β-Ureido-acids and dihydrouracils. Part IX. Kinetics and mechanism of alkaline hydrolysis of dihydrouracils

Abstract

The kinetics of alkaline hydrolysis of dihydrouracils are of the first and second order in hydroxide ion, reverting to first (apparent zero) order at high alkalinity. The reaction is general base-catalysed. A mechanism is suggested involving reaction only of the un-ionised species with rate-determining general base-catalysis by water and decomposition by hydroxide ion of the tetrahedral addition intermediate changing to rate-determining formation of the addition intermediate at high alkalinities.