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首页> 外文期刊>International Journal of Mass Spectrometry and Ion Processes >Mixed-site vs. charge-site-remote fragmentation reactions of long-chain quaternary ammonium ions
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Mixed-site vs. charge-site-remote fragmentation reactions of long-chain quaternary ammonium ions

机译：长链季铵离子的混合位点与电荷位点-远程断裂反应

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摘要

The mixed-site fragmentation reactions discovered by Tuinman, Cook and Magid (J. Am. Soc. Mass Spectrom., 1 (1989) 85), as reaction channels competitive with charge-site-remote fragmentations, have been further investigated. Two complementary deuterium-labelled tetra-alkylammonium ions, (CH3)3N+C14D29 and (CD3)3N+C14H29, were investigated as precursor ions for MS/MS/MS experiments using a sector/time-of-flight hybrid instrument employing orthogonal acceleration into the time-of-flight analyzer. By comparing the second-generation fragment ion spectra originating from the two precursors, it was possible unambiguously to assign atomic compositions and also to make plausible structural assignments. The fragment spectra thus obtained for the first-generation product ions of the charge-site-remote reactions are consistent with previous conclusions concerning their structures. The first-generation product ions from the mixed-site fragmentations, for example (CH3)2N+(CD2)m, are competitive with their charge-site-remote counterparts for m = 4, 5 and 6 in a manner consistent with the anticipated stabilities of cyclic transition states. However, interpretation of the second-generation fragment spectra of the (CH3)2N+(CD2)m ions and their deuterium-labelled complements was best accomplished in terms of a postulated diradical ion intermediate.
机译：由Tuinman，Cook和Magid发现的混合位点裂解反应（J.Am.Soc.Mass Spectrom。，1（1989）85）作为与电荷位点-远端裂解竞争的反应通道，已经被进一步研究。使用正交加速的扇形/飞行时间混合仪器，研究了两个互补的氘标记的四烷基铵离子（CH3）3N + C14D29和（CD3）3N + C14H29作为MS / MS / MS实验的前驱离子。进入飞行时间分析仪。通过比较源自两种前体的第二代碎片离子光谱，可以明确分配原子组成并进行合理的结构分配。如此获得的电荷位点-远程反应的第一代产物离子的碎片光谱与关于其结构的先前结论是一致的。来自混合位点碎片的第一代产物离子，例如（CH3）2N +（CD2）m，与它们的电荷位点远程对应物在m = 4、5和6方面具有竞争性，且与预期的稳定性相一致循环过渡状态。但是，根据假定的双自由基离子中间体，最好能完成对（CH3）2N +（CD2）m离子及其氘标记的补体的第二代碎片光谱的解释。

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