Structure of N,4-dinitroaniline and its complex with sulfolane at 85 K; on the proton donor-acceptor affinity of the primary nitramine (HNNO2) group

摘要

The NNO2 group of the title compound is significantly less twisted with respect to the aromatic ring in comparison to a typical secondary nitramine. The amide nitrogen is trigonally hybridized. The nitramino group is almost planar. The C-C- N-N torsion angles vary between ca 13 and 42degrees, whereas the twist along the N-N bond is much smaller and amounts to between ca 1 and 15degrees. Those twist angles are governed by a crystal packing and are much larger in the case of crystals of pure N,4-dinitroaniline in comparison to that of its complex with sulfolane. The deviations of the internal angles of the aromatic ring from 120degrees do not exceed 3degrees. The presence of the nitro group increases the C-C-C valence angle of ca 2.0- 2.6degrees, whereas an analogous effect associated with the nitramino group is much smaller (ca 0.3-1.3degrees), pointing to its weak electron-withdrawing properties. The nitramino group displays no tendency to conjugate with an electron-demanding substituent across the ring. It participates in hydrogen bonding only as a hydrogen-bonding donor. It does not act as a proton acceptor, despite the fact that nitramine rearrangement is catalysed by acids. [References: 25]