W0355

Structural and Hydrogen Bonding Parameters for 3-(2-hydroxy-1-naphthylmethyleneamino) Benzoic acid (I) and 5-methyl-2-pyrazinecarboxylic acid (II). Allison J. Dobson, Dept. of Chemistry, Georgia Southern Univ., Statesboro, GA.

The title compound (I) crystallized in the centrosymmetric monoclinic space group P2₁/c with a, b, c, and $ equal to 11.644 (3), 7.458 (2)D, 16.257 (4), and 106.628 (6)E, respectively. The rings were planar as expected with a heavy atom maximum deviation from the least squares planes of 0.012(3)° for the naphthalene ring and 0.001(4)° for the benzene ring. The dihedral angle between the carboxyl group and the benzene ring was 4.50° resulting in an overall molecule that is very close to planar. An unusual characteristic of this molecule was that the O-H proton was transferred to N1 in the ring, thus producing an N-H---O intramolecular hydrogen bond. The other strong hydrogen bond, O1---O3, has a donor-acceptor distance of 2.628(4)D and an angle of 166.7. Two significant C-H---O interactions were also present. A monohydrate of 5-methyl-2-pyrazinecarboxylic acid (II) (MPCA), C₆N₂O₂H₆AH₂O, crystallized in the centrosymmetric space group C2/c with a, b, c, and $ equal to 11.550(7)D, 8.151(4)D, 16.29(1)D, and 105.29(1)E, respectively. The sample was crystallized from ethyl acetate by slow evaporation (colorless chunk). Crystals with a different appearance (colorless needles) were also obtained from the same growth. The needles, determined to be the anhydrous compound (structure previously determined), crystallized in the space group P2₁/c and compare favorably with the published structure. The hydrate exhibits some interesting hydrogen bonding patterns because of the water molecule.