Two polymorphs of N , N '-diphenyl-2-[1-(propyl-amino)-ethyl-idene]propanedi-amide.

Two polymorphs of the title compound, C 20 H 23 N 3 O 2 , have been isolated. Polymorph ( I ) crystallizes in the monoclinic space group P2 1 / n and polymorph ( II ) in the tetra-gonal space group I4 1 / a . The main difference between the two polymorphs on the mol-ecular level is the orientation of the n -propyl group. This group is anti-periplanar in ( I ) and synclinal in ( II ). The core of the mol-ecule consists of two carbamoyl units bound to an enamine unit. The most prominent features are intra-molecular N-H⋯O hydrogen bonds in both polymorphs. Both polymorphs form dimers with graph set R 2 2 (12) via inter-molecular N-H⋯O hydrogen bonds. Adjacent dimers of ( I ) are connected via a weak C-H⋯O inter-action, resulting in a chain parallel to the crystallographic a -axis. The dimers of ( II ) are connected by weak C-H⋯π inter-actions, forming inter-molecular chains along the c -axis direction.