crystal structures of three n-(3-acetylphenyl)quinoline-2-carboxamides

In the title compounds, N-(5-acetyl-2-methylphenyl)quinoline-2-carboxamide [C19H16N2O2, (I)], N-(5-acetyl-2-bromophenyl)quinoline-2-carboxamide [C18H13BrN2O2, (II)] and N-(5-acetyl-2-ethynylphenyl)quinoline-2-carboxamide [C20H14N2O2, (III)], the quinoline ring system is essentially planar and forms a dihedral angles of 3.68 (5) (I), 5.59 (7) (II) and 1.87 (6)° (III) with the acetyl-substituted ring. The molecular structures of (I) and (III) each feature an intramolecular N—H...N hydrogen bond, forming an S(5) ring, while in (II) an intramolecular bifurcated N—H...(N,Br) hydrogen bond forms two S(5) rings. In the crystals, weak C—H...O hydrogen bonds link molecules of (I) into C(7) chains long [010], molecules of (II) into chains of R22(8) rings along [110] and molecules of (III) into C(8) chains along [010]. In (I), there are no significant π–π stacking interactions under 4 Å, but in both (II) and (III), π–π interactions link the weak hydrogen-bonded chains into layers parallel to (001) [centroid–centroid disttances of 3.748 (1) Å in (II) and 3.577 (1), 3.784 (1) and 3.780 (1) Å in (III)].