CONFORMATIONAL STABILITY AND STRUCTURAL PARAMETERS OF 3-FLUOROPROPENE AND SOME SUBSTITUTED DERIVATIVES

From variable temperature studies of the vibrational spectra of gaseous and/or liquid 3-fluoropropene and some substituted derivatives, the conformational enthalpy differences have been determined. Substitution of an electronegative group at the 2-position enhances the stability of the cis conformer whereas methyl substitution enhances the stability of the gauche conformer. The stability and structural parameters of 3-fluoropropene have been obtained from ab initio calculations employing the MP2/6-31G* basis set. Complete r0 structural parameters have been obtained for both conformers from a combination of restricted C-H distances from the ab initio values and previously reported rotational constants from eight isotopomers.