A Reanalysis of 14N Nuclear Quadrupole Coupling and Methyl Internal Rotation in the Rotational Spectra of Monomethyl Oxazoles and Isoxazoles

Abstract

Abstract Previously published rotational frequencies of 2-, 4-, and 5-methyl oxazole and of 3- and 5-methyl isoxazole are reanalysed to obtain correct rotational constants (A constants in the first place) on the basis of hypothetically unsplit rotational centre frequencies. With these, r0-structural parameters of the respective methyl group could be determined, thus allowing us to consider the influence of methyl substitution on the 14N-quadrupole coupling tensor and the structural relevance of the internal rotor angle given by torsional analysis. 14N nuclear quadrupole hfs and IAM methyl torsional analyses were redone with the correct rotational constants.