葡萄糖对天冬酰胺裂解生成氢氰酸的影响机理

Influence Mechanism of Glucose on Formation of Hydrogen Cyanide from Asparagine Pyrolysis

为研究葡萄糖对天冬酰胺裂解生成氢氰酸的影响,采用TG-FTIR技术对天冬酰胺及与葡萄糖混合物裂解生成的HCN,NH3和HNCO进行了分析,采用Py-GC/MS技术对其他挥发性裂解产物进行了鉴定,并通过裂解同位素标记样品和计算主要含氮裂解产物中的同位素比例,推测了其形成途径。结果表明:①当天冬酰胺与相同质量的葡萄糖混合裂解时,HCN的生成量增加,NH3和HNCO的生成量降低。②在葡萄糖参与下,天冬酰胺主要裂解产物的生成量发生变化。相对含量最高的马来酰亚胺的生成量显著下降,而琥珀酰亚胺的生成量增加,腈类、酸类和酰胺类物质生成量也有所增加。除此之外,还产生了大量新的含氮杂环化合物。③在葡萄糖参与下,腈类和酰胺类物质的同位素所占比例较天冬酰胺明显增加,HCN中同位素比例由27%增加至38%。大多数含氮杂环化合物中N原子主要来源于未标记的氨基N,天冬酰胺的氨基更易与葡萄糖的羰基发生缩合反应生成含氮杂环化合物,而酰胺基上的N主要参与形成酰胺类和腈类化合物,从而抑制了天冬酰胺发生分子内脱水环化,C—C键的断裂加剧,进而导致HCN的生成量增加。

In order to investigate the influence of glucose on the formation of hydrogen cyanide （HCN） from asparagine pyrolysis, the pyrolysis products formed from the pyrolysis of asparagine and its mixture with glucose, including HCN, NH3 and HNCO, were analyzed real-timely by TG-FTIR, and the other volatile products were determined with Py-GC/MS. In addition, by the pyrolysis of 18N-labeled asparagine sample and the percentage of isotope in the major nitrogen-containing pyrolysis products, their formation pathways were deliberated. The results indicated that： 1） When the mixture of asparagine and glucose （1：1 by weight） was pyrolysed, the yield of HCN increased, while the yields of NH3 and HNCO decreased comparing with the pyrolysis products of asparagine. 2） The yields of the major pyrolysis products of asparagine changed in the presence of glucose. The yield of maleimide, the predominant pyrolysis product of asparagine decreased significantly, the yields of succinimide increased, nitriles, acids and amides increased slightly. In addition, a large number of N-heterocyclic compounds emerged. 3） With the participation of glucose, the proportion of 15N in nitrile and amide compounds increased obviously, and that in HCN increased from 27% to 38%. The nitrogen of most N-heterocyclic compounds mainly originated from unlabeled amino group, which indicated that the amino group of asparagine might be more likely to react with the carbonyl group of glucose to form N-heterocyclic compounds, while the amide nitrogen mainly involved in the formation of amides and nitriles. Consequently, the intra-molecular dehydration and cyclization reactions were restrained and the C--C rupture of asparagine intensified, which led to the increase of HCN yield.