+2C3H3O4C3H4O4

R factor = 0.046; wR factor = 0.130; data-to-parameter ratio = 17.0. The asymmetric unit of the title compound, 2C10H11N2 2C3H3O4 C3H4O4, consists of one 5-amino-6-methylquinolin-1-ium cation, one hydrogen malonate (2-carboxyacetate) anion and one-half molecule of malonic acid which lies on a twofold rotation axis. The quinoline ring system is essentially planar, with a maximum deviation of 0.062 (2) A ̊ for all non-H atoms. In the anion, an intramolecular O—H O hydrogen bond generates an S(6) ring. In the crystal, the components are linked via N—H O and O—H O hydrogen bonds into layers parallel to the ac plane. The crystal structure also features weak C—H O hydrogen bonds and a – stacking interaction with a centroid–centroid distance of 3.8189 (10) Å. Related literature For background to and the biological activity of quinoline derivatives, see: Sasaki et al. (1998); Reux et al. (2009); Morimoto et al. (1991); Markees et al. (1970). For relate