Abstract
3-(2-Bromo-4-(1-methylethyl)phenyl)-1,1-dimethylurea was synthesized and structurally characterized at 296 K, 200 K and 140 K. A reversible thermal phase transformation was observed at -170-180 K. On cooling, the structure transforms from a monoclinic to a triclinic crystal system. The isopropyl group is disordered above the phase transition temperature but is ordered below the transition temperature.