INFLUENCE OF CRYSTAL ENVIRONMENT ON MOLECULAR-CONFORMATION - P-BROMO-N-(P-DIMETHYLAMINOBENZYLIDENE)ANILINE

p-Bromo-N-(p-dimethylaminobenzylidene) aniline, C15H15BrN2, (1), compr ises two independent molecules with markedly different conformations. Molecule A is essentially planar along its entire length (including th e dimethylamino group) whereas molecule B deviates considerably from p lanarity with an interplanar angle of 145.8 (3)degrees between the two phenyl rings and the NMe(2) group twisted by 10 (2)degrees out of the plane of the phenyl ring to which it is bound. While polymorphism and crystal packing effects are well documented for benzylidene derivativ es, this is an interesting example with two quite distinct conformatio ns in the same crystal phase. The differences are accounted for in ter ms of crystal-packing effects. The structure highlights the ability of particular molecular arrangements to stabilize a less favourable mole cular conformation.