Abstract
The structures of N-(2-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide and N-(4-chlorophenyl)-4-hydroxy- 2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide, both C16H13ClN2O4S, are stabilized by extensive intramolecular hydrogen bonds. The 4-chloro derivative forms dimeric pairs of molecules lying about inversion centres as a result of intermolecular N-H center dot center dot center dot O hydrogen bonds, forming 14-membered rings representing an R-2(2)(14) motif; the 2-chloro derivative is devoid of any such intermolecular hydrogen bonds. The heterocyclic thiazine rings in both structures adopt half-chair conformations.