2-(Carboxy­methyl­sulfan­yl)pyridine-3-carboxylic acid monohydrate

The title compound, C(8)H(7)NO(4)S·H(2)O, was obtained by reaction of 2-mercaptopyridine-3-carboxylic acid with chloro­acetic acid. In the mol­ecular structure, the dihedral angle between the two least-squares planes defined by the pyridine ring and the carb­oxy group is 8.32 (9)°. The carboxy­methyl­sulfanyl group makes a torsion angle of 82.64 (12)° with the pyridine ring. An intra­molecular O—H⋯N hydrogen bond between the acidic function of the carboxy­methyl­sulfanyl group and the pyridine N atom stabilizes the conformation, whereas inter­molecular O—H⋯O hydrogen bonding with the uncoordinated water mol­ecules is responsible for packing of the structure, leading to chains propagating in [001].