| 17004289 |
Rey S, Davies DM: Photochemistry of peroxoborates: borate inhibition of the photodecomposition of hydrogen peroxide. Chemistry. 2006 Dec 13;12(36):9284-8.
The UV absorbance and photochemical decomposition kinetics of hydrogen peroxide in borate/boric acid buffers were investigated as a function of pH, total peroxide concentration, and total boron concentration. At higher pH borate/boric acid inhibits the photodecomposition of hydrogen peroxide (molar absorptivity and quantum yield of H (2) O (2) and HO (2) (-), (19.0+/-0.3) M (-1) cm (-1) and 1, and (237+/-7) M (-1) cm (-1) and 0.8+/-0.1, respectively). The results are consistent with the equilibrium formation of the anions monoperoxoborate, K (BOOH)=[H (+)][HOOB (OH)(3) (-)]/([B (OH)(3)][H (2) O (2)]), 2.0 x 10 (-8), R. Pizer, C. Tihal, Inorg. Chem. 1987, 26, 3639-3642, and monoperoxodiborate, K (BOOB)=[BOOB (2-)]/([B (OH)(4) (-)][HOOB (OH)(3) (-)]), 1.0+/-0.3 or 4.3+/-0.9, depending upon the conditions, with molar absorptivity, (19+/-1) M (-1) cm (-1) and (86+/-15) M (-1) cm (-1), respectively, and respective quantum yields, 1.1+/-0.1 and 0.04+/-0.04. The low quantum yield of monoperoxodiborate is discussed in terms of the slower diffusion apart of incipient (.) OB (OH)(3) (-) radicals than may be possible for (.) OH radicals, or a possible oxygen-bridged cyclic structure of the monoperoxodiborate. |
81(1,1,1,1) |