DIELECTRIC STUDIES .21. RELAXATION PROCESSES OF SOME HALOETHANES IN P-XYLENE SOLUTION

The dielectric absorption of several haloethanes in p-xylene solution has been determined at microwave frequencies and the static dielectric constant at 2 Mc/sec. The dielectric data have been used to yield mean relaxation times and apparent dipole moments. All of the compounds which have been measured exhibit an appreciably longer measured relaxation time in p-xylene than in cyclohexane solution. This indicates that the free energy of activation for molecular reorientation is increased, probably by weak hydrogen bonds formed between the hydrogen of the substituted ethane and the π-electron cloud of the p-xylene. Interaction is also apparent from the difference between their apparent dipole moments in the two solvents and may be dependent upon the volume of the molecule and the protonic character of the hydrogen atoms within the haloethane.