Degradation of 1,3-diaryl-1-nitrosoureas in aqueous solutions and in organic solvents.

Abstract

The degradation of 1, 3-di (p, p'-disubstituted) aryl-1-nitrosoureas (I) in aqueous buffer solutions (at 0 °C over pH-0.5 to 5.4) and in several organic solvents (benzene, chloroform, etc.) has been kinetically studied. In aqueous solution, the overall rates of degradation followed pseudo-first-order kinetics at constant pH. The decomposition reaction of 1, 3-diphenyl-1-nitrosourea (Ia) was first-order in hydrogen ion over the pH range of-0.5 to 1.5 and denitrosated 1, 3-diphenylurea (IIa) was formed predominantly. In the range of pH 1.5 to 5.4, the degradation of Ia was catalyzed by hydroxide ion and the main product was IIa, which was formed by the recombination of reactive products. In organic solvents, thermal degradation of Ia obeyed first-order kinetics and gave similar products to those yielded in the base-catalyzed degradation. The acid-and base-catalyzed and thermal degradations of Ia were about 102 to 103 times more rapid than those of related 1, 3-dialkyl-1-nitrosoureas. The reaction mechanisms are discussed.