Temperature dependence of chlorine nuclear quadrupole resonance and internal motions in o-chloro-, m-chloro-, 2-chloro-5-nitro- and 4-chloro-3-nitro-benzoic acids

Abstract

Based on crystal structure data, the torsional molecular motions (in solids) in four substituted benzoic acids are discussed in the light of nuclear (³⁵Cl) quadrupole resonance results. The torsional frequencies show anonlinear variation with temperature and compare reasonably well with the Raman data on the parent compound. The average temperature coefficient of these motions has been evaluated by Brown's method as well as using Bayer's model. The torsional frequencies in the ortho-chloro substituted compounds do not vary smoothly with temperature.