Crystal and molecular structures of two polymorphs of 4-methyl-2-nitroacetanilide (MNA)

Abstract

The crystal and molecular structure of white (MNA-1) and yellow (MNA-3) forms of 4-methyl-2-nitroacetanilide have been determined by X-ray diffraction techniques. The crystals of MNA-1 are monoclinic,a=10.421(2),b=9.980(2),c=9.568(2) Å,β=99.51(2)°, space groupP2₁/c,Z=4. Crystals of MNA-3 are triclinic,a=17.956(2),b=12.908(2),c=4.039(1) Å,α=93.13(2)°,β=83.71(2)°, γ=90.77(2)°, space groupP¯1,Z=4. Both structures were solved by direct methods using theShelx-76 system of programs, and refined using full-matrix least squares. The number of unique reflections used in refinement and the finalR values are: MNA-1, 1545, 0.067; MNA-3, 3127, 0.065. The two distinct molecules in MNA-3 have intramolecular hydrogen bonds and different molecular conformations, although both are fairly planar, and each type is closely packed in columns of parallel molecules along thec direction. In MNA-1 the C=O⋯H-N geometry is indicative of intermolecular hydrogen bonding and the molecules adopt a conformation in which the nitro and amide groups lie in planes at approximately 45° to the benzene ring.