Rotational isomerism in 1,1′-dicyanobicyclopentyl, 1,1′-dicyanobicyclohexyl, and 1,1 '-dicyanobicycloheptyl

Abstract

I.r. spectra of 1,1 '-dicyanobicyclopentyl, 1,1 '-dicyanobicyclohexyl, and 1,1 '-dicyanobicycloheptyl in the solid and solution states, and Raman spectra in the solid state are reported and assignment of frequencies made. Dipole moments in different solvents (benzene, carbon tetrachloride, and dioxane) at different temperatures and molar Kerr constants (in carbon tetrachloride and benzene) are also reported. Analysis of the dielectric data shows that, at 25 °C, the compounds in the series exist as rotameric mixtures in carbon tetrachloride solution containing 4.5, 11, and 38% respectively of the gauche rotamer. Benzene causes the gauche population to increase, as evidenced by the dipole moment and Kerr constant values in this solvent. Comparison of the Raman and i.r. spectra of the solids suggests that all three compounds exist in the trans conformation in the solid state.