STABILIZATION OF A HIGH-ENERGY MOLECULAR-CONFORMATION BY SPECIFIC INTERMOLECULAR FORCES, A NOVEL PLANAR BENZYLIDENEANILINE SYSTEM

The system containing six benzylideneanilines (BA) has been studied: G roup 2: I: N-(p-Chlorobenzylideneaniline)m-chloroaniline (BA, X = 4 - Cl, Y = 3 - Cl) II: N-(p-Bromobenzylideneaniline)m-bromoaniline (BA, X = 4 - Br, Y = 3 - Br) III: N-(p-Bromobenzylideneaniline)m-chloroanili ne (BA, X = 4 - Br, Y = 3 - Cl)IV: N-(p-Chlorobenzylideneaniline)m-bro moaniline (BA, X = 4 - CI, Y = 3 - Br) Group 2: V: N-(m-Chlorobenzylid eneaniline)p-bromoaniline (BA, X = 3 - Cl, Y = 4 - Br) VI: N-(m-Bromob enzylideneaniline)p-chloroaniline (BA, X = 3 - Br, Y = 4 - Br) The cry stal structures of Group are isostructural. They crystallize in a mono clinic cell, space group P2(1). They are rare examples of planar benzy lideneanilines in a nondisordered crystal structure. The crystal struc tures exhibit an intermolecular ring containing five atoms and hal---h al, C-H---hal interactions, which may contribute to the planarity of t he molecule. The structures in Group 2 crystallize in a monoclinic cel l, space group P2(1)/c. The conformation is nonplanar and there are no intermolecular halogen---halogen interactions. The abovementioned fiv e atom pattern ring does not occur in these structures. These two grou ps of structures show that the type and mode of molecular substitution can lead to specific intermolecular interactions which in turn stabil ize an otherwise unfavorable molecular conformation.