The crystal structure of 1,2,4-trichloro-3,5,6-trimethylbenzene

Abstract

Crystals of 1,2,4-trichloro-3,5,6-trimethylbenzene are monoclinic, a= 17·31, b= 3·88, c= 8·22 Å, β= 119·55°, space-group P2₁/a, Z= 2, so that the molecule possesses a crystallographic centre of symmetry. The structure was determined with Mo-K_α counter data by Patterson, electron-density, and least-squares methods, the final R being 0·09 for 504 observed reflexions. The crystal exhibits an orientational disorder, the chlorine atoms and methyl groups being distributed randomly so that the molecule has apparently six-fold symmetry. The observed disorder, and previous n.m.r. data, can be interpreted in terms of discontinuous molecular reorientations, which are a consequence of relatively large rigid-body oscillations.