COCRYSTALLINE SALTS OF ALKYNOIC ACIDS - THE CRYSTAL AND MOLECULAR-STRUCTURE OF 2-AMINOPYRIDINIUM BUTYNOATE

Mixing 2-butynoic acid and 2-aminopyridine in acetone produces the sal t 2-aminopyridinium 2-butynoate (4) in high yield. An X-ray structure determination of 4 (Space Group P2(1)/n, Z = 4) shows it to contain sh ort acetylene-acetylene contacts as well as short contacts between the pyridine N atom and the beta-carbon atom of the butynoate moiety. The contacts are between centrosymmetrically-related ''dimer pairs'' of t he cocrystalline salt, and are not part of an infinite array. The mate rial is stable to heating or exposure to Co-60 gamma-rays.