Electronic absorption spectra of some nicotinamides and nicotinic acids. Molecular orbital treatment

✍ Scribed by R. H. Abu Eittah; M. M. Hamed; A. A. Mohamed

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 401 KB
• Volume: 64
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1997)64:6<689::aid-qua6>3.0.co;2-s

✦ Synopsis

The electronic absorption spectra of the position isomers nicotinamide and isonicotinamide, nicotinic acid, and isonicotinic acid were investigated, together with the spectra of thionicotinamide, N-methyl nicotinamide and nicotinic acid N oxide. Apparent differences in the spectra of the position isomers were interpreted in terms of the torsion angle between the planes of the molecule, the height of the barrier to internal Ž . rotation, and the results of molecular orbital MO calculations. The largest perturbation effect was observed in the case of thionicotinamide whereas the smallest effect was observed in the case of nicotinic acid N oxide. MO calculations have indicated the existence of overlapping transitions. The observed transitions proved to be -* transitions, none of the n-* was observed.