Effect of solvents and a substituent group on photooxidation of fluorene

The effect of solvents and a substituent group on photooxidation of fluorene was investigated. Solutions of fluorene and its derivatives (c = 0.25 g l(-1)) were irradiated using artificial light from a xenon lamp (100 mW/cm(2)) and degradation (%), rate constants (k(p)), quantum yields (Phi) and half-lives (t(1/2)) were compared. In addition, reaction products formed in each case were analyzed and compared with those of fluorene. Photodegradation (%) for fluorene varied depending on the solvent used. Dichloromethane gave the largest rate constant (3.4 x 10(-4) s(-1)) and quantum yield (0.009). Both values decreased in the order of dichloromethane > acetonitrile > methanal > acetonitrile/water (70/30) > acetonitrile/water(50/50). The relation between the solubility of oxygen in solvent and the reactivity is described. 1-methylfluorene exhibited comparable photostability to that of fluorene, while 2-nitrofluorene showed good photostability. In case of 2-nitrofluorene, direct oxidation scarcely occurred and a replacement reaction was induced by the presence of a chlorine source. (C) 1998 Elsevier Science S.A. All rights reserved.