论文部分内容阅读
研究了应用氰化物为接触剂,使三氯乙醛(可能是其加成物,三氯乙醛缩甲醇)与无水碳酸钠在甲醇中的混悬液作用脱氯化氢,一步生成二氯乙酸甲酯。反应温度60—64℃;三氯乙醛滴加速度必须尽可能地快,使整个反应在半小时内结束;加水分出油层;洗滌,干燥,分馏。收率能达到70％以上。但当反应液中氰化物浓度减低时,三氯乙醛水解分裂生成氯仿的趋势即逐渐增加。由于,当先将三氯乙醛与部分甲醇制成三氯乙醛缩甲醇,然后再加到无水碳酸钠和含有氰化钾的甲醇中反应时,结果也同样地好;同时由于,这个反应速度很快,而在反应所用条件下三氯乙醛缩甲醇分解释出游离三氯乙醛的可能性极小;我们提出了反应机制的新解释。
The application of cyanide as a contact agent to make the chloral hydrate dehydrochlorination of trichloroacetaldehyde (possibly its adduct, trichloroacetal carbonated methanol) with anhydrous sodium carbonate in methanol to produce dichloroacetic acid Methyl ester. The reaction temperature is 60-64 ℃; the dropping speed of trichloroacetaldehyde must be as fast as possible so that the whole reaction is completed within half an hour; add water to the oil layer; and wash, dry and fractionate. Yield can reach more than 70%. However, when the concentration of cyanide in the reaction mixture is reduced, the tendency of chloral hydrate to split and form chloroform is gradually increased. Because, when the first chloral and part of the methanol made of trichloroacetalized methanol, and then added to anhydrous sodium carbonate and potassium cyanide containing methanol reaction, the results are equally good; at the same time as this reaction Very fast, and the possibility of the decomposition of trichloroacetalmethanol to liberate free chloral is minimal under the conditions used for the reaction; we present a new explanation of the reaction mechanism.