Martiskainen Olli, Gawinecki Ryszard, Ośmiałowski Borys, Wiinamäki Kirsti, Pihlaja Kalevi
Structural Chemistry Group, Department of Chemistry, University of Turku, FI-20014 Turku, Finland.
Rapid Commun Mass Spectrom. 2009 Apr;23(7):1075-84. doi: 10.1002/rcm.3972.
Tautomerism has been studied conventionally in solutions or in the solid state. However, the importance of mass spectrometry in the gas phase was realized relatively late. 2-Phenacylquinolines are known to undergo ketimine-enaminone tautomerism. The ratio of tautomers is dependent on the nature of the phenyl ring substituent and the Hammett substituent constants sigma. Theoretical calculations indicate the presence of ketimine and enaminone tautomers in the gas phase. The electron ionization mass spectra of eight 2-phenacylquinolines (ketimine form) were recorded at 70 eV in order to determine the fragmentation routes and to screen for the presence of their enaminone tautomers, (Z)-2-benzoylmethylene-1,2-dihydroquinolines, in the gas phase. The relative abundances or total ion currents of some ions correlated with the Hammett substituent constants and Hammett-Brown constants. The product ions M-CO and M-HCO were observed. A reaction mechanism is suggested for the formation of these ions, requiring skeletal rearrangements. The results furnish information relating to tautomerism in the gas phase.
互变异构通常是在溶液或固态中进行研究的。然而，质谱在气相中的重要性相对较晚才被认识到。已知2-苯甲酰基喹啉会发生酮亚胺-烯胺酮互变异构。互变异构体的比例取决于苯环取代基的性质和哈米特取代基常数σ。理论计算表明气相中存在酮亚胺和烯胺酮互变异构体。记录了八种2-苯甲酰基喹啉（酮亚胺形式）在70 eV下的电子电离质谱，以确定裂解途径并筛选气相中其烯胺酮互变异构体（Z）-2-苯甲酰基亚甲基-1,2-二氢喹啉的存在情况。一些离子的相对丰度或总离子流与哈米特取代基常数和哈米特-布朗常数相关。观察到了产物离子M-CO和M-HCO。针对这些离子的形成提出了一种反应机理，该机理需要骨架重排。这些结果提供了与气相中互变异构有关的信息。
