A Comparison of the Accuracy of Semi-empirical PM3, PDDG and PM6 methods in Predicting Heats of Formation for Organic Compounds

Yang-Yang Wu, Feng-Qi Zhao, Xue-Hai Ju


Gas phase heats of formation (HOF) of 18 kinds of 390 organic compounds were calculated by quantum chemical calculation using semi-empirical PM3, PDDG and PM6 methods. The calculated HOFs were compared with the experimental data to illustrate the accuracy for different kinds of organics. Furthermore, the calculated values were linearly fitted with experimental values using the least square method, and were afterward substituted into the fitted regression equations to obtain the calibrated ones. The results show that, for 10 kinds of the selected organics, PM6 is more accurate, and PDDG is more accurate for 7 kinds of organics, while PM3 is only good for amino acid. As a whole, PM6 predicts the HOFs more accurately, with its weighted total mean average deviation (WTMAD) being 0.4 kJ/mol and 2.4 kJ/mol smaller than those of PM3 and PDDG, respectively. On the other hand, our results show that PDDG is the best to differentiate the isomers, with its mean average deviation (MAD) for isomerization energy being 7.8 kJ/mol and 11.0 kJ/mol smaller than PM6 and PM3, respectively. After the calibration, the values of MADs from the PM3, PDDG and PM6 results for most organics are reduced by 0.1 to 18.2 kJ/mol, with exceptions of the PM3 for amines, PDDG for carboxylic acids, and PM6 for ethers.


Heat of formation (HOF); semiempirical molecular orbital theory; PM3; PDDG; PM6; linear fitting

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DOI: http://dx.doi.org/10.29356/jmcs.v58i2.182


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Journal of the Mexican Chemical Society (J. Mex. Chem. Soc.) Vol 62, No 2 (2018). Quarterly publication (April-June). Edited and distributed by Sociedad Química de México, A.C. Barranca del Muerto 26, Col. Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico City. Phone: +5255 56626837; +5255 56626823 Contact: soquimex@sqm.org.mx http://www.sqm.org.mx Editor-in-Chief: Ignacio González-Martínez. Indexed Journal. Certificate of reserved rights for recurrent publications under digital distribution granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 04-2018-091118040000-203. Certificate of lawful title and content: Under procedure. ISSN-e granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 2594-0317. ISSN granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 1870-249X. Postal registration of printed matter deposited by editors or agents granted by SEPOMEX: IM09-0312 Copyright © Sociedad Química de México, A.C. Total or partial reproduction is prohibited without written permission of the right holder. The Figures/schemes quality and the general contents of this publication are full responsibility of the authors. Updated December 12th, 2018 by Adriana Vázquez (editorial assistant, e-mail: editor.jmcs@gmail.com), J. Mex. Chem. Soc., Sociedad Química de México, A.C.