Kinetics and mechanism of the alkaline hydrolysis of maleimide.

The kinetics of hydrolysis of maleimide was carried out within the [OH-] range of 2.46 X 10(-6) to 2.0 M at 30 degrees C. The observed pseudo-first-order rate constants, kobs, follow the empirical equation: kobs = (A1[OH-] + A2[OH-]2)/(1 + A3[OH-]). Both ionized and un-ionized forms of maleimide have been suggested to be involved in hydrolysis. The nucleophilic attacks by hydroxide ion at the carbonyl carbon of both ionized and un-ionized maleimide and by water at the carbonyl carbon of ionized maleimide to form tetrahedral intermediates are considered to be the rate-determining steps. The observed results obtained at different 1,4-dioxane-water compositions have revealed an increase in kobs with a decrease in 1,4-dioxane content which could be attributed to the higher polarity of the transition state compared with the reactant state.