2-Amino-5-chloro-pyridine-fumaric acid (1/2).

The asymmetric unit of the title compound, C(5)H(5)ClN(2)·0.5C(4)H(4)O(4), comprises a neutral 2-amino-5-chloro-pyridine mol-ecule and one half of a fumaric acid mol-ecule which lies on an inversion center. The dihedral angle between the pyridine ring and the plane formed by the fumaric acid mol-ecule is 3.22 (8)°. The 2-amino-5-chloro-pyridine mol-ecule is planar, with a maximum deviation of 0.004 (1) Å for the pyridine N atom. In the crystal, the 2-amino-5-chloro-pyridine mol-ecules inter-act with the carboxyl groups of fumaric acid mol-ecules through N-H⋯O and O-H⋯N hydrogen bonds, forming centrosymmetric R(2) (2)(8) ring motifs and another N-H⋯O hydrogen bond links these motifs into a two-dimensional network parallel to (100).