OXIDATION OF AROMATIC ALDEHYDES IN THE PRESENCE OF OXALIC ACID BY PYRAZINIUM CHLOROCHROMATE-A NON-LINEAR HAMMETT PLOT

摘要

The oxidation of benzaldehyde and several para-and me to-substituted benzaldehydes by pyrazinium chlorochromate has been studied in the presence of oxalic acid.The reaction follows fractional order kinetics each with respect to substrate and H~+and first order with respect to oxidant and oxalic acid.The rate of the reaction increases with increase in percentage of acetic acid.The reaction does not induce the polymerisation of acrylonitrile.The rate of the reaction decreases with increase in the concentration of Mn(II).Both electron-withdrawing and electron-releasing substituents enhance the rate of the reaction and the Hammett plot shows a V-shaped curve.The products of the oxidation are the corresponding benzoic acids.The thermodynamic parameters are calculated and a probable mechanism has been proposed.