Orientational disorder in 4-chloronitrobenzene

The crystal structure of 4-chloro­nitro­benzene, C6H4ClNO2, a material that exhibits disorder in the solid state, is re-examined using multiple-temperature single-crystal X-ray diffraction. Our results show a marked improvement on previous crystal structure determinations and our comprehensive multiple temperature measurements help to rationalize the structural anomalies. 4-Chloro­nitro­benzene exhibits twofold orientational disorder of the NO2/Cl substituents, with the mol­ecule lying across an inversion centre. There is also evidence of large thermal motion, which exists at all temperatures and reflects the presence of significant disorder in this material. The nitro group shows possible libration, with one O atom exhibiting larger thermal motion than the other across the whole temperature range. This is explained by a difference in hydrogen-bonding environment.