| Abstract
| - Isochoric and isobaric freezing of 1,1-dichloroethane, CH3CHCl2, mp = 176.19 K, yielded the orthorhombicstructure, space group Pnma, with the fully ordered molecules, in the staggered conformation, located onmirror planes. The CH3CHCl2 ambient-pressure (0.1 MPa) structures were determined at 160 and 100 K,whereas the 295 K high-pressure structures were determined at 0.59 and 1.51 GPa. At 0.1 MPa, allintermolecular distances are considerably longer than the sums of the van der Waals radii, and only a pressureof about 1.5 GPa squeezed the Cl···Cl and Cl···H contacts to distances commensurate with these sums. Theexceptionally large difference between the melting points of isomeric 1,1- and 1,2-dichloroethane can berationalized in terms of their molecular-packing efficiency. It has been shown that the location of atoms inmolecules affects their intermolecular interactions, and hence their van der Waals radii are the function ofmolecular structures.
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