4-Fluoro-N-methyl-N-nitroaniline

Molecules of the title compound, C7H7FN2O2, are composed of a nitramine group which is twisted with the respect to the aromatic ring, with an N—N—C—C torsion angle of −117.38 (12)°. In the molecule, the N—N bond length [1.3510 (15) Å] indicates some double-bond character, while the angle between the aromatic ring and the nitramine group rules out further delocalization in the molecule. In the crystal, C—H...F hydrogen bonds connect the molecules into C11(6) chains along the a axis. C—H...O hydrogen bonds form, which feature R22(12) loops and further connect these chains

Acetylhydroxamic acid

There is one independent molecule in the asymmetric unit of the title compound (alternatively named N-hydroxyacetamide), C2H5NO2. It crystallizes in the noncentrosymmetric space group P43. The structure is an anhydrous form of acetylhydroxamic acid with typical geometry that corresponds well with the hydrated structure described by Bracher & Small [Acta Cryst. (1970), B26, 1705–1709]. In the crystal, N—H...O and O—H...O hydrogen bonds connect the molecules into chains in the c-axis direction

N,N-Dicyclohexylnitramine

Molecules of the title compound, C12H22N2O2, are composed of an nitramine group substituted by two cyclohexane rings. The cyclohexane rings have chair conformations, with the exocyclic C—N bonds in axial orientations. In the crystal, C—H...O hydrogen bonds connect the molecules into C(6) [-101] zigzag chains

Theoretical Multipolar Atom Model Transfer in Nitro-Derivatives of <i>N</i>‑Methylaniline

The nitroanilines are an example of compounds in which the coexistence of electron-rich and electron-deficient substituents, connected through a conjugated π-electronic system, makes their molecular second-order hyperpolarizability and second-harmonic generation efficiency particularly high. This property makes them extremely interesting from the point of view of charge density distribution analysis. The electron density of three isomeric molecules, i.e., <i>N</i>-methyl-2-nitroaniline, <i>N</i>-methyl-3-nitroaniline, and <i>N</i>-methyl-4-nitroaniline, was calculated theoretically through the multipolar atom model transfer. Two types of refinement models, i.e., multipolar atom model (MAM) and independent atom model (IAM), have been applied for analysis of model improvement concerning the electron-density parameters transfer. It results in a more precise molecular structure in terms of geometry and thermal displacement parameters along with a reduction of statistical refinement factors and residual electron densities. The proposed approach enables the extraction of relevant electron density-derived information, where the intrinsic quality of X-ray data does not allow a “true” multipolar refinement. The effect of ortho-, meta-, and para-substitution on π-electron distribution and aromaticity of the nitroaniline ring was compared using harmonic oscillator model of aromaticity (HOMA) and nucleus independent chemical shift (NICS) indexes. In the paper, the electronic effects from the charge density parameters have been examined along with the study of intermolecular interactions using two different approaches: one, based on the Hirschfeld surfaces analysis, and the second, based on the dissociation energy estimation from topological analysis