Barriers to rotation adjacent to double bonds. 4. Effect of basis set on structures, and of electron correlation on relative energies
✍ Scribed by Kenneth B. Wiberg; Mark A. Murcko
- Publisher
- John Wiley and Sons
- Year
- 1988
- Tongue
- English
- Weight
- 553 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
The optimized geometries for the rotamers of propanal, 2-butanone, isobutyraldehyde, methyl isopropyl ketone, and isobutyric acid obtained using the 3-21G and 6-31G* basis sets are compared, and systematic changes are noted. The relative 6-31G* energies using the 3-21G and 6-31G* geometries are generally the same within 0.1 kcal/mol. The effect of electron correlation on the relative energies is generally small. These and related data show that 6-31G* relative energies obtained using 3-21G geometries are generally satisfactory when studying rotation about C -C bonds. However, this is not the case for C -0 bonds. The calculated relative energies of isomeric compounds are reproduced only with the full MP4 correction for electron correlation.