The Microwave Spectrum of m-Tolunitrile: Methyl Internal Rotation and 14N Nuclear Quadrupole Coupling

Internal rotation effects in the pulsed jet rotational spectrum of the trifluoromethane–carbon dioxide dimer

“…(3)) were found to be necessary to obtain a fit to within the measurement uncertainty of the spectrometer (Table 2) [21,24,25].…”

“…(D c3J could not be determined from the available data set; thus, it was fixed to zero in the fit.) The H ird terms in the Hamiltonian are of an empirical nature [24], and since they were developed for fitting the spectra of monomers they may not fully describe the more significant distortion effects likely to be present in a weakly bound dimer with a much more floppy nature. Despite the inclusion of the additional interaction terms, it was necessary to drop seven E state transitions with K a P 2 or DK c = 2 from the fit due to larger (15-80 kHz) residuals for these lines.…”

Structural and Torsional Properties of o-Cresol and o-Cresol-OD as Obtained from Microwave Spectroscopy and ab Initio Calculations

“…Due to the promising results of our recent work (24,25) we calculated the barrier to internal rotation with the Gaussian 94 (26) ab initio package. Second order Møller-Plesset perturbation theory (MP2) was used with the 6-311G * * basis set.…”

The Microwave Spectrum of 1-Chloro-2-methylpropene

“…In a first step, single-point calculation on the MP2/6-311G** level were carried out to compare the ratio between the barrier heights of top 1 and top 2 with our experimental data. For these calculations the distances and angles from Guirgis et al (1) Investigations of Xu et al (8) and also our own attempts to determine a hindering barrier of molecules with low barrier (9,7,10) have shown that accuracy is much improved if a complete ab initio structure optimization is carried out at each rotation angle, keeping only ␣ 1 and ␣ 2 fixed. Therefore, we repeated the calculations in the same grid as before and allowed for structure relaxation.…”

“…In such cases quantum chemistry programs can be valuable. In the past, ab initio calculations were successfully used to determine the hindering barrier of one-top molecules like methanol (8), acetaldehyde (8), and the three tolunitrils (9,7,10). The treatment of the two-top problem 1-chloro-2-methylpropene is straightforward.…”