Molecular relaxation processes of some halonaphthalenes in a polystyrene matrix

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Abstract
The dielectric absorption of eight halonaphthalenes in a polystyrene matrix has been measured in the frequency range of 102–105 Hz and in two cases also in the range of 2.2×104 to 5×107 Hz 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 2- than the 1-halonaphthalenes while the enthalpies of activation of the latter range between 18–22 kJ mol−1 and for the former 23–41 kJ mol−1. The enthalpy variation between the 1- and 2-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.