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 has been studied. The reaction products were analysed using classical method, IR and GC/MS analyses. The major products of the oxidation reaction in acetic acid medium are cyclohexanol, cyclohexanone, cyclohex-2-en-1-one, cyclohexan-1,2-diol monoacetate and  Bi-2-cyclohexen-1-yl. However, no reaction was observed between cyclohexene and chromium (VI) oxide in aqueous medium. Based on the result a mechanism for the oxidation reactions has been proposed involving dissociation of acetic acid to form an acetate anion which attacks the chromium (VI) oxide to form an acetochromate ion. The latter then attacks cyclohexene to form an acetochromate cyclohexenyl ion intermediate which undergoes electron shift and rearrangement to produce cyclohexanone and chromium (IV) oxide, thereby regenerating the acid. The proposed mechanism suggests that the acetic acid serves both as homogeneous catalyst as well as medium for the reaction.