一种用于咖啡因检测的新型类木质素序列转氨酶反应

F. Sánchez-Viesca, Reina Gómez
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摘要

这篇通讯是关于哈马斯滕咖啡因测试的理论有机化学研究。他使用了氯水和氢氧化铵;呈紫色表示存在咖啡因。由于形成了紫酸铵的衍生物,该试验一直被认为是一种脲氧化物试验。不过,还有几种重要的变体。尿酸的原始金霉素检测法采用的是稀硝酸;尿酸分子中的五元环是咪唑环,而咖啡因分子中的五元环是咪唑环。这一差异改变了反应的起始位置。尿酸没有取代基,而咖啡因含有三个甲基。甲基 N-7 是紫苏酸形成的一个障碍,因为需要一个伯胺才能与羰基反应并形成双键。因此,由于形成了紫酸铵,所以需要辅助氨解。N-7 位的甲胺与阿脲中活性极高的中心羰基发生反应,从而解释了这种化学性质。这是一种协同机制:氨取代了半氨基的氮,形成了氮碳双键,同时分离出羟基离子。阿脲上的甲基亚氨基被水合,氨基乙醇质子化后恢复阿脲分子并分离出甲基胺。
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A novel transamination reaction in a murexide-like sequence for caffeine detection
This communication is a theoretical organic chemistry study on the Hammarsten test for caffeine. He used chlorine water and ammonium hydroxide; a violet colour indicates presence of caffeine. Since a derivative of ammonium purpurate is formed, the assay has been considered a murexide test. However, there are several important variants. The original murexide test for uric acid employs diluted nitric acid; the five-member ring in uric acid molecule is an imidazolone whereas in caffeine it is an imidazole. This difference alters the reaction starting site. Uric acid has no substituents, caffeine presents three methyl groups. The methyl al N-7 is an impediment for purpuric acid formation since a primary amine is required in order to react with a carbonyl group and form a double bond. So, assisted ammonolysis is invoked since ammonium purpurate is formed. This chemical deportment is explained by reaction of the methylamine at N-7 with the very reactive central carbonyl group in alloxan. A concerted mechanism takes place: ammonia displaces the nitrogen of the hemiaminal, a nitrogen-carbon double bond is formed with concomitant separation of hydroxyl ion. The methylimino group at alloxan is hydrated and protonation of the carbinolamine restores alloxan molecule and separation of methylamine.
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