Hydrogen peroxide photochemistry

Dilling, W.L., Gonsior, S.J., Boggs, G.U., Mendoza, C.G. (1988) Organic photochemistry. 20. A method for estimating gas-phase rate for reactions of hydroxyl radicals with organic compounds from their relative rates of reaction with hydrogen peroxide under photolysis in 1,1,2-trichlorotrifluoroethane solution. Environ. Sci. Technol. 22, 1447-1453. 

Two additional systems were exploited in order to confirm the involvement of free-radical processes during vindoline oxidations. These were the enzyme peroxidase and photochemistry. Horseradish peroxidase (HRP) oxidized both vindoline and 16-O-acetylvindoline in the presence of hydrogen peroxide. Vindoline was converted to the enamine dimer 59 (78). During the reaction, the following sequence of redox reactions occurs ... 

Ortmans I, Moucheron C, Kirsch-De Mesmaeker A (1998) Ru(ll) polypyridine complexes with a high oxidation power. Comparison between their photoelectrochemisty with transparent SnC>2 and their photochemistry with desoxyribonucleic acids. Coord Chem Rev 168 233-271 Ozawa T, Ueda J, Flanaki A (1993) Copper(ll)-albumin complex can activate hydrogen peroxide in the presence of biological reductants first ESR evidence for the formation of hydroxyl radical. Biochem Mol Biol Int 29 247-253... 

Xenopoulos, M. A., and D. F. Bird. 1997. Effect of acute exposure to hydrogen peroxide on the production of phytoplankton and bacterioplankton in a mesohumic lake. Photochemistry and Photobiology 66 471 178. 

Nitrate photolysis is a relevant source of hydroxyl in natural waters. A study carried out on the Greifensee Lake water indicates that nitrate photolysis is a much more important source of hydroxyl when compared with the photolysis of hydrogen peroxide or the Fenton reaction [12]. Nitrate photochemistry can thus lead to a steady-state hydroxyl concentration around 5 x 10 16 M [8]. 

We focus initially on the photochemical behaviour of complexes of Fe(III) with simple carboxylic acids and give particular attention to oxalic acid. This compound is prevalent in atmospheric aerosols [28], provides a simple example of environmentally important light-mediated ligand-to-metal charge transfer (LMCT) processes which result in ligand decarboxylation [27] and is used to initiate the degradation of contaminants both in the absence and presence of added hydrogen peroxide (via the so-called modified photo-Fenton process [29,30]). In addition, the photochemistry of Fe(III)-oxalate complexes has been studied in detail, as it is the basis of... 

Other reactive species are or may be formed upon irradiation of CDOM, but their production rates were determined (or are considered) to be much lower than for the species represented in Scheme 1. Nevertheless, these species can be important for the transformation of organic contaminants that are not susceptible to reaction with the main reactive species. They comprise the hydroxyl radical, the carbonate radical and all the radicals derived from the DOM (carbon-centred, oxyl, peroxyl radicals). The following subsections describe in more detail the role that each reactive species plays in the transformation of aquatic organic contaminants. Hydrogen peroxide, although considered a reactive oxygen species (ROS) and an important player in aquatic photochemistry [7], is neglected because there is no evidence that... 

Fig. 6.12 Comparison of photochemistry and quantum yields of hydrogen peroxide and of ozone gas phase photochemistry of O3 see text.

Another feature of interest is related to the quantum yields of hydrogen peroxide and of ozone photochemistry as is outlined in Fig. 6-12. Theoretically, the photolysis of 1 mol of H2O2 should produce 2 mol of hydroxyl radicals with a calculated maximum quantum yield of two, according to the definition of presented in Tab. 3-7 = However, the experimental situation is much... 

This section has called attention to some ways that vertical mixing complicates the photochemistry of natural waters. On the other hand, if the rates of CDOM absorption and photochemistry can be quantified, then the steady state profile of a photochemical product (i.e. dissolved hydrogen peroxide) can be used to infer vertical mixing rates. This was possible in freshwater systems (Canadian Lakes and the St. Lawrence River) that accumulate higher levels of peroxide due to their CDOM content [36,46]. A similar attempt to model the depth-time variation of hydrogen peroxide in the ocean (where CDOM is much lower) was only partially successful in reproducing the observed distribution [47,48]. 

D.R.S. Lean, W.J. Cooper, F.R. Pick (1994). Hydrogen peroxide formation and decay in lake waters. In G.R. Helz, R.G. Zepp, D.G. Crosby (Eds), Aquatic and Surface Photochemistry pp.201-214). CRC Press, Inc, Boca Raton. 

R.G. Zepp, Y.I. Skurlatov, J.T. Pierce (1987). Algal-induced decay and formation of hydrogen peroxide in water Its possible role in the oxidation of anilines by algae. In R.G. Zika, W.J. Cooper (Eds), Photochemistry of Environmental Aquatic Systems... 

A Wojciak, M Sikorski, R Gonzalez Moreno, JL Bourdelande, and F Wilkinson. The Use of Diffuse-Reflectance Laser-Flash Photoysis to Study the Photochemistry of the Kraft Pulp Treated with Hydrogen Peroxide under Alkaline and Acidic Conditions. WoodSci. Technol. 36 187-195, 2002. 

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