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On the heat of formation of nitromethane
Author(s) -
Bumpus John A.,
Willoughby Patrick H.
Publication year - 2008
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1358
Subject(s) - nitromethane , chemistry , isodesmic reaction , thermodynamics , standard enthalpy of formation , density functional theory , ab initio , gas phase , computational chemistry , organic chemistry , physics
Two experimental values (−19.3 ± 0.3 and −17.8 ± 0.1 kcal/mol) for the gas phase heat of formation (δ f H 0 g ) (298k) of nitromethane have been reported. Although these values differ by 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 δ f H 0 gof 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 Δ f H 0 gof 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 © 2008 John Wiley & Sons, Ltd.