Chloraminometric reactions: kinetics and mechanisms of oxidations of amino-acids by sodium N-chlorotoluene-p-sulphonamide in acid and alkaline media

Abstract

Available data on the kinetics of oxidations of amino-acids by sodium N-chloro toluene-p-sulphonamide (chloramine T) in acid and alkaline media have been critically examined. General mechanisms have been proposed for both acid and alkaline medium oxidations. The oxidation process in acid media has been shown to proceed via two paths, one involving the direct interaction of N-chlorotoluene-p-sulphonamide (RNHCl) with the neutral amino-acid in a slow step leading to the formation of the monochloroamino acid which subsequently interacts with another molecule of RNHCl, in a fast step, to give the NN-dichloroamino-acid which in turn undergoes molecular rearrangement and elimination to yield the products, and the other involving the interaction of Cl₂ or H₂OCl⁺, produced from the disproportionation of RNHCl in the presence or absence of Cl^–, with the substrate to give the products. In the alkaline medium mechanisms involving the interaction of RNHCl, HOCl, RNCl^–, and OCl^– with the substrate are proposed. The mechanisms proposed and the derived rate laws are consistent with the observed kinetics. The rate constants predicted by the derived rate laws, as the concentrations of substrate and Cl^– ion change, are in excellent agreement with the observed rate constants thus further verifying the rate laws and hence the proposed mechanisms.