A BLUE CHEMILUMINESCENCE IN THE REACTION OF UMBELLIFERONE WITH HYPOCHLORITE

A strongly fluorescing 7-hydroxycoumarin (umbelliferone, U) oxidized in dilute (10 mu mol/L-0, 1 mol/L) aqueous solution with ClO- or ClO- + H2O2 (but not with H2O2 alone) produces a strong chemiluminescence (CL). Light emission kinetics depends on the pH of solution (4.0-10.5) and the reaction has a low activation energy E(a) = 31 +/- 2 kJ/mol (285-310 K). The spectrum covers the fluorescence of umbelliferone (400-550 nm, lambda(max) 460 nm). No red emission typical of 1 Delta g, 1 Sigma(+)g (O-2)(2) is observed either in the umbelliferone +ClO- or the umbelliferone +ClO- + H2O2 solution. The possible mechanism of CL and concomitant degradative oxidation of umbelliferone is discussed.