Kinetic study of the iodine‐catalyzed alcoholysis of Butoxytriethylsilane: n‐butoxy group—s‐butoxy group exchange reaction

Abstract

In order to appreciate the excellent catalytic effect of iodine on the alcoholyses of alkoxysilanes more precisely, the rates of the reaction, Et3SiOBun + BusOH ⇌ Et3SiOBus + BunOH, were determined at various iodine concentrations. Both forward and reverse reactions are first order with respect to butoxysilane and to butanol, and pseudo first‐order rate constants were measured at 40°, 30°, and 20°C on reaction mixtures containing both butanols in excess by means of gas‐liquid chromatography. The observed rate constants as a function of iodine concentration gave linear relationships, and from these data the catalytic coefficients of iodine were evaluated: The enthalpies and the entropies of activation were estimated to be 53.2 kJ mol−1, −103 J K−1 mol−1 (forward, 30°C) and 51.8 kJ mol−1, minus;100 J K−1 mol−1 (reverse, 30°C).