Two polymorphs of N-(2,6-difluorophenyl)formamide.

The structures of two distinct polymorphic forms of N-(2,6-difluorophenyl)formamide, C(7)H(5)F(2)NO, have been studied using single crystals obtained under different crystallizing conditions. The two forms crystallize in different space groups, viz. form (Ia) in the orthorhombic Pbca and form (Ib) in the monoclinic P2(1) space group. Each polymorph crystallizes with one complete molecule in the asymmetric unit and they have a similar molecular geometry, showing a trans conformation with the formamide group being out of the plane of the aromatic ring. The packing arrangements of the two polymorphs are quite different, with form (Ia) having molecules that are stacked in an alternating arrangement, linked into chains of N-H...O hydrogen bonds along the crystallographic a direction, while form (Ib) has its N-H...O hydrogen-bonded molecules stacked in a linear fashion. A theoretical study of the two structures allows information to be gained regarding other contributing interactions, such as pi-pi and weak C-H...F, in their crystal structures.