Química Nova (Jan 2006)
Fotoquímica de alfa,alfa-dimetilvalerofenona adsorvida em celulose microcristalina
Abstract
Irradiation of a,a-dimethylvalerophenone (1) adsorbed on microcrystalline cellulose employing methanol as the solvent shows a Norrish Type II/Type I ratio of 1.0?0.1. In solution, values of 2.3?0.3 in benzene and 8.7?2.0 in terc-butanol were obtained. The cyclization/elimination ratio for the Norrish Type II reaction of 1 shows values of 1.2?0.3 in cellulose, 17.9?2.7 in benzene and 3.2?03 in terc-butanol. When samples of 1/microcrystalline cellulose were prepared employing n-hexane, the Type II/Type I (29.5?2.9) and the cycl/elim (113.3?12.1) ratios were dramatically modified. These results demonstrate the difference in the behavior of 1 when entrapped in the cellulose chains or adsorbed on the cellulose surface.
