化学修饰在质谱中的应用 I:长链不饱和脂肪酸的双键定位: 2-烯基取代杂环化合物的质谱

作者提出了一种用"远端基团修饰法"来确定双键位置的新途径.长链不饱和脂肪酸环化为相应的2-烯基杂环化合物后,这些杂环母核的强大的正荷定域作用使产物的质谱的结构专一性大为提高,并能直接提供有关双键位置的信息.本文报道了微量衍生化方法与八类代表性杂环衍生物与四种苯并唑衍生物的质谱比较.

Chemical modification in organic mass spectrometry I: The double bond location of long-chain olefinic acids: the mass spectra of 2-alkenyl-substituted heterocycles

A novel approach to double bond location in long-chain olefinic acids has been elaborated by means of "remote functional group modification". This method consists of converting the carboxylic acid into the corresponding 2-alkenyl-substituted heterocycle followed by measuring its 70 eV mass spectrum. The inherited tendency of random migration of the double bond along the aliphatic chain under electron impact is strongly suppressed by incorporating the terminal carboxyl group into a heterocycle. The derivatives thus prepared show more informative spectra which clearly indicate the site of unsatn. of the parent acids. Submilligram scale derivatization of the olefinic acids, as exemplified by the model compound oleic acid, and a comparison of the spectra of the resulting heterocycles as well as benzoxazole derivatives of selected carboxylic acids are described.