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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Long Bonds and Short Barriers: Ionization and Isomerization of Alkyl Nitriles
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Long Bonds and Short Barriers: Ionization and Isomerization of Alkyl Nitriles

机译：长键和短壁垒：烷基腈的电离和异构化

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摘要

Ab initio molecular orbital calculations demonstrate that ionizing alkyl nitriles produces a dramatic geometry change involving lengthening of a C-CH_2CN bond. The experimental determination of the adiabatic ionization energy of these species is thus very difficult. In addition, there are generally low barriers for 1,2-H shift reactions in the molecular ions leading to RCHCHN~(+·) and RCHCNH~(+·) isomers, which makes generating pure ionized alkyl nitrile in a mass spectrometer a challenge. Threshold photoelectron spectroscopy and threshold photoelecton photoion coincidence spectroscopy were employed to study the ionization and dissociation of two alkyl nitriles, in particular, pentanenitrile and 2,2-dimethylpropanenitrile. Threshold ionization is shown to result not in the respective molecular ions, but rather in isomeric forms, resulting in dissociation thresholds that lie below the calculated adiabatic ionization energies of the two molecules. Appearance energies for all observed fragment ions are reported and compared to available literature values. Charge separation in the dissociation of doubly ionized 2,2-dimethylpropanenitrile is observed as fragmention time-of-flight peak broadening at high photon energies.
机译：从头算分子轨道计算表明，电离的烷基腈会产生引人注目的几何变化，其中包括C-CH_2CN键的延长。因此，很难确定这些物质的绝热电离能的实验值。此外，导致RCHCHN〜（+）和RCHCNH〜（+·）异构体的分子离子中1,2-H移位反应的阻隔通常很低，这使得在质谱仪中生成纯离子化烷基腈成为一个挑战。 。阈值光电子能谱和阈值光电子偶合离子能谱被用来研究两个烷基腈，特别是戊腈和2，2-二甲基丙腈的电离和离解。显示阈值电离不是导致各自的分子离子，而是异构体形式，导致离解阈值低于两个分子的计算绝热电离能。报告所有观察到的碎片离子的外观能，并将其与可用的文献值进行比较。在高光子能量下，随着飞行时间峰的加宽，观察到双电离的2，2-二甲基丙腈离解中的电荷分离。

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