Oxidation of ascorbic acid by hexacyanoferrate(III) in aqueous perchloric acid medium-A kinetic and mechanistic study

Laxmi Jattinagoudar, Kirthi Byadagi, Noorjahan Shirhatti, Sharanappa Nandibewoor, Shivamurti Chimatadar
2013 Journal of Chemical and Pharmaceutical Research   unpublished
The oxidation of ascorbic acid (H 2 A) by hexacyanoferrate(III)(HCF) in aqueous perchloric acid medium at a constant ionic strength of (0.6 mol dm-3) was studied spectrophometrically at 25 o C. Reactions were initiated by mixing previously thermostated solutions of hexacyanoferrate(III) and ascorbic acid which also contained the required amounts of perchloric acid and sodium perchlorate. The kinetics were followed under pseudo first order conditions with ascorbic acid in excess. The reaction
more » ... ss. The reaction between hexacyanoferrate(III) and ascorbic acid in acidic medium exhibits 2:1 stoichiometry. The reaction products were identified and isolated using TLC separation techniques and characterized by IR, and GCMS spectral studies. The reaction is first order with respect to hexacyanoferrate(III) and ascorbic acid concentrations. The order with respect to acid concentration is less than unity. The effect of ionic strength and dielectric constants are also studied on the rate of reaction. A suitable mechanism is proposed based on the experimental results. The reaction constants involved in the different steps of the reaction mechanism are calculated. The activation parameters with respect to limiting step of the mechanism are computed and discussed.