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氯乙酸甲酯是常用的制药中间体。过去采用氯乙酸和甲醇(99％以上)在浓硫酸作用下进行酯化,收率从80％到87％。反应式: 改进后,采用共沸酯化法。其主要原理为氯乙酸与稀甲醇在1:1:3配比的条件下反应,并共沸蒸馏使酯化物、甲醇和水在一定比例下共同蒸出。这样生成的氯乙酸甲酯不断离开反应系统,反应卽不断正向进行。然后将馏出物分层分离再減压精馏,收率达97％以上,质量完全符合要求。
Methyl chloroacetate is a commonly used pharmaceutical intermediate. In the past with chloroacetic acid and methanol (99%) in the role of concentrated sulfuric acid esterification, the yield was 80% to 87%. Reaction: After the improvement, the use of azeotropic esterification method. The main principle is the reaction of chloroacetic acid and dilute methanol in the ratio of 1: 1: 3, and azeotropic distillation to esterify, methanol and water in a certain proportion of the total steam. The methyl chloroacetate thus formed continuously leaves the reaction system and the reaction proceeds continuously. Then, the distillate was separated and separated and then vacuum distillation was carried out, the yield was over 97%, and the quality completely met the requirement.