【摘要】 N-甲基-N-(三甲基硅烷)三氟乙酰胺(MSTFA)是一种重要的衍生化试剂,其质谱峰的归属对于深入研究其反应机理具有深刻意义.因此,首次采用密度泛函理论(DFT),在B3LYP/6-311G**水平上对MSTFA及其含氟衍生物质谱裂解反应机理及裂解反应竞争关系进行深入研究.通过对各驻点进行结构优化、振动分析和布局分析,以及成键的过程和能量的计算,验证了实验GC/MS谱图的正确性,确定了最有可能的裂解途径,其结果与谱图分析相一致,是由于α断裂后发生骨架重排反应,形成偶电子离子氟代二甲基硅正离子(m/z 77)和1个中性分子.这不但验证了质谱图分析的正确性,而且也表明了骨架重排在m/z 77产生过程的重要作用.因此,计算化学将会是一种更简便、直接、精确和系统地解析质谱反应机理的有效实施代替方案.更多还原

【Abstract】 N-methyl-N-(trimethylsilane) trifluoroacetamide(MSTFA) is an important derivatization reagent,the attribution of its mass spectrum peak is of great significance for the further study of its reaction mechanism.Therefore, density functional theory(DFT) is used for the first time in this work, at the B3 LYP/6-311 G** level, the mechanism of mass spectrometry cracking reaction of MSTFA and its fluorine-containing derivatives and the competition of cracking reaction were studied. Through the structural optimization, vibration analysis and layout analysis of each stationary point, as well as the calculation of bonding process and energy, the correctness of the experimental GC/MS chromatogram is verified, and the most possible cracking path is determined, and the results are consistent with the spectral analysis. It is due to the skeleton rearrangement reaction after α-cleavage, resulting in the formation of even electron ion fluorinated dimethyl silicon positive ion(m/z 77) and a neutral molecule. This not only verified the correctness of mass spectrogram analysis, but also showed the important role of skeleton rearrangement in the generation of m/z 77. Therefore, computational chemistry will be a more convenient, direct,accurate and systematic alternative to the effective implementation of analytical mass spectrometry reaction mechanism.更多还原