Photochemical Processes due to n-π* and π-π* Transitions of 2-Picoline N-Oxide in the Vapor Phase

The gaseous photolysis of 2-picoline N-oxide was carried out by irradiation with the 3261Å (Cd 3P1) or 2537Å (Hg 3P1) resonance lines corresponding to an n-π* or a π-π* absorption of this substance, respectively. In the case of 3261Å irradiation, the major product was 2-pyridinemethanol, whose quantum yield showed a marked temperature-dependence. The activation energy necessary for the production of 2-pyridinemethanol was estimated to be about 3.4 kcal. mol−1. On the other hand, the photolytic products at 2537 Å irradiation were 2-picoline and other decomposition products and polymers. The quantum yield of 2-picoline showed a marked temperature-dependence, which may be attributed to the interaction between the 2-methyl group and the N→O group. The activation energy necessary for the production of 2-picoline was estimated to be about 1.1 kcal. mol−1.