A general, most basic rule for ion dissociation: Protonated molecules

IF 1.9 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS
Adriano Reis, Rodinei Augusti, Marcos N. Eberlin
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引用次数: 0

Abstract

Contrary to the common but potentially misleading belief that when a protonated molecule is excited, it is its most stable protomer that will mandatorily dissociate, we demonstrate herein that, when rationalizing or predicting the chemistry of such ions, we should always search for the most labile protomer. This “most labile protomer” rule, based on the mobile proton model, states therefore that when a protonated molecule is heated, during ionization or by collisions for instance, the loosely bonded proton (H+) can acquire enough energy to detach itself from the most basic site of the molecule and then freely “walk through” the molecular framework to eventually find, if available, another protonation site, forming other less stable but more labile protomers, that is, protomers that may display lower dissociation thresholds. To demonstrate the validity of the “most labile protomer” rule as well as the misleading nature of the “most stable protomer” rule, we have selected several illustrative molecules and have collected their ESI(+)-MS/MS. To compare energies of precursors and products, we have also performed PM7 calculations and elaborated potential energy surface diagrams for their possible protomers and dissociation thresholds. We have also applied the “most labile protomer” rule to reinterpret—exclusively via classical charge-induced dissociation cleavages—several dissociation processes proposed for protonated molecules. In an accompanying letter, we have also applied a similar “most labile electromer” rule to ionized molecules.

离子解离的一般最基本规则:质子化分子。
人们普遍认为,质子化分子受到激发后,其最稳定的原生质体必须解离,但这一观点可能会误导我们,与此相反,我们在本文中证明,在合理解释或预测此类离子的化学性质时,我们应始终寻找最易失效的原生质体。因此,这条基于移动质子模型的 "最易解离原质体 "规则指出,当质子化分子在电离或碰撞等过程中被加热时,松散结合的质子(H+ )可以获得足够的能量,使其脱离分子的最基本位点,然后自由地 "穿越 "分子框架,最终找到(如果有的话)另一个质子化位点,形成其他不太稳定但更易解离的原质体,即可能显示较低解离阈值的原质体。为了证明 "最易变原生体 "规则的有效性以及 "最稳定原生体 "规则的误导性,我们选择了几个示例分子,并收集了它们的 ESI(+)-MS/MS 数据。为了比较前体和产物的能量,我们还进行了 PM7 计算,并详细绘制了它们可能的原生体和解离阈值的势能面图。我们还应用了 "最易变原体 "规则来重新解释--完全通过经典的电荷诱导解离裂解--质子化分子的几种解离过程。在附信中,我们还对电离分子应用了类似的 "最易电离体 "规则。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Mass Spectrometry
Journal of Mass Spectrometry 化学-光谱学
CiteScore
5.10
自引率
0.00%
发文量
84
审稿时长
1.5 months
期刊介绍: The Journal of Mass Spectrometry publishes papers on a broad range of topics of interest to scientists working in both fundamental and applied areas involving the study of gaseous ions. The aim of JMS is to serve the scientific community with information provided and arranged to help senior investigators to better stay abreast of new discoveries and studies in their own field, to make them aware of events and developments in associated fields, and to provide students and newcomers the basic tools with which to learn fundamental and applied aspects of mass spectrometry.
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