A monoclinic polymorph of chloro-thia-zide.

A new polymorph of the diuretic chloro-thia-zide, 6-chloro-1,1-dioxo-2 H -1,2,4-benzo-thia-zine-7-sulfonamide, C 7 H 6 ClN 3 O 4 S 2 , is described. Crystallized from basic aqueous solution, this monoclinic polymorph is found to be less thermodynamically favoured than the known triclinic polymorph and to feature only N-H⋯O type inter-molecular hydrogen bonds as opposed to the N-H⋯O and N-H⋯N type hydrogen bonds found in the P 1 form.