Hydrogen-bonded complexes of 2-pyridone with centrosymmetric and non-centrosymmetric dicarboxylic acids

2-Pyridone (2-oxopyrimidine) forms hydrogen-bonded complexes with dicarboxy lic acids, the molar ratio of 2-pyridone/di carboxylic acid being 2:1 for t he complexes with oxalic acid (ethanedioic acid), 2C(5)H(5)NO .C2H2O4, (I), and trans-beta -hydromuconic acid (trans-hex-3-enedioic acid), 2C(5)H(5)NO .C6H8O4, (II), and 1:1 for the complexes with trans-glutaconic acid (trans -pent-2-enedioic acid), C5H5NO . .C5H6O4, (III), and L-tartaric acid (L-2,3 - dihydroxybutanedioic acid), C5H5NO .C4H6O6.H2O, (IV). Common features in the hydrogen-bonding patterns were found for the centrosymmetric and non-ce ntrosymmetric acids, respectively. The 2-pyridone molecule takes the lactam form in these crystals.