On the deprotonation of chlorothiazide.

Three alkali metal salt forms of the diuretic chlorothiazide (systematic name: 6-chloro-1,1-dioxo-2H-1,2,4-benzothiazine-7-sulfonamide, HCTZ) are described. When crystallized from aqueous solution, the Na and K salts, namely, poly[[μ-aqua-aqua(μ-6-chloro-1,1-dioxo-7-sulfamoyl-2H-1,2,4-benzothiadiazin-2-ido)sodium] hemihydrate], {[Na(CHClNOS)(HO)]·0.5HO}, and poly[[diaqua(μ-6-chloro-1,1-dioxo-7-sulfamoyl-2H-1,2,4-benzothiadiazin-2-ido)potassium] hemihydrate], {[K(CHClNOS)(HO)]·0.