Kinetics of hydrolysis and aminolysis of 1-methoxycarbonylpyridinium ions

Abstract

Rate constants are reported for reactions of 1-methoxycarbonylpyridinium ions in aqueous solution with water, hydroxide ion, and primary and secondary amines. The water reaction is general base-catalysed; solvent isotope effects are reported. Both the water and hydroxide reactions proceed with rate-determining formation of a tetrahedral intermediate. With the primary and secondary amines, either formation or breakdown of a tetrahedral intermediate is rate-determining, depending upon the ring substituent. Structure–reactivity plots lead to estimates of relative leaving-group abilities, which are compared with others in the literature. Hydroxide-ion catalysed aminolysis is observed in some cases, and occurs by a concerted mechanism.