用TOF-MS和GC-TOF-MS分析改良乌尔门反应的副产物

采用EI和CI电离方式下的混合样品直接进样法、EI电离条件下的气质联用技术 ,利用飞行时间质谱的精确质量及准确的元素组成 ,鉴定了改良乌尔门反应的副产物多联苯混合物的结构 ,并测定了它的相对含量分别为联苯 1 ( 70 .0 % )、三联苯异构体 2 ( 3.9% )、四联苯异构体 3( 4 .9% )和五联苯及其异构体 5 亚甲基 1 ,2 ,3,4 四苯基 1 ,3 环戊二烯 4 ( 2 1 .2 % ) .由于具有共轭大π键的多联苯分子离子结构相当稳定 ,其纯化合物的分子离子的丰度都接近 1 0 0 %或为基峰 ,可根据混合物直接进样所得质谱 (CI)中各组分分子离子的相对丰度 ,估计出组分 2、3和 4在混合物中的相对含量 .这一结论与气质联用 (EI)所测的总离子流色谱图中 2和 3的相对含量相一致 .对通过重结晶得到的主要副产物纯品联苯 1的EI TOF MS谱作了具体的裂解分析

Analysis of By-Products From Improved Ullmann Reaction Using TOF-MS and GC-TOF-MS

By using direct introduction of mixture samples in both EI and CI mode and technique of GC-MS in EI mode, and utilizing exact mass and accurate elemental composition from TOF mass spectrometry, the structures and relative contents of multiphenyl mixture by-products from the improved Ullmann reaction were determined as follows: 70.0%of diphenyl 1, 3.9% of terphenyl isomers 2, 4.9% of tetraphenyl isomers 3, and 21.2%of pentaphnyl isomers 4. In view of the structures of multiphenyl molecular ion being considerably stable due to the conjugated great π bonds, the molecular ion abundance of any pure mutiphenyl would be nearly 100% (base peak). As a result, it is possible to estimate the relative contents of compounds 2, 3 and 4 in the mixture according to their relative abundances from CI-TOF-MS of the mixture by direct introduction. This conclusion was in good agreement with the data of 2 and 3 from TIC of GC-TOF-MS in EI mode of the mixture. A concrete fragmentation analysis of EI-TOF-MS of the main by-product, the pure diphenyl 1, was conducted.