The temperature variation of the nuclear quadrupole resonance frequencies in 3,4-dichloro-aniline and 2,6-dichloro-aniline were fitted to three different models available in literature, namely the Kushida model, the Brown model, and a fourth order polynomial. Brown's model with T 0 = 205 K gave the best fit in the case of both compounds indicating that the temperature dependence of the torsional frequencies cannot be neglected in these compounds. The internal torsional frequencies were

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... from the nuclear quadrupole resonance data by using a two-mode approximation in a temperature range of 77-300 K for the above two compounds. The torsional frequencies lie in a range of 30-60 cm −1 in both compounds and agree closely with the Raman lines obtained in 2,6-dichloro-aniline. The lower frequency mode around 37 cm −1 may be associated with the motion around an axis perpendicular to the benzene ring which is present in both compounds.