Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy |
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Authors: | Atef Jabri Vinh Van Dr. Ha Vinh Lam Nguyen Prof.Dr. Wolfgang Stahl Dr. Isabelle Kleiner |
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Affiliation: | 1. Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université Paris Diderot, Créteil cedex, France;2. Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany |
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Abstract: | The Fourier transform microwave spectra of the E and Z isomers of butadienyl acetate were measured in the frequency range from 2 to 26.5 GHz under molecular‐jet conditions. The most stable conformer of each isomer, in which all heavy atoms are located in a symmetry plane, was identified after analyzing the spectrum by comparison with the results from quantum‐chemical calculations. The barriers to internal rotation of the acetyl methyl group were found to be 149.1822(20) and 150.2128(48) cm?1 for the E and Z isomers, respectively, which are similar to that of vinyl acetate. A comparison between two theoretical approaches treating internal rotation, the rho axis method and combined axis method, was also performed. The influence of the alkyl R chain on the methyl torsional barriers in CH3 ‐COOR acetates was explored. |
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Keywords: | ab initio calculations conformational analysis conjugation internal rotation rotational spectroscopy |
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