H. Nguyen, W. Stahl
Dec 1, 2010
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Journal
Journal of Molecular Spectroscopy
Abstract
Abstract The Fourier transform microwave spectrum of isopropenyl acetate (CH 3 COO C(CH 3 ) CH 2 ) has been measured under molecular beam conditions. The experimental data as well as quantum chemical calculations have shown that this molecule exists as only one conformer of C 1 symmetry, in which the vinyl group is tilted by an angle of approximately 70° against the plane containing the ester group. Due to internal rotation of the acetyl methyl group, we found large A – E splittings of all lines (from a few MHz up to 1 GHz or more). We also were able to resolve the splitting due to the internal rotation of the second isopropenyl methyl group. The A species lines split into doublets and the E species lines into triplets. These splittings vary from 10 kHz up to 1 MHz, much smaller than the splittings due to the acetyl methyl group. By analyzing the spectrum with the program Xiam, a torsional barriers of 135.3498(38) and 711.7(73) cm −1 for the acetyl methyl group and the isopropenyl methyl group were observed, respectively. All lines in the spectrum were also fitted with the program Erham to a standard deviation of only 2.3 kHz.