Kinetic Studies of the Triethylenediamine-catalyzed Transamidation of 1,3-Diphenylurea with n-Butylamine in Dioxane

Abstract The rates of the transamidation of 1,3-diphenylurea (abbreviated as DPU) with n-butylamine (BA) in dioxane in the presence of triethylenediamine (TED), forming n-butylphenylurea (BPU), aniline and carbon dioxide, were followed ultraviolet-spectrophotometrically. The rate of the reaction satisfied the following equation: υ={k1′+k2′[TED]}[DPU]+{k2″+k3[TED]}[BA][DPU]. The first and second terms correspond to the non- and the TED-catalyzed hydrolysis of diphenylurea, while the third and fourth terms represent, respectively, the non- and the TED-catalyzed transamidation. In both the non- and the TED-catalyzed transamidation, a probable mechanism which involves the nucleophilic attack of the lone pair of the N-atom on the carbonyl C-atom of diphenylurea, followed by the formation of ion pairs of quaternary ammonium salt and of quaternary ammonium type salt, was discussed.