Mechanism for partial oxidation of Cyclohexene by Chromium (VI) oxide in acetic acid

Abstract

The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media was studied. The reaction products were analysed using infra red (IR) and gas chromatography coupled with mass (GC/MS) spectroscopy. The major products of the oxidation reaction in acetic acid medium were cyclohexanol, cyclohexanone, 2-cyclohexen-1-one, 1,2-cyclohexanediol monoacetate and Bi-2-cyclohexen-1-yl. However, no reaction was observed between cyclohexane and chromium (VI) oxide in the aqueous medium. Based on the results a mechanism for the oxidation reactions was been proposed involving dissociation of acetic acid to form an acetate anion, which attacked the chromium (VI) oxide to form an acetochromate ion. The latter compound attacked cyclohexane to
form acetochromate cyclohexenyl ion intermediate, which undergoes electron shift and rearrangement to produce cyclohexanone and chromium (IV) oxide, thereby regenerating the acid. In the proposed mechanism, acetic acid serves both as homogeneous catalyst and medium for the
reaction.

Keywords: Cyclohexene, chromium (VI) oxide, acetic acid, oxidation