2-Amino-4-methyl-pyridinium (E)-3-carb-oxy-prop-2-enoate

In the title salt, C(6)H(9)N(2) (+)·C(4)H(3)O(4) (-), the dihedral angle between the pyridine ring and the plane formed by the hydrogen fumarate anion is 85.67 (6)°. Excluding the amino and methyl groups, the atoms of the cation are coplanar, with a maximum deviation of 0.005 (1) Å. In the crystal structure, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms of the anion via a pair of N-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. These motifs are further connected through N-H⋯O and C-H⋯O hydrogen bonds, leading to a supra-molecular chain along the c axis. These chains are further cross-linked via a pair of O-H⋯O hydrogen bonds involving centrosymmetrically related hydrogen fumarate anions, forming a two-dimensional network parallel to (101). These planes are further interconnected by O-H⋯O interactions into a three-dimensional network.