ROTATIONAL ISOMERISM IN 1-FLUORO-1,1,2,2-TETRACHLOROETHANE

Author Institution: Chemistry Division, U. S. Naval Research Laboratory“The infrared spectra of liquid, vapor and solid $CHCl_{2}$ $CFCl_{2}$ have been studied in the 2-15 $\mu$ region. Two isomeric species are present in the vapor and liquid whereas only one form persists in the crystalline solid. From the temperature dependence of the band intensities the heat of reaction, $\Delta H^{\circ}$ for the liquid and vapor are found to be 0.42 and 0.82 keal/mole, respectively. On the basis of this observed difference in $\Delta H^{\circ}$ for the two states and calculated dipole moments it is concluded that the more stable isomer, which also persists in the crystalline solid, is the skew isomer ($C_{1}$ symmetry). The less stable or higher energy form is the pseudo-trans form ($C_{1}$ symmetry).