Temperature Dependence of Internal Torsional Frequencies in 3,4-Dichloro Nitrobenzene and 4-Chloro 2 Nitrophenol Using NQR Data

The temperature variation of the nuclear quadrupole resonance frequency in the two compounds 3,4-dichloro nitrobenzene and 4-chloro 2 nitrophenol were analyzed in the light of the Kushida and Brown models. The internal torsional frequencies at each temperature was calculated using Bayer's model with Tatsuzaki correction under a two-mode approximation to obtain the temperature variation of the torsional frequencies in both compounds. The torsional frequencies are seen to lie between 25 $cm^{-1}$ and 85 $cm^{-1}$ in the first compound and between 30 $cm^{-1}$ and 42 $cm^{-1}$ in the case of the second compound. The temperature dependence of the torsional frequencies is linear above 150 K in the first compound and is linear throughout the range 77 K to 350 K in the second. The smaller temperature dependence in the second compound may be the effect of hydrogen bonding in this compound.