Ultrasonically-promoted synthesis of mandelic acid by phase transfer catalysis in an ionic liquid.

An efficient and facile process to synthesize mandelic acid through phase transfer catalysis (PTC; also phase transfer catalyst) using ultrasound in an ionic liquid has been developed. Mandelic acid was synthesized from benzaldehyde with chloroform in an 89.6% yield at 60°C for 2h by using tetrabutyl ammonium bromide (TBAB) as a phase transfer catalyst. Effects of different factors, such as frequency of ultrasound, reaction temperature, kinds of PTC and solvents had been investigated to obtain the optimum condition. It was observed that the ultrasonically promoted synthesis of mandelic acid by PTC in the ionic liquid exhibited significant enhancement in reaction yields under ambient conditions.

An efficient and practical synthesis of mandelic acid by combination of complex phase transfer catalyst and ultrasonic irradiation.

Mandelic acid was synthesized from benzaldehyde with chloroform in a 81% yield at 60 degrees C for 2 h by using triethylbenzylammonium chloride (TEBA) and poly(ethylene glycol)-800 (PEG-800) as a complex phase transfer catalyst under ultrasonic irradiation. The main advantages of this present method are that the reaction time is much shorter and the yield is higher than those of the classical method. p-Methoxymandelic acid was also obtained in a 84% yield under the same reaction conditions.