Abstract

Abstract The MM3 molecular mechanics program has been extended to conjugated systems. A VESCF method is applied to the pi‐system to calculate bond orders, from which various stretching and torsional parameters are obtained. The procedure gives somewhat better results than the analogous MM2 calculations. It has been applied to a study of 81 compounds of aromatic and other conjugated hydrocarbons, as well as 45 alkenes and unconjugated polyenes. The structures calculated are generally in good agreement with experiment, and the heats of formation of these compounds can be calculated with a rms value of 0.62 kcal/mol, which may be compared with the average experimental error of 0.61 kcal/mol. In addition, vibrational frequencies for five representative conjugated model structures are calculated, with an rms value of 46 cm −1 , and from these, other properties such as entropy can be calculated.

Keywords

Conjugated systemChemistryStandard enthalpy of formationComputational chemistryMolecular mechanicsThermodynamicsPhysical chemistryOrganic chemistryMolecular dynamicsPhysicsPolymer

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Publication Info

Year
1990
Type
article
Volume
11
Issue
7
Pages
868-895
Citations
214
Access
Closed

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Norman L. Allinger, Fanbing Li, Liqun Yan et al. (1990). Molecular mechanics (MM3) calculations on conjugated hydrocarbons. Journal of Computational Chemistry , 11 (7) , 868-895. https://doi.org/10.1002/jcc.540110709

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DOI
10.1002/jcc.540110709