7‐Carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate at 100 K

Both 7‐carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate, C₁₁H₉NO₃·H₂O, (I), and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate, C₁₁H₁₀NO₃⁺·Cl^?·H₂O, (II), crystallize in the centrosymmetric P space group. Both compounds display an intramolecular O—H?O hydrogen bond involving the hydroxy group; this hydrogen bond is stronger in (I) due to its zwitterionic character O?O = 2.4449 (11) Å in (I) and 2.5881 (12) Å in (II)]. In both crystal structures, the HN⁺ group participates in the stabilization of the structure via intermolecular hydrogen bonds with water mol­ecules N?O = 2.7450 (12) Å in (I) and 2.8025 (14) Å in (II)]. In compound (II), a hydrogen‐bond network connects the Cl^? anion to the carboxylic acid group Cl?O = 2.9641 (11) Å] and to two water mol­ecules Cl?O = 3.1485 (10) and 3.2744 (10) Å].