Crystal structure of 4-[(5-methyl-isoxazol-3-yl)amino-sulfon-yl]anilinium 3,5-di-nitro-salicylate

Synthesis, crystal structure and Hirshfeld surface analysis of sulfamethoxazolium methyl-sulfate monohydrate

The mol-ecular salt sulfamethoxazolium {or 4-[(5-methyl-1,2-oxazol-3-yl)sulf-amo-yl]anilinium methyl sulfate monohydrate}, C10H12N3O3S+·CH3O4S-·H2O, was prepared by the reaction of sulfamethoxazole and H2SO4 in methanol and crystallized from methanol-ether-water. Protonation takes place at the nitro-gen atom of the primary amino group. In the crystal, N-H⋯O hydrogen bonds (water and methyl-sulfate anion) and inter-molecular N-H⋯N inter-actions involving the sulfonamide and isoxazole nitro-gen atoms, link the components into a tri-dimensional network, additional cohesion being provided by face-to-face π-π inter-actions between the phenyl rings of adjacent mol-ecules. A Hirshfeld surface analysis was used to verify the contributions of the different inter-molecular inter-actions, showing that the three most important contributions for the crystal packing are from H⋯O (54.1%), H⋯H (29.2%) and H⋯N (5.0%) inter-actions.

A thermodynamic relationship and phase transition study involving two polymorphs of sulfamethoxazole: form I vs. form II

Two sulfamethoxazole polymorphs (form I and II) have been studied. The form II → form I transformation is observed via milling and dissolution in acetonitrile. A phase transition mechanism is proposed based on their supramolecular geometries.

de Melo C, Doriguetto AC. Sulfamethoxazole salts: crystal structures, conformations and solubility

Novel salts of the antibiotic sulphamethoxazole were obtained and characterized, effectively showing enhanced solubility.