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氰乙酸(2)是合成磺胺二甲氧嘧啶、茶碱、可可碱的原料化合物。由氰乙酸钠(1)制备2时所使用的硫酸量是影响氰乙酸收率的主要因素。在合成氰乙酰脲3时,2可不分离而直接应用。腈在酸性介质中被水解,所以中和后反应物中过量的硫酸是不需要的。另一方面,酸量不足导致1的分离不完全和降低3的收率。在1过剩0.2～0.4 g/100 ml时,3达到最高收率(93～95%)。这时1/硫酸的摩尔比为1∶0.541～0.564。在温度28～30℃和搅拌下向174.4 g的
Cyanoacetic acid (2) is the synthesis of sulfamethazine, theophylline, theobromine base compound. The amount of sulfuric acid used to prepare 2 from sodium cyanoacetate (1) is a major factor affecting the yield of cyanoacetic acid. In the synthesis of cyanoacetyl urea 3, 2 can be used directly without separation. The nitrile is hydrolyzed in an acidic medium so that an excess of sulfuric acid in the reaction after neutralization is not required. On the other hand, insufficient acid results in incomplete separation of 1 and a decrease in yield of 3. At an excess of 0.2-0.4 g / 100 ml, 3 achieved the highest yield (93-95%). In this case, the molar ratio of 1 / sulfuric acid is 1: 0.541 to 0.564. 174.4 g at a temperature of 28-30 ° C with stirring