Phase Transfer Catalyzed Synthesis Of Mandelic Acid Process Research

The synthesis of mandelic acid from benzaldehyde and chloroform in the presence of a phase transfer catalyst was studied and the effect of reaction factors, especially the phase transfer catalysts on the yield of the product was discussed. Under favorable conditions, i.e. react at 60癈 for 5 hours in the presence of a 3% of TBAB as catalyst, 78% yield of the product was obtained. It was found that in addition to quaternary ammonium salts, some tertiary amines can also be used as a catalyst for the reaction. A mechanism involving the interaction between the tertiary amine and dichlorocarbene was proposed to explain the catalytic action of the tertiary amine. The asymmetric synthesis of mandelic acid in the presence of a chiral phase transfer catalyst was also studied. Results show that if the reaction is carried out in chloroform no asymmetric synthesis was observed. Addition of an aromatic solvent to the reaction system does lead to the observation of asymmetric synthesis. The effects of aromatic solvents, catalyst amount used and reaction conditions on the enantiomer excess (e. e.) of the reaction were discussed.