2-Amino-5-methylpyridinium 4-methylbenzoate

The 4-methylbenzoate anion of the title salt, C6H9N2 +·C8H7O2 −, is nearly planar, with a dihedral angle of 6.26 (10)° between the benzene ring and the carboxylate group. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxylate O atoms of the anion via a pair of N—H⋯O hydrogen bonds with an R 2 2(8) ring motif, forming an approximately planar ion pair with a dihedral angle of 9.63 (4)° between the pyridinium and benzene rings. The ion pairs are further connected via N—H⋯O and weak C—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the bc plane.

The 4-methylbenzoate anion of the title salt, C 6 H 9 N 2 + Á-C 8 H 7 O 2 À , is nearly planar, with a dihedral angle of 6.26 (10) between the benzene ring and the carboxylate group. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxylate O atoms of the anion via a pair of N-HÁ Á ÁO hydrogen bonds with an R 2 2 (8) ring motif, forming an approximately planar ion pair with a dihedral angle of 9.63 (4) between the pyridinium and benzene rings. The ion pairs are further connected via N-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds, forming a twodimensional network parallel to the bc plane.

Experimental
Hot methanol solutions (20 ml) of 2-amino5-methylpyridine (54 mg, Aldrich) and 4-methylbenzoic acid (34 mg, Merck) were mixed and warmed over a heating magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly at room temperature and crystals of the title compound (I) appeared after a few days. were refined using a riding model, with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). A rotating group model was used for the methyl group.

Figure 1
The molecular structure of the title compound with atom labels with 50% probability displacement ellipsoids.

Figure 2
A crystal packing diagram of the title compound. H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity.

2-Amino-5-methylpyridinium 4-methylbenzoate
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.