Synthesis of Benzaldehyde and Benzoic Acid by Selective Oxidation of Benzyl Alcohol with Iron(III) Tosylate and Hydrogen Peroxide: A Solvent-Controlled Reaction

Abstract

Solvent effect plays a significant role in manipulating the chemical reactivity. As shown herein, selective oxidation of benzyl alcohol (BnOH) by 30 wt% hydrogen peroxide (H2O2) with iron(III) tosylate is a solvent-controlled reaction. The use of different solvents, dissimilar products can be obtained in the reaction: in chloroform, quantitative conversion to benzaldehyde (BnH) is achieved; while high yield is obtained when producing benzoic acid (BA) in acetonitrile. This phenomenon is related not only to the polarity of organic solvents, but also to the interaction energies between BnH and different solvents molecules. Molecular dynamics (MD) calculated by Materials Studio (Accelrys Software Inc., US) show a strong interaction between BnH and chloroform molecules, which means BnH (generated from the oxidation of BnOH) can be effectively protected by chloroform so as to prevent further oxidation to BA. Moreover, a free radical catalytic mechanism is verified in the oxidation of BnOH with H2O2 catalyzed by Fe(OTs)3·6H2O by a poisoning tests using BQ as the radical scavenger.