2, 2'-Bipyridyl Catalysis of the Chromium (VI) Oxidation of 1, 2-propanediol: a Kinetic and Mechanistic Study

The kinetics and mechanism of 2 , ′-bipyridyl (bpy) catalysis of the chromium(VI) oxidation of 1, 2-propanediol in aqueous acidic medium has been studied spectrophotometrically. The reaction shows pseudo-first order with respect to Cr(VI) and fractional order with respect to 1 , 2-propanediol. The observed rate constant ( kobs) increases with the increase in [H +] and [bpy]. Change in ionic strength does not influence the rate obviously and no free radicals are detected. Thus, HCrO 4 is assumed the main existing species of Cr(VI). Based on the experimental results, a probable reaction mechanism of oxidation is proposed. The rate equation derived from the mechanism can explain all the experimental phenomena. The activation parameters along with rate constants of the rate-determining step have been calculated.