What a difference a chlorine makes: The remarkable unimolecular ion chemistry of phenyl formate and phenyl chloroformate

IF 1.9 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS
Bethany Lowe, Alejandro L. Cardona, Juana Salas, Andras Bodi, Paul M. Mayer, Maxi A. Burgos Paci
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Abstract

Imaging photoelectron photoion coincidence (iPEPICO) spectroscopy and tandem mass spectrometry were employed to explore the ionisation and dissociative ionisation of phenyl formate (PF) and phenyl chloroformate (PCF). The threshold photoelectron spectra of both compounds are featureless and lack a definitive origin transition, owing to the internal rotation of the formate functional group relative to the benzene ring, active upon ionisation. CBS-QB3 calculations yield ionisation energies of 8.88 and 9.03 eV for PF and PCF, respectively. Ionised PF dissociates by the loss of CO via a transition state composed of a phenoxy cation and HCO moieties. The dissociation of PCF ions involves the competing losses of CO (m/z 128/130), Cl (m/z 121) and CO2 (m/z 112/114), with Cl loss also shown to occur from the second excited state in a non-statistical process. The primary CO- and Cl-loss fragment ions undergo sequential reactions leading to fragment ions at m/z 98 and 77. The mass-analysed ion kinetic energy (MIKE) spectrum of PCF+ showed that the loss of CO2 occurs with a large reverse energy barrier, which is consistent with the computationally derived minimum energy reaction pathway.

一氯之差:甲酸苯酯和氯甲酸苯酯的非凡单分子离子化学。
研究人员利用成像光电子光子重合(iPEPICO)光谱和串联质谱法来探讨甲酸苯酯(PF)和氯甲酸苯酯(PCF)的电离和离解电离。由于甲酸酯官能团相对于苯环的内旋转在电离时很活跃,这两种化合物的阈值光电子能谱都没有特征,也缺乏明确的起源转变。CBS-QB3 计算得出 PF 和 PCF 的电离能分别为 8.88 和 9.03 eV。电离后的 PF 通过由苯氧阳离子和 HCO 分子组成的过渡态失去 CO 而解离。PCF 离子的解离涉及 CO(m/z 128/130)、Cl(m/z 121)和 CO2(m/z 112/114)的竞争损耗,Cl 的损耗也在非统计过程中从第二激发态发生。主要的 CO 和 Cl 丢失碎片离子会发生顺序反应,产生 m/z 98 和 77 的碎片离子。PCF+ 的质量分析离子动能(MIKE)谱显示,二氧化碳的损失发生在一个较大的反向能量势垒中,这与计算得出的最小能量反应途径是一致的。
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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