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Photochemistry of Peroxoborates: Borate Inhibition of the Photodecomposition of Hydrogen Peroxide
Author(s) -
Rey Sébastien,
Davies D. Martin
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600437
Subject(s) - hydrogen peroxide , chemistry , boric acid , molar absorptivity , quantum yield , radical , absorbance , boron , yield (engineering) , photochemistry , decomposition , peroxide , molar ratio , nuclear chemistry , inorganic chemistry , fluorescence , catalysis , organic chemistry , materials science , chromatography , quantum mechanics , physics , optics , metallurgy
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 ]), 2.0×10 −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.