Mechanistic &; Reactivity of Aromatic Anils : Cooxidation Mechanism of Aromatic Anils and Oxalic Acid by Chromic Acid in Aqueous Acetic Acid Medium

Chromic acid [Cr(VI)] is an important and useful tool in the hands of chemists both for preparative and analytical purposes .It has been used to oxidize almost all organic and some inorganic compounds. Aromatic anils and substituted aromatic anils were prepared, characterized and the cooxidation of aromatic anils and oxalic acid by chromic acid in aqueous acetic acid medium proceeds much faster than that of either of the two substrates alone.The rate of the reaction increases when electron-releasing groups introduced on one ring or both rings of the anils whereas,electron-withdrawing groups decreasing the rate of oxidation at the same manner. The oxidation kinetics of aromatic anils by Cr(VI) in presence of oxalic acid in aqueous acetic acid follows first order in [oxidant] and fractional order in [substrate] and [oxalic acid] with the corresponding yields benzaldehyde and azobenzene. The rate of oxidation is enhanced with increasing concentration of hydrogen ions.Aluminium ions suppress the reaction. The intermediate is believed to be formed from aromatic anils and chromic acid-oxalic acid complex.Thus, this is a suitable mechanism proposed for the cooxidation reaction.