三聚乙醛氯化合成二氯乙醛

二氯乙醛是合成杀虫剂滴滴滴的中间体,它可由三聚乙醛或乙醛接触氯化而制得。作者对氯化反应的条件,包括触媒选择、反应温度的分段控制等作了详细的研究,并获得较好收率的结果。 试验证明,三聚乙醛或乙醛接触氯化的触媒,以三氯化銻活性为好,硫黄次之。反应温度、触媒用量及反应物料分子比等条件必须严加控制。产品中二氯乙醛含量为90～95％,二氯乙醛的收率可达75～78％。 三聚乙醛或乙醛接触氯化的主要副反应是聚合生成焦油状蒸馏残渣。升高反应温度或增加三氯化銻触媒用量,均促使聚合副反应的增加,以致二氯乙醛收率下降。

SYNTHESIS OF DICHLOROACETALDEHYDE BY CATALYTIC CHLORINATION OF PARALDEHYDE

Dichloroacetaldehyde, an intermediate of organic insecticide, can be synthesized by the catalytic chlorination of paraldehyde or aldehyde. The selection of catalysts, the temperature of various stages of the reaction, etc., were investigated and dichloroaldehyde was obtained in good yields.The experimental results indicate that antimony trichloride is more active than sulfur for catalytic chlorination of paraldehyde or aldehyde. It is necessary to control the reaction temperature, the quantity of catalyst and the molar ratio of the reactants accurately. The product, containing 90~95% of dichloroacet-aldehyde, was obtained in 75~78% yields.Formation of tarry distillation residue due to the polymerization increases with the increasing of the reaction temperature or the quantity of antimony trichloride.