Chemical reactions involved in penicillin allergy: kinetics and mechanism of penicillin aminolysis

Abstract

Abstract In view of the fundamental importance of the reaction of penicillins with amino groups of proteins to the penicillin allergy, the aminolysis of benzylpenicillin by various amines was kinetically investigated. The formation rate constants, kamide, of benzylpenicilloylamides were determined at 35°, 45° and 60° (μ = 0·5), and found to obey the general rate law: kamide = k1[amine] + k2[amine H+] [amine] + k3[amine]2 + k4[amine]aOH. All of the amines exhibited the unassisted nucleophilic rate constant, k1. The relative importance of the other kinetic terms depends on the basicity and the chemical structure of amines. The reaction mechanism of penicillin aminolysis was discussed. Brønsted relations for k1, k2 and k3, except for hydrazines, were satisfactory.