Conformational polymorphs of 1,1,2,2-tctrachloroethane: pressure vs. temperature

摘要

Directional Cl- • Cl type I and II interactions govern the low-density aggregation of 1,1,2,2-tetrachloroethane molecules in synclinal conformation in the crystalline state at low temperature, whereas the dense molecular packing in high-pressure is achieved for the antiperiplanar conformers and electrostatically less favored Cl - Cl contacts. The mechanism of transformation between loose and dense associations involves the collapse of Cl- - Cl contacts and conformational conversion. Molecular conformation is the key factor in the structure-property relation of substances with flexible molecules-either as simple as ethanes and as complex as proteins.1 In the gas and liquid states, molecules either assume one preferred conformation, or an equilibrium of two or more conformations is observed.