A comparative spectroscopic investigation of two polymorphs of 4′-methyl-2′-nitroacetanilide using solid-state infrared and high-resolution solid-state nuclear magnetic resonance spectroscopy

Solid-State Nuclear Magnetic Resonance Spectroscopy-Pharmaceutical Applications

“…In a series of publications by Harris and Fletton, solid‐state NMR spectroscopy was used to investigate the structures of several polymorphs 151–155. The majority of these studies included X‐ray diffraction and IR techniques and also addressed the possibility of quantitative measurements of polymorphic mixtures.…”

“…In this case, the crystallographic splittings were noted for the two forms and were correlated with hydrogen bonding. An identical approach was used to study a pharmaceutical polymorphic structure in the investigation of the two polymorphs of 4′‐methyl‐2′‐nitroacetanilide 153. An additional study of cortisone acetate154,155 by solid‐state NMR spectroscopy revealed differences in the NMR spectra for the six crystalline forms.…”

Colour Polymorphism of a Bis(quinoxaline) Compound

“…benzylidene rings form an angle of 24.8°with the plane Fletton et al [5] have described an intermolecular hydro-formed by the two bridge atoms and the two other nonhygen-bonding system in one (colourless) polymorphic form drogen atoms directly connected to them. The crystals of of a nitroacetanilide derivative, and an intramolecular ar-the first form are described as pale-yellow, while those of rangement in a second (yellow) form.…”

Solid‐state NMR and computational studies of 4‐methyl‐2‐nitroacetanilide

“…The 50-MHz 13 C CP/MAS spectra of MNA (both white and yellow forms) have been reported previously. 31 The solid-state chemical shifts presented here consistently differ by 0.5-1.0 ppm from those given in the earlier paper, 31 probably because of differing referencing procedures. Assigning the peaks for the white form, with the assistance of solution-state data and a dipolar dephasing experiment, is straightforward, especially because substantial splittings for carbons C1 and C8, resulting from coupling to 14 N, 32 are prominent (and a broadening from this cause is seen for C2).…”

“…The main region of the spectrum for the yellow form is significantly more crowded than that for the white form, partly because of the existence of two independent molecules for the former but also because the white form is substantially less planar, giving decreased resonance in the molecular structure. Table 2 lists the 13 C CP/MAS shifts, together with those for a solution in CDCl 3 , 31 including assignments. The 50-MHz 13 C CP/MAS spectra of MNA (both white and yellow forms) have been reported previously.…”