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本文通过低分辨、高分辨质谱及亚稳离子测定,对α-酮醛的 Schiff 碱类化合物的质谱断裂过程进行了研究.结果表明,这类化合物均不太稳定,分子离子峰的相对强度很小.分子的电子轰击质谱裂解有以下三种基本方式:(1)电离发生在碳氢不饱和双键的 N 原子上,得到 m/z186的离子及其子离子 m/z170,144,143;(2)电离发生在乙酰胺基的 N 原子上,经甲基上的 H 重排,丢失 COCH_2,得到 m/z[M-COCH_2]~+的离子及其骨架重排子离子;(3)电离发生在乙酰基的氧原子上,α断键产生 m/z43的离子.取代基 R 的性质决定了断裂所采取的主要方式.α-酮醛的 Schiff 碱类化合物与喹噁啉环类化合物是同一原料和合成路线在不同溶剂中反应的不同产物,而在质谱离子源中,Schiff碱也存在转变为喹噁啉环的趋势.
In this paper, the mass spectroscopic rupture process of α-ketoaldehyde Schiff bases was studied by low resolution, high resolution mass spectrometry and metastable ion measurements.The results show that these compounds are not stable and the relative intensities of molecular ion peaks are very high Small molecular electron impact mass spectrometry cleavage has the following three basic ways: (1) ionization occurs in the N atom of a hydrocarbon unsaturated double bond, to obtain m / z186 ion and its daughter ions m / z170,144,143; (2 ) Ionization occurs at the acetamido N atom, rearranges by H on the methyl group, and COCH_2 is lost, resulting in ions of m / z [M-COCH_2] ~ + and their framework rearrangement ions; (3) Ionization occurs At the oxygen atom of acetyl, the alpha bond breaks off ions of m / z 43. The nature of the substituent R determines the main mode taken for cleavage.The Schiff base compounds of the alpha-ketoaldehydes are identical to the quinoxaline ring compounds The starting materials and synthetic products react differently in different solvents, and there is a tendency for the Schiff base to convert to a quinoxaline ring in a mass spectrometer ion source.