title: (14)N Nuclear Quadrupole Coupling and Methyl Internal Rotation in N-tert-Butylacetamide As Observed by Microwave Spectroscopy.
abstract: The rotational spectrum of N-tert-butylacetamide, CH3(C═O)(NH)C(CH3)3, was measured in the frequency range from 2 to 26.5 GHz using a molecular beam Fourier transform microwave spectrometer. Only one conformer with trans configuration and Cs symmetry was observed. Torsional splittings up to 4.3 GHz occurred in the spectrum due to the internal rotation of the acetyl methyl group CH3(C═O) with a barrier height of approximately 65 cm(-1). Hyperfine structures arise from the quadrupole coupling of the (14)N nucleus appeared for all rotation-torsional transitions. The data set was reproduced with the programs XIAM and BELGI-C1-hyperfine, an extended version of the BELGI-C1 code that includes the effect of the (14)N quadrupole coupling, to root-mean-square deviations of 16.9 and 3.0 kHz, respectively. Quantum chemical calculations were performed to complement the experimental results. The BELGI-C1-hyperfine code was also used to refit the recently published microwave data of N-ethylacetamide to measurement accuracy.
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, D-52074 Aachen, Germany.
authors.forename: Raphaela
authors.initials: R
authors.lastname: Kannengießer
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, D-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, F-94010 Créteil Cedex, France.
authors.forename: Ha Vinh Lam
authors.initials: HV
authors.lastname: Nguyen
authors.affiliation: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université Paris Diderot , 61 avenue du Général de Gaulle, F-94010 Créteil Cedex, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kleiner