Kinetics of Oxidation of Substituted Benzaldehydes by Acid Bromate

Department of Chemistry, Guru Nanak College, Madras-600 082 Department of Chemistry, Madras Christian College, Madras-600 069 Manuscript received 11 October 1983, revised 30 October 1984, accepted 15 February 1985 The kinetics of oxidation of benzaldehyde and some substituted benzaldehydes (o-CI, m-CI, p-Cl, o-F, m-F and p-F) have been investigated in aqueous acetic acid medium in the presence of sulphuric acid. The reaction exhibits first order both in substrate and oxidant, and second order in hydrogen ion. The reaction at constant excess H+ follows the rate expression, \(\frac{-d[Br(V)]}{dt}\)=k [Br(V)] [aldehyde]. The rate of the reaction increases with increasing acetic acid content of the medium. The order of reactivity of substituted benzaldehyde is, m-CI > m-F > o-CI > p-Cl > o-F > H> p-F. the rho value is +1.1. A mechanism involving rate-determining formation of a bromate ester which decomposes to products in a fast step has been proposed