A mechanistic investigation of the oxidation of N, α-diphenylnitrones by dichloramine-T in aqueous acetonitrile medium - a non-linear Hammett plot

摘要

The kinetics of oxidation of a number of meta-and para-substituted N, α-diphenylnitrones (nitrone) by dichloramine-T (DCT) was investigated in the presence of alkali in aqueous acetonitrile medium. The order with respect to DCT was one and to OH~- an inverse fractional order. The reaction was first order with respect to nitrone. Both electron releasing and withdrawing substi-tuents suppress the reaction rate. The observed rate constant for the substituents were plotted against the Hammett constant, σ, and a non-linear concave downward curve was obtained. The electron withdrawing substituents fall on one side of the curve, having a negative ρ value and the electron releasing substituents fall on the other side, with a positive ρ value. A mechanism is proposed and the derived rate law is in conformity with the observed results.