Theoretical study on the molecular structures of toluene, para-fluorotoluene, para-chlorotoluene, and 4-methylpyridine and their sixfold internal rotational barriers
✍ Scribed by P. C. Chen; F. M. Chang
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 145 KB
- Volume
- 77
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Two kinds of sixfold internal rotational configurations of toluene, para-fluorotoluene, para-chlorotoluene, and 4-methylpyridine were calculated using Hartree-Fock (HF), second-order Møller-Plesset (MP2), and Beck's three parameter hybrid functional using the LYP correlation functional (B3LYP) theory methods with various high-level basis sets. Structures and energies were compared for different configurations. Calculations indicate that the orthogonal configuration has a local minimum while the planar configuration is a transition structure. Furthermore, geometries of the orthogonal and the planar configurations are quite similar, except for a methyl CH bond. Sixfold internal rotational barriers were calculated from the energy difference of two different configurations. For the calculated results, HF methods underestimated the rotational barriers, but MP2 calculations overestimated them. However, the density functional theory (DFT) method is a reliable method since the calculated internal rotational barriers are similar to the experimental ones.