On the applicability of the MINDO/3 method in studies of molecular structures in the vapor phase. Geometries, conformational energies, and vibrational amplitudes of alkenes and chloroalkanes

✍ Scribed by D. Van Hemelrijk; W. Versichel; C. Van Alsenoy; H. J. Geise

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 584 KB
• Volume: 2
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540020112

✦ Synopsis

Abstract

The geometries and force fields of the different conformers of five alkenes and five chloroalkanes (17 conformers in total) were calculated in the MINDO/3 approximation and compared with the corresponding experimental values. The direct use of geometrical or vibrational parameters derived from MINDO/3 either as starting values or as a source of constraints in the analysis of gas‐phase electron diffraction data presents great risks. After a scaling procedure in which the calculated values are fitted to the experimental ones for a small number of compounds, scale factors can be obtained which, with due caution, are transferable to other molecules in the same class. Scaled MINDO/3 produces geometries and force fields that fit to experiment considerably better than their unscaled counterparts. However, scaled MINDO/3 does not produce better results than molecular mechanics. Calculated energy differences between rotamers are generally too high.