CONFORMATIONAL-ANALYSIS, AB-INITIO CALCULATIONS, AND VIBRATIONAL ASSIGNMENT OF 3-CHLOROPROPIONITRILE

Raman (3200 to 10 cm-1) and infrared (3200 to 400 cm-1) spectra have b een recorded for liquid and solid 3-chloropropionitrile, ClCH2CH2CN. T hese data are interpreted on the basis that the molecule exists as a m ixture of trans (Cl atom oriented trans to the CN group) and gauche co nformers in the liquid phase with the gauche form the more stable rota mer and the only conformer in the solid. From variable temperature Ram an studies of the liquid, the enthalpy difference between conformers i s determined to be 609 +/- 31 cm-1 (1.74 +/- 0.09 kcal mol-1). A compl ete vibrational assignment is proposed for both conformers. We have ca rried out ab initio calculations employing the MP2/6-31G basis set to obtain the structural parameters, barriers to internal rotation, the fundamental frequencies for both conformers, and the infrared and Rama n intensities. The calculated values are compared with the correspondi ng experimental quantities. These results are discussed and compared w ith similar quantities obtained for some related molecules.