Molecular Structure, Vibracional Spectra and Photochemistry of Picolinamide, Nicotinamide and Isonicotinamide in Solid Matrices

ANA BORBA, ANDREA GÓMEZ-ZAVAGLIA, RUI FAUSTO

Turín, Italia

Congreso; 41st IUPAC World Chemistry Congress. Chemistry Protecting Health, Natural Environment and Cultural Heritage.; 2007

IUPAC

3 isomers of pyridinecarboxamide: picolinamide (PA), nicotinamide (NA) and isonicotinamide (INA), show important biological activity[1]. In order to compare the effect of the N heterocycle position on the structure and photochemical reactivity of the carboxamide moiety, NA, PA and INA have been investigated by matrix isolation FTIR spectroscopy and quantum chemical methods. According to calculations, 2 conformers were predicted for PA and NA and 1 for INA. In consonance with the theoretical results (DE=2.97 kJ mol-1 at the MP2/6-311++G(d,p) level), the matrix isolation experiments confirmed the presence of both conformers (E and Z) in the matrix. In contrast, for PA only E-conformer was observed experimentally, in agreement with theoretical calculations (DE=37.1 kJ mol-1). UV irradiation of PA and NA, pyridine and isocyanic acid were produced in the matrices, indicating that the photocleavage of the C(=O)−C bond, followed by H migration from the amide group to the heterocyclic ring. Isocyanic acid further reacts to yield CO+NH. Irradiation of INA did not lead to any observable photoreaction, showing its the greater photostability.