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E-Journal of Chemistry
Volume 1 (2004), Issue 2, Pages 81-86
http://dx.doi.org/10.1155/2004/728352

The Gas-Phase Heats of Formation of n-Alkanes as a Function of the Electrostatic Potential Extrema on their Molecular Surfaces

Fakhr M. Abu-Awwad

Department of Chemistry, The Islamic University of Gaza, Gaza, Palestinian Authority

Received 2 March 2004; Accepted 17 March 2004

Copyright © 2004 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The hybrid density functional B3LYP is employed to map the molecular electrostatic potentials on the surfaces of twenty normal alkanes, (Cn H2n+2), n = 1-20. It is shown that gas-phase heats of formation of the alkanes can be represented quantitatively in terms of the potential, where a general equation of the heat of formation is introduced as a function of potentials' extrema, VS,min and VS,max with average absolute error of 0.028 kcal/mol and a standard deviation of 0.048 kcal/mol. This should be viewed as a success of the B3LYP functional and the molecular surface electrostatic potential as tools of chemistry. The predicted gas-phase heats of formation of thirty normal alkanes (n = 21-50) are reproduced and compared to their experimental counterparts when available.