2-Azido-1-(4-methyl-phen-yl)ethanone.

In the mol-ecule of the title compound, C(9)H(9)N(3)O, the angle formed by the least-squares line through the azide group with the normal to the plane of the benzene plane ring is 46.62 (16)°. The crystal structure features C-H⋯O hydrogen bonds, which link the mol-ecules into zigzag chains running parallel to [010].

2-Azido-1-(4-nitro-phen-yl)ethanone.

In the title compound, C(8)H(6)N(4)O(3), the ketone [C-C(=O)-C] and nitro groups are tilted with respect to the benzene ring by 18.92 (6) and 24.11 (15)°, respectively. In the crystal, mol-ecules are linked into inter-woven chains running parallel to the [100] direction by C-H⋯N hydrogen bonds and weak π-π stacking inter-actions, with centroid-centroid separations of 3.897 (3) Å.

2-Azido-1-(4-fluoro-phen-yl)ethanone.

The crystal structure of the title compound, C(8)H(6)FN(3)O, is stabilized by C-H⋯O hydrogen bonds, which link the mol-ecules into chains running parallel to the a axis.