Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by (C9H7NH)2Cr2O7

Abstract

The Cr(VI)-quinoline complex[(C9H7NH)2Cr2O7] was synthesized by reacting C9H7N and CrO3" The structure of the product was characterized with infrared spectroscopy and elemental analysis. The oxidation of alcohols was examined by (C9H7NH)2Cr2O7 in [DMF]N,N-dimethylformamide, acetone. As a result, (C9H7NH)2Cr2O7 was found as efficient oxidizing agent that converted benzyl alcohol, allyl alcohol, primary alcohol, secondary alcohols to the corresponding aldehydes or ketones(70%-95%). The selective oxidation of alcohols was also examined by (C9H7NH)2Cr2O7 in [DMF]N,N-dimethylformamide, acetone. (C9H7NH)2Cr2O7 was selective oxidizing agent(75%-95%) of benzyl alcohol, allyl alcohol and primary alcohol in the presence of secondary ones. As a result, (C9H7NH)2Cr2O7 was selective oxidizing agent of benzyl alcohol, allyl alcohol and primary alcohol in the presence of secondary alcohol ones. ln [DMF]N,N-dimethylformamide solvent, (C9H7NH)2Cr2O7 oxidized benzyl alcohol[H] and substituted benzyl alcohols[p-OCH3, m-CH3, m-OCH3, m-Cl, m-NO2], smoothly in the presence of acidic catalyst[H2SO4]. The reaction was dependent on alcohol, (C9H7NH)2Cr2O7 and acid concentration[H2SO4]. Electron donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant[ρ= -0.68, 308K]. The observed experimental data have been rationalized. The hydride ion transfer causes the prior formation of a chromate ester in the rate determining step.