Abstract:

3,6-Dichloropicolinic acid(3,6-DCP)as a highly active and low-toxicity compound is mainly used as herbicide, pesticide and plant growth regulator.Synthesis methods of 3,6-DCP are summarized as follows:(1)Due to high cost,hydrolysis of 3,6-dichloro-2-(trichloromethyl)pyridine or 2-cyano-3,6-dichloropyridine to prepare 3,6-DCP(in spite of the method is good in reaction selectivity)is not suitable for commercial production.(2)The synthesis method of 3,6-DCP by hydrolysis-reduction dechlorination of 2-cyano-3,4,5,6-tetrachloropyridine or reduction dechlorination of 3,4,5,6-tetrachloropicolinic acid is replaced by electrochemical methods because hydrazine and cyanide must be used in this method, though the method could provide many advantages, such as low price of raw materials and reaction equipment, high yield(70%—80%).(3)Electrochemical synthesis is gradually becoming the main method to prepare 3,6-DCP in commercial production, and very high yield(>90%)and product purity(95%)can achieved by using this method.In addition, two separation methods of 3,6-DCP are compared: extraction-stripping and neutralization-crystallization-extraction, the former is a more effective method for separation because of its better performance.Based on the statements above, some suggestions for the synthesis of 3,6-DCP are presented.

摘要：

3,6-二氯吡啶甲酸是一种高活性、低毒的农药，主要用作除草剂、杀虫剂和植物生长调节剂。综述了3,6-二氯吡啶甲酸的合成方法并重点介绍了电化学还原脱氯法。水解法反应选择性较高，但原料成本太高，难以实现工业化；肼还原脱氯-水解法和肼还原脱氯法原料制备较为方便，设备比较简单，反应收率可达70%～80%，但反应中需使用剧毒的氰化物和肼，因此该方法逐渐被淘汰；电化学还原脱氯法是目前生产3,6-二氯吡啶甲酸最有效的方法，该方法产品收率可达90%以上，产品纯度95%以上。介绍了3,6-二氯吡啶甲酸的分离方法，化学萃取法与中和结晶-萃取法相比综合性能较优，是相对较适合的方法。在此基础上对3,6-二氯吡啶甲酸合成研究工作的前景作了展望。