title: Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy.
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.
authors.affiliation: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université Paris Diderot, 61 avenue du Général de Gaulle, 94010, Créteil cedex, France.
authors.forename: Atef
authors.initials: A
authors.lastname: Jabri
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany.
authors.forename: Vinh
authors.initials: V
authors.lastname: Van
authors.affiliation: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université Paris Diderot, 61 avenue du Général de Gaulle, 94010, Créteil cedex, France. lam.nguyen@lisa.u-pec.fr.
authors.forename: Ha Vinh Lam
authors.initials: HV
authors.lastname: Nguyen
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Stahl
authors.affiliation: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université Paris Diderot, 61 avenue du Général de Gaulle, 94010, Créteil cedex, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kleiner
keywords: ab initio calculations; conformational analysis; conjugation; internal rotation; rotational spectroscopy