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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Can O-H Acid be More Acidic Than Its S-H Analog? A G2 Study of Fluoromethanols and Fluoromethanethiols
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Can O-H Acid be More Acidic Than Its S-H Analog? A G2 Study of Fluoromethanols and Fluoromethanethiols

机译:O-H酸能比S-H类似物酸性更高吗?氟甲醇和氟甲硫醇的G2研究

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摘要

Acidities and homolytic O-H bond dissociation energies of CH_nF_(3-n)OH and CH_nF_(3-n)SH (n = 0-3) were calculated at the G2 level of theory. The variation of the geometry of the neutral species and products of heterolytic and homolytic proton abstraction processes, as well as the energetics (gas-phase acidities and homolytic bond dissociation energies of the title compounds), upon successive fluorine substitution has been studied. The results show that the progressive introduction of fluorine atoms into methanol and methanethiol reduces significantly the acidity gap between the representatives of these two series. Therefore, the calculations indicate that the acidities of CF_3OH and CF_3SH are predicted to be rather close: the former compound is expected to be 0.1 kcal/mol more acidic than its SH counterpart. It was concluded that negative (anionic) hyperconjugation and electrostatic effects are mainly responsible for such behavior.
机译:在理论的G2水平上计算CH_nF_(3-n)OH和CH_nF_(3-n)SH(n = 0-3)的酸度和O-H键的均解能。研究了连续氟取代后中性物质和杂溶质子和均质子质子提取过程的产物的几何形状以及能量(标题化合物的气相酸度和均质键解离能)的变化。结果表明,将氟原子逐步引入甲醇和甲硫醇可显着减小这两个系列代表之间的酸度差距。因此,计算表明,预计CF_3OH和CF_3SH的酸度非常接近:预期前一种化合物的酸度比其SH对应物高0.1 kcal / mol。结论是负(阴离子)过度共轭和静电效应是造成这种行为的主要原因。

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