The dielectric absorption of eight halonaphthalenes in a polystyrene matrix has been measured in the frequency range of 102ndash;105Hz and in two cases also in the range of 2.2times;104to 5times;107Hz and the enthalpy of activation for the molecular relaxation process determined by using the Eyring rate expression. The relaxation time and enthalpy of activation vary as the inclination of the dipole to the principal axes is altered. In fact, the relaxation time is appreciably longer for the 2hyphen; than the 1hyphen;halonaphthalenes while the enthalpies of activation of the latter range between 18ndash;22 kJ molminus;1and for the former 23ndash;41 kJ molminus;1. The enthalpy variation between the 1hyphen; and 2hyphen;halonaphthalenes is to be contrasted with the behavior of quinoline and isoquinoline in Nujol solution where the solute molecules have virtually identical enthalpies of molecular reorientation.
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