title: Methyl internal rotation in the microwave spectrum of vinyl acetate.
abstract: The rotational spectrum of vinyl acetate, CH3(CO)OCH═CH2, was measured using two molecular beam Fourier transform microwave spectrometers operating in the frequency range from 2 to 40 GHz. Large splittings up to 2 GHz occurred due to the internal rotation of the acetyl methyl group CH3CO with a V3 potential of 151.492(34) cm(-1), much larger than the barrier of approximately 100 cm(-1) often found in acetates. The torsional transitions were fitted using three different programs XIAM, ERHAM, and BELGI-Cs, whereby the rotational constants, centrifugal distortion constants, and the internal rotation parameters could be determined with very high accuracy. The experimental results were supported by quantum chemical calculations. For a conformational analysis, potential energy surfaces were calculated.
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, D-52074 Aachen, Germany.
authors.forename: Ha Vinh Lam
authors.initials: HV
authors.lastname: Nguyen
authors.forename: Atef
authors.initials: A
authors.lastname: Jabri
authors.forename: Vinh
authors.initials: V
authors.lastname: Van
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Stahl