Dielectric Absorption in Crystalline Pentachloronitrobenzene

Abstract

Abstract Dielectric measurements have been performed with pentachloronitrobenzene in polycrystalline state using a trans-former bridge, between 30 Hz and 1 MHz and in the temperature range 20–99°C. The substance shows distinct dielectric absorption in the frequency and temperature ranges, presumably due to molecular rotation in the solid state similar to that of pentachlorotoluene and 1,2,4-trimethyl-3,5,6-trichlorobenzene as has been found by Turney. The frequency factor and the energy of the barrier for the rotation are logA=15.2 (A in sec−1) and ΔH=16.1 kcal/mol. A possible mechanism for the rotational transition of the molecule in the crystalline lattice has been discussed. The dipole moment of this substance in benzene solution has been measured, the result being μ=2.33 Debye.