Kinetics and mechanism of reduction of p-nitroso-N,N-dimethylaniline by sulphite ions in acetate-acetic acid buffer solutions

Abstract

Kinetics of the title reduction has been studied spectrophotometricaJly in acetate-acetic acid buffer solutions at different temperatures in the range 20&deg; to 40&deg;c' The effect of varying [H⁺] on the reduction rate has been investigated at constant ionic strength 'Of0.06. The rate order is 1.0 in both the reactants and - 0.5 in [H⁺]. The rate of reaction decreases with increase in [H⁺]. The [H⁺] dependency indicates the presence of two competitive rate-determining steps. The activation parameters have been determined and found to be <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>S ^&ne; </em>= - 176.09 JK ^-1 mol^-1, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>H^&ne; </em>= 17.82 kJ mol^-1 and <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0>G<em>^&ne;</em> = 70.30 kJ mol^-1. A mechanism consistent with the experimental results has been suggested.