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

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, r -structural parameters of the respective methyl group could be determined, thus allowing us to consider the influence of methyl substitution on the N-quadrupole coupling tensor and the structural relevance of the internal rotor angle given by torsional analysis. N nuclear quadrupole hfs and IAM methyl torsional analyses were redone with the correct rotational constants.