Correlation of Boiling Points with Molecular Structure for Chlorofluoroethanes

Two six-descriptor models, each descriptor derived directly from molecular structure, were fitted to the normal boiling points ( T b ) of ethane plus the 52 known chlorofluoroethanes by multiple linear regression ( s = 2.6 K, R 2 = 0.998). Both models predict T b values of 351 ± 2 and 366 ± 2 K for unknown 1,1-dichloro-2-fluoroethane and 1,1,1-trichloro-2-fluoroethane, respectively. Several descriptors treat specially the atoms that remain exterior after X atoms in CH 2 X groups (X = Cl, F) and H atoms in CHX 2 groups attach electrostatically to identical groups of adjacent molecules. Electrostatic repulsion between opposing C X bonds reduces T b by 20−30 K for half of the compounds.