Kinetics of oxidation of <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-ascorbic acid by iron(III) in presence of 2,2'-bipyridyl-Application of Marcus theory

Abstract

Kinetics of oxidation of ascorbic acid by iron(III) in the presence of 2,2'-bipyridyl has been investigated under anaerobic conditions. The reaction is first order each in [iron(III)] and [ascorbic acid]. The plots of 1/<em>k</em>’ versus 1/[Bipy]<img src="http://www.niscair.res.in/jinfo/equation165.gif" alt="" border="0" /> and 1<em>/k' </em>versus [H⁺]² are linear with positive intercepts. The kinetic results provide evidence for the formation of an intermediate complex, Fe(bipy) <img src='http://www.niscair.res.in/jinfo/equation28.gif' border=0> which reacts with the unionised form of ascorbic acid in the rate-limiting stage. The stability constant of the complex has been evaluated from the kinetic data. The kinetic data are compatible with the Marcus' theory for outer sphere electron-transfer.