚. A pronounced general acid catalysis by the acid species of the buffer can be observed. The rate constant for catalysis by Tris (H+) is less in D2O than H2O (Kda/Kha = 0.67). The mechanism undoubtedly involves partially rate-determining protonation by the general acid. Thus, if the carbonium-ion intermediate is of great stability general acid catalysis can be obtained even with ketals of aliphatic alcohols. At pH values greater than 10 the rate of hydrolysis is independent of pH. This pH-independent reaction has a D2O solvent isotope effect (kD/kH) of 0.86. © 1969, American Chemical Society. All rights reserved.