The enthalpies of combustion of alpha-, beta-, gamma- and delta-1,2,3,
4,5,6-hexachlorocyclohexane (HCCH) isomers and of chlorocyclohexane (C
CH), and the enthalpy of vaporization of CCH have been determined by p
recision combustion and vaporization calorimetry; the enthalpies of fo
rmation of these compounds are derived. These results are more reliabl
e than values reported in the literature. The non-bonding interactions
in these molecules are discussed using the group scheme, the electros
tatic bond energy model and force field calculations.