A new polymorph of N-(6-methylpyridin-2-yl)mesitylenesulfonamide.

A new polymorph is reported of the pharmaceutically active sulfapyridine derivative, N-(6-methylpyridin-2-yl)mesitylenesulfonamide, in the zwitterionic form 2-methyl-6-{[(2,4,6-trimethylbenzene)sulfonyl]azanidyl}pyridin-1-ium, C15H18N2O2S. The observed dimorphism is solvent dependent. The phase described previously [Beloso, Castro, García-Vázquez, Pérez-Lourido, Romero & Sousa (2003). Z. Anorg. Allg. Chem. 629, 275-284] crystallizes from ethanol and several other organic solvents, whereas the new form described here is obtained as a phase-pure product from methanol. The molecules in both dimorphic phases are very similar and adopt the conformation which is also predicted for an individual molecule by force field calculations. However, the two forms differ in their packing and hydrogen bonding. Results from solvent-assisted grinding indicate that the new form is less stable than the previously published phase.