A VALENCE FORCE FIELD FOR THIOPHENE AND ITS DEUTERIUM AND METHYL DERIVATIVES

To obtain reliable vibrational assignments for use in statistical thermodynamic calculations, a valence force field was derived from 300 observed vibrational wavenumbers of thiophene, 8 deuterium derivatives, and 6 methyl derivatives. Of the 45 force constants, 25 were adjusted to fit the a1, b1, and a′ fundamentals; 14 were adjusted to fit the a2, b2, and a″ fundamentals; and 6 pertaining to the methyl group were transferred from other molecules. The mean deviation of the calculated wavenumbers from the observed ones was 7.3 cm-1 or 0.73% for the a1, b1, and a′ species and 2.6 cm-1 or 0.46% for the a2, b2, and a″ species. A vibrational assignment proposed in the literature for the parent compound was substantiated, and reliable vibrational assignments were obtained for the two monomethyl and four dimethyl derivatives. © 1969.