The solvolysis of 2-trimethylsilylpyridine by alcohols and by water

Abstract

2-Trimethylsilylpyridine, unlike the 3- and 4-isomers, reacts with water, methanol, or ethanol to give pyridine and trimethylsilanol or the alkoxytrimethylsilane. The relative rates of reaction are 740, 120, and 1 in water, methanol, and ethanol respectively. No detectable reaction occurs with higher alcohols. Acids inhibit the reaction, and bases have very little effect. These solvolyses have small activation enthalpies and high negative activation entropies, and the solvent isotope effect is very small. The most likely reaction mechanism involves rate-determining attack on the silicon by the oxygen of the hydrogen-bonded solvent, i.e. nucleophilic substitution with electrophilic assistance via a 5-centred cyclic activated complex.