Structure–property relations in chloroacetonitriles

Abstract

The thermodynamic characteristics of acetonitrile, mono-, di- and tri- chloroacetonitriles have been rationalized in terms of molecular association and weak intermolecular forces. In this series acetonitrile and trichloroacetonitrile melt and boil at the lowest temperature and their enthalpies of vaporization are the lowest. The highest magnitudes of these parameters are those of monochloroacetonitrile. This trend coincides with the most balanced distribution of electrostatic potential (i.e. nearly equal magnitudes of the maximum and minimum potential) on the molecular surface for this compound. The chloroacetonitriles have been in situ pressure-frozen and their structures determined at room temperature by single-crystal X-ray diffraction at 1.30(5) GPa, 1.00(5) GPa and 0.90(5) GPa, for chloro-, dichloro- and trichloroacetonitrile, respectively. In their structures weak CH⋯N hydrogen bonds are gradually replaced by Cl⋯N and Cl⋯Cl interactions.