Abstract
The mol-ecular salt sulfamethoxazolium {or 4-[(5-methyl-1,2-oxazol-3-yl)sulf-amo-yl]anilinium methyl sulfate monohydrate}, C(10)H(12)N(3)O(3)S(+)·CH(3)O(4)S(-)·H(2)O, was prepared by the reaction of sulfamethoxazole and H(2)SO(4) 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.