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.