KINETIC STUDY OF BENZYL ALCOHOL OXIDATION UNDER PHASE TRANSFER CATALYSIS CONDITIONS

Abstract

In this work, benzyl alcohol oxidation to benzaldehyde by sodium hypochlorite (NaOCl) in the presence of quaternary ammonium salt was successfully carried out in an organic solvent/aqueous solution two-phase medium. An aqueous solution of low pH value is found to be favorable for the oxidation of benzyl alcohol by sodium hypochlorite. However, certain amounts of hypochlorite ions are converted to chlorines in a solution of low pH value simply by adding sulfuric acid. It is thus our goal to find a method for the production of benzaldehyde of high yield in a solution at low pH value and the prevention of chlorine production from sodium hypochlorite. Therefore, the primary purpose of this work is to search for a favorable condition for the production of benzaldehyde. It is effective to adjust the pH value by adding KCl/HCl solution rather than by adding sulfuric acid solution. Under this circumstance, the reaction follows a zero^th order rate law. Kinetics of the oxidation by sodium hypochlorite under phase transfer catalysis condition, including the effect of the agitation speed, the amount of TBAB catalyst, quaternary ammonium salts, the amount of sodium hypochlorite, the amount of sodium hydrogen carbonate, organic solvents, the pH value, the amount of dichloromethane, and the temperature on the conversion were investigated in detail. Reasonable explanations were made to satisfactorily account for the results.

Keywords:

• Benzyl alcohol
• Oxidation
• Quaternary ammonium salts
• Sodium hypochlorite

Acknowledgment

The authors would like to thank the financial support from the National Science Council under the grant NSC 91-E-2214-006.