MECHANISTICALLY OPTIMIZED INTRAMOLECULAR CATALYSIS IN THE HYDROLYSIS OF ESTERS - GLOBAL CHANGES INVOLVED IN MOLECULAR REACTIVITY

The hydrolysis of the 2',2',2'-trifiuoroethyl monoester of 1,8-naphtha lic acid (1) proceeds via the monoanion with the intermediate formatio n of the corresponding anhydride. The rate constant for the formation of 1,8-naphthalic anhydride (2) is ca 2500 times faster than its rate of hydrolysis. The Isotope effect in the plateau region and theoretica l calculations at the PM3 level suggest that elimination of the alkoxi de is the rate-limiting step for the reaction. Accordingly, decomposit ion of the isopropyl monoester of naphthalic acid proceeds 10(4) times slower than the spontaneous decomposition of 1. The remarkably high r ate of monoester decomposition derives from the special configuration of the substrates and important contributions that arise from relief o f torsional strain, which clearly includes electron redistribution due to the decrease in steric hindrance to resonance and the fact that pr oximity obviates solvation. (C) 1997 by John Wiley & Sons, Ltd.