Methyl internal rotation in the microwave spectrum of vinyl acetate

Ha Vinh Lam Nguyen; Atef Jabri; Vinh Van; Wolfgang Stahl

doi:10.1021/jp5075829

Methyl internal rotation in the microwave spectrum of vinyl acetate

J Phys Chem A. 2014 Dec 26;118(51):12130-6. doi: 10.1021/jp5075829. Epub 2014 Dec 10.

Authors

Ha Vinh Lam Nguyen¹, Atef Jabri, Vinh Van, Wolfgang Stahl

Affiliation

¹ Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, D-52074 Aachen, Germany.

PMID: 25423450
DOI: 10.1021/jp5075829

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.