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On the heat of formation of nitromethane

机译：关于硝基甲烷的生成热

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摘要

Two experimental values (-19.3 +/- 0.3 and -17.8 +/- 0.1 kcal/mol) for the gas phase heat of formation (Delta H-f(g)0) (298k) of nitromethane have been reported. Although these values differ try only 1.5 kcal/mol, substantially greater differences in theoretical and experimental results occur when these differing values are used to calculate thermodynamic properties. This is especially evident when these two values for the Delta H-f(g)0 of nitromethane are used to calculate thermodynamic properties of polynitro compounds. For example, when density functional theory (DFT) is coupled with the use of isodesmic reactions, the Delta H-f(g)0 of octanitrocubane is calculated to be 160.6 or 172.6 kcal/mol, depending on which value is used. It should also be appreciated that several computational theories depend upon having access to reliable experimental data for testing and development. We have examined this discrepancy using several computational models and several levels of theory. Our results coupled with a comprehensive review of the literature support the lower (-19.3 +/- 0.3 kcal/mol) experimental value. This is problematic because the higher value (-17.8 +/- 0.1 kcal/mol) has been used in the development and/or testing of several semiempirical quantum mechanical models as well as ab initio Gaussian theory (G2 and G3). Copyright (C) 2008 John Wiley & Sons, Ltd.
机译：已经报道了硝基甲烷的气相生成热（ΔH-f（g）0）（298k）的两个实验值（-19.3 +/- 0.3和-17.8 +/- 0.1 kcal / mol）。尽管这些值仅尝试了1.5 kcal / mol，但当使用这些不同的值来计算热力学性质时，理论和实验结果会出现更大的差异。当使用这两个硝基甲烷Delta H-f（g）0值来计算多硝基化合物的热力学性质时，这一点尤其明显。例如，当密度泛函理论（DFT）与等渗反应结合使用时，根据所使用的值，八硝基古巴的Delta H-f（g）0计算为160.6或172.6 kcal / mol。还应当理解，几种计算理论取决于对可靠的实验数据的访问以进行测试和开发。我们已经使用几种计算模型和几种理论水平检查了这种差异。我们的结果加上对文献的全面回顾，支持了较低的（-19.3 +/- 0.3 kcal / mol）实验值。这是有问题的，因为较高的值（-17.8 +/- 0.1 kcal / mol）已用于开发和/或测试几个半经验量子力学模型以及从头算高斯理论（G2和G3）。版权所有（C）2008 John Wiley＆Sons，Ltd.

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