Ru(III)-catalysed oxidation of some N-heterocycles by chloramine-T in hydrochloric acid medium: a kinetic and mechanistic study

The following general scheme is proposed for the Ru(III)-catalysed oxidation of N-heterocycles by chloramine-T in acid medium to explain the experimental results:(i)TsNHCl+H3O+⇌K1TsNH2+H2O+Clfast(ii)S+nH2O+Cl⇌K2Xfast(iii)X+Ru(III)⇌K3X′fast(iv)X′⟶k4productsslow and r.d.sHere n = 3 for imidazole, 2 for benzimidazole and 1 for 2-hydroxybenzimidazole, 2-aminobenzimidazole and 2-phenylbenzimidazole. S, X and X′ represents the substrate and complex intermediate species. The above scheme leads to the following rate law:rate=K1K2K3k4[CAT]t[S][H3O+][Ru(III)][TsNH2]+K1[H3O+]+K1K2[S][H3O+]+K1K2K3[S][H3O+][Ru(III)]