A triclinic polymorph of benzanilide: disordered molecules form hydrogen-bonded chains

In the P (1) over bar polymorph of benzanilide or N-phenylbenzamide, C13H11NO, the molecules are linked into simple C(4) chains by N-H...O hydrogen bonds. The molecules exhibit orientational disorder, but the donor and acceptor in a given hydrogen bond may occur, independently, in either the major or the minor orientation, such that all four possible N-H...O combinations have very similar geometries. The structure of this P (1) over bar polymorph can be related to that of a previously reported C2/c polymorph.