Solution Spectra and Oscillator Strengths of Electronic Transitions of Pyridine and Some Monosubstituted Derivatives

The near ultraviolet absorption spectra of the following substances have been measured in iso-octane and ethyl alcohol solutions: pyridine, the isomeric picolines, 2- and 3-fluoropyridine, 2- and 3-chloropyridine, and 2- and 3-bromopyridine. Solvent effects were observed and oscillator strengths were measured for the singlet-singlet π—π* and n—π* electronic transitions which occur in the spectral region 34 000 cm-1 to 48 000 cm-1. It was found that in this spectral region the n—π* transition is missing in the case of 2-fluoro-, 2-chloro- and 2-bromopyridine.