Rotational Isomers of the 1-Fluoro-2-haloethanes

The infrared spectra of 1-chloro-2-fluoroethane, 1-bromo-2-fluoroethane, and 1-fluoro-2-iodoethane have been obtained in the solid, liquid, and vapor states. Raman spectra of the liquids are also presented. A complete vibrational-frequency assignment has been made for each of the molecules. The results indicate that the gauche isomer is the more stable in the liquid state whereas the trans form is more stable in the vapor. Enthalpy differences have been determined for each of the molecules in the liquid and vapor states except for gaseous 1-fluoro-2-iodoethane.