THEORETICAL-STUDIES OF THE METHYL ROTATIONAL BARRIER IN TOLUENE

We report computations of the rotational barrier of the methyl group i n toluene. The computations are based on the use of the GAUSSIAN 92 Pr ogram Package with the 6-311G* basis set. The results are 2.69 wavenu mbers at the HF level of approximation and 5.02 wavenumbers at the MP2 level. These results compare favorably with the experimental value of 4.9 wavenumbers. It is shown that inclusion of the vibrational zero-p oint energy in the calculations is necessary for obtaining satisfactor y results.