Even-electron ions: a systematic study of the neutral species lost in the dissociation of quasi-molecular ions
Even-electron ions: a systematic study of the neutral species lost in the dissociation of quasi-molecular ions
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DOI：
10.1002/jms.1234
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发表时间：
2007-08-01
影响因子：
2.3
通讯作者：
Ingendoh, Amid
中科院分区：
文献类型：
--
作者：
Levsel, Karsten;Schiebel, Hans-Martin;Ingendoh, Amid
利用离子阱和仪器，研究了电喷雾电离（ESI）或大气压化学电离（APCI）电离的121种模型化合物（主要是具有1至3个官能团的小芳香族化合物）的偶电子[M + H](+)和/或[M - H](-)离子的碰撞诱导解离，并将结果与文献数据进行了比较。虽然某些官能团（例如负离子模式下的 COOH、COOCH3、SO3H，或正离子模式和负离子模式下的 NO2）通常会促进特征性和特异性中性粒子的损失，但其他官能团（例如正离子模式下的 COOH）会引起特征性而非特异性中性粒子的损失。最后，芳香族化合物中的 OH 和 NH2 等官能团不会导致反映这些取代基存在的中性值的损失。一般来说，由脂肪族化合物或含有脂肪族部分的化合物产生的[M + H](+)和[M - H](-)离子的解离遵循偶电子规则（失去分子），但有时在芳香族化合物，特别是硝基芳香族化合物中观察到偏离该规则（失去自由基）。 CBS-QB3 理论水平的热化学数据和从头计算为这些例外情况提供了解释。当比较偶电子[M + H](+)和/或[M - H](-)离子(由ESI或APCI产生)与相应的奇电子[M](+)离子(由电子电离，EI产生)的解离行为时，可以区分三种情况：(1)两种离子的解离完全不同； (2) 解离涉及公共中性点的损失，产生质量相差 1 Da 的子离子，或 (3) 解离导致公共子离子。版权所有 (c) 2007 John Wiley & Sons, Ltd.
The collision-induced dissociations of the even-electron [M + H](+) and/or [M - H](-) ions of 121 model compounds (mainly small aromatic compounds with one to three functional groups) ionized by electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) have been studied using an ion trap, instrument, and the results are compared with the literature data. While some functional groups (such as COOH, COOCH3, SO3H in the negative ion mode, or NO2 in both the positive and negative ion modes) generally promote the loss of neutrals that are characteristic as well as specific, other functional groups (such as COOH in the positive ion mode) give rise to the loss of neutrals that are characteristic, but not specific. Finally, functional groups such as OH and NH2 in aromatic compounds do not lead to the loss of a neutral that reflects the presence of these substituents. In general, the dissociation of [M + H](+) and [M - H](-) ions generated from aliphatic compounds or compounds containing an aliphatic moiety obeys the even-electron rule (loss of a molecule), but deviations from this rule (loss of a radical) are sometimes observed for aromatic compounds, in particular for nitroaromatic compounds. Thermochemical data and ab initio calculations at the CBS-QB3 level of theory provide an explanation for these exceptions. When comparing the dissociation behaviour of the even-electron [M + H](+) and/or [M - H](-) ions (generated by ESI or APCI) with that of the corresponding odd-electron [M](+) ions (generated by electron ionization, EI), three cases may be distinguished: (1) the dissociation of the two ionic species differs completely; (2) the dissociation involves the loss of a common neutral, yielding product ions differing in mass by one Da, or (3) the dissociations lead to a common product ion. Copyright (c) 2007 John Wiley & Sons, Ltd.