Catalytic Synthesis of Amino Acid Ester Hydrochloride by Hydrogen Chloride
1. Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China;
2. Hangzhou Xinde Environmental Protection Technology Co Ltd, Jiande 311604, China
Abstract The esterification reaction of amino acids and benzyl alcohol was used as the model to study the amino acid esterification process catalyzed by hydrogen chloride. The water from reaction was removed by azeotropic distillation using 1,2-dichloroethane as solvent, to promote the esterification reaction and the target product amino acid benzyl ester hydrochloride was obtained by recrystallization. When the molar ratio of amino acid to benzyl alcohol was 1.00:1.08, the reaction temperature 83 ℃, the reaction time 4-6 h, the yield was about 65%. In addition, when the amino acid was esterified with a low boiling point alcohol such as methanol, the equilibrium conversion rate of the reaction was improved by using the alcohols as the reactant and water-carrying agent simultaneously. The distilled alcohol was then re-added to the reaction system after the water removal treatment, and the yield of the amino acid ester hydrochloride was of 75% to 85%. The reaction-separation coupling technique improved the yield and purity of the product, shortened the reaction time and reduced the amount of raw materials.
