手性化合物在质谱中光学稳定性的研究

反应质谱法自创立以来 ,已广泛应用于有机立体化学的研究领域 .其方法是在质谱离子源中引入反应试剂 ,使之与分析物发生立体选择性反应产生特征离子 ,通过这些特征离子可获得待分析样品的立体化学信息 1] .我们 2～ 5 ] 在前期工作中 ,通过在质谱中引入手性反应试剂造成手性环境 ,成功地研究了对映体的绝对构型 .由于质谱过程中常伴随着高温、质子酸催化等因素 ,因而随着反应质谱在对映体构型方面研究的深入进行 ,手性反应试剂及手性样品在质谱过程中是否会发生变旋这一问题日益引起我们的重视 .当对映异构体手性中心连接一个氢原子和一个…

Studies on the Optical Stability of Chiral Compounds in EI Mass Spectrometry Process

The optical stability of chiral 2-hydroxy-2-phenylacetic acid in electron ionization mass spectrometry(EIMS) process has been detected directly by deuterium labelling technique. From the EI mass spectrum of deuterated 2-hydroxy-2-phenylacetic acid, the major characteristic fragment ion at m/z 108(the capture of the carbonyl group) and the corresponding isotopic ion(13C) at m/z 109 can be observed, and the ratio of m/z=109 to m/z=108 is about 8%(the calculated value is 7.8%). As enolization of deuterated 2-hydroxy-2-phenylacetic acid in mass spectrometry can yield the characteristic fragment ion at m/z 109 and results in much higher ratio of 109/108 than 8%; this study shows that no enolization takes place during the EI-MS process of 2-hydroxy-2-phenylacetic acid. This results can be concluded that these compounds are optically stable in the process of instantaneous vaporization at high temperature and electron impact ionization.