Crystallographic characterisation of benzoyl azides. A comparative study

The crystal structures of five benzoyl azides XC6H4C(O)N3 (X ¼ 2-nitro, 4-nitro, 4-cyano, 4-methoxy, 4-dimethylamino) are reported together with the low temperature structure determinations of XC6H4SO2N3 (X ¼ 2-nitro) and XC6H4SO2Cl (X ¼ 2-nitro, 4-nitro). The extensive p delocalisation in benzoyl azides keeps the C(O)N3 moiety in the plane of the phenyl ring and this overall planar conformation is retained by distorting bond angles when steric effects become significant. Strong electron-releasing substituents that also lie in the plane of the phenyl ring result in chinoidally disturbed aromatic systems. The crystal packing of benzoyl azides is mainly affected by short C–H· · ·A interactions and p interactions of stacked aromatic rings. The low temperature reinvestigation of 2-nitrobenzenesulfonyl azide confirmed the existence of dipole–dipole interaction between the nitro, sulfonyl, and azide groups. q 2003 Elsevier B.V. All rights reserved.