SOLUTION PHOTOCHEMISTRY OF AZULENE

Photochemical reactivity has been observed in solution-phase azulene. Experiments are described which confirm photoinduced deuteration, chlorination, and polymerization. The threshold for the observed chemistry is at the origin of S-2 which is at 27956 +/- 8 cm(-1) (357.7 +/- 0.1 nm) in chloroform. Only one photon is required to induce the observed chlorine substitution reactions. Although no naphthalene is formed, this chemical channel appears to be the equivalent of a thermal reaction, with the substitutions taking place at the two equivalent positions: on the small ring of azulene. The mechanism of these reactions is bimolecular in nature. Chlorination provides a complex mixture of products in most cases; however, deuteration proceeds cleanly giving only 1,3-d(2)-azulene.