The crystal and molecular structure of N-methyl-2,4,6-trinitroacetanilide

N-Methyl-2,4,6-trinitroacetanilide (C₉H₈N₄O₇, N-acetyl-N-methyl=2,4,6-trinitroaniline or AM 246) forms crystals with the monoclinic space group P2₁/c and with unit-cell constants a = 7.813 ± 0.002, b = 8.667 ± 0.002, c = 17.990 ± 0.001 Å and β = 100.521 ± 0.006°. There are four molecules per unit cell. The data were collected by the θ–2θ scan technique on a G. E. XRD-5 diffractometer employing Ni-filtered Cu Kα radiation. The structure was solved by the symbolic addition procedure and was refined by conventional least-squares and Fourier techniques to a final weighted R (based on F²) of 0.027 for 2377 independent reflections. The acetyl group is in the endo conformation, with the carbonyl oxygen extending towards the aromatic ring. The nitro groups at the 2, 4 and 6 positions are rotated 54, 4 and 36°, respectively, out of the plane of the benzene ring. The planar amide group is rotated 60° out of the plane of the aromatic ring. These rotations all have the same sense. The shortest intermolecular distances all appear to be normal van der Waals contacts except for a `weak' hydrogen bond between the carbonyl oxygen and one of the picryl hydrogens of a neighboring molecule.