The X-ray diffraction of molecular compounds of 2-aminopyridine with long chain saturated and unsaturated fatty acids

X-Ray diffraction measurements of long and short spacings are reported for the crystalline 1:1 and 4:1 molecular compounds of 2-aminopyridine with the C₁₀ to C₁₈ saturated fatty acids and the 1:1 and 2:1 compounds of oleic, elaidic, alpha-eleostearic and beta-eleostearic acids. Data are also reported for 2-aminopyridine, α-eleostearic acid and β-eleostearic acid. The angle of tilt of the 1:1 saturated compounds is 42°15′. The long spacings of the 4:1 compounds indicate a unit cell length of four molecules of fatty acid and one molecule of 2-aminopyridine with an angle of tilt of 62°15′. The contribution of the 2-aminopyridine to the length of a molecule of the 1:1 compounds is ca. 6 Å, the distance between the NH₂ and the CH₂ in the para position. In the 4:1 and 2:1 compounds it is ca. 3 Å, the distance between the NH₂ and the ring nitrogen.