Ultrasound accelerated esterification of palmitic acid with vitamin C

The esterification of palmitic acid with vitamin C in the presence of concentrated sulfuric acid as the solvent and catalyst by means of 25 kHz ultrasonic irradiation to obtain l-ascorbyl 6-palmitate is studied. By using ultrasound the dissolution rate of the reactants can be accelerated greatly, the reaction time of esterification can be reduced from 36 to 2 h, and better yield (90-93%) of ester can be given by using 95% concentrated sulfuric acid as the solvent and catalyst, contrast to the yield of 75-85% by using 99% concentrated sulfuric acid without ultrasound. The influence of reaction conditions and ultrasonic parameters to the yield of ascorbyl palmitate are reported.