Microwave Absorption and Molecular Structure in Liquids. LX. Intramolecular Relaxation Mechanisms in Aromatic Ethers and Several Related Molecules

Abstract

The dielectric constants and losses of 11 aromatic ethers and related compounds in dilute benzene solution have been measured at wavelengths between 1.25 and 50 cm at temperatures from 20° to 60°. The substances measured are dibenzyl ether, benzyl phenyl ether, dicyclohexyl ether, 2-nitrophenyl phenyl ether, m-diphenoxybenzene, 4-bromophenyl phenyl ether, 4-biphenyl phenyl ether, phenoxathiin, thianthrene, triphenylphosphine, and triphenylchloromethane. The dielectric relaxation times calculated from these data indicate that most of the seemingly small values obtained result from combination of short, coupled, ring rotations with over-all molecular rotation. Comparison of the dipole moment values calculated for twenty-three substituted phenyl ethers with the observed values gives no evidence of the large mesomeric moments seemingly necessary to make mesomeric charge shift a generally important factor in lowering the relaxation times of these molecules. The low relaxation time found for phenoxathiin probably results from combination of dipole orientation by a ``butterfly motion'' of the nonplanar molecule with orientation by over-all molecular rotation.