Kinetics of racemization and hydrolysis of oxazol-5(4H)-ones

Abstract

The kinetics of hydrolysis and ionization of three substrates, 4-benzyl-2-phenyl-, 4-methyl-2-phenyl-′ and 4-benzyl-2-methyl-oxazol-5(4H)-one have been investigated. Under neutral and basic conditions, both reactions are buffer and hydroxide ion catalysed. In aqueous solution, ionization, leading to racemization of the optically active oxazolones, and ring opening occur competitively with similar rate constants. In solvents with lower dielectric constants, ionization becomes much faster than ring opening. An intermediate corresponding to a minor reaction pathway has been detected; it results probably from the addition of water to the C–N double bond.