H2O2 and. Organic Peroxides

A triple complex is formed between V-(a-pyridyl)-2-thioquinaldamide (120), vanadate ions and H2O2 that becomes fluorescent in acidic solution (Aex = 340 nm, An = 490 nm). This reaction, originally developed for determination of V(V) in a FIA system, can be adapted for determination of H2O2 and organic peroxides. LOD for H2O2 is 0.05 p,M, with RSD 2.4% (ri = 3) at 1 p,M, with linearity in the 0.2 to 50 p,M range330. 

By contrast the epoxidation of olefins by H2O2 (and organic peroxides) which is catalyzed by TS-1 and TS-2 [80-83] is also catalyzed by other Ti containing solids including Ti-Al-Beta [84,85], Ti-MCM-41 [86] and mixed Ti02-Si02 oxides such as the ones described in [87,88]. 

Faust and co-workers have more recently examined the aqueous phase photochemical sources of peroxides (H2O2 and organic peroxides) in cloud waters at coastal sites [108-110]. Their research was directed towards answering several key questions [108] ... 

Kormann, C., D. W. Bahnemann, and M. R. Hoffmann. 1988. Photocatalytic production of H2O2 and organic peroxides in aqueous suspensions of TiOj, ZnO, and desert sand. Environ. Sci. Technol. 22, 798-806. 

If NO2 concentrations are low, the dominant termination reactions lead to the formation of hydrogen peroxide (H2O2) and organic peroxides (ROOH) ... 

Nitrogen and simultaneously formed non-organic (H2O2) and organic (ROOH) peroxides and peroxyacylnitrates are the strongest photo- and phyto oxidants. The increase of the concentration of these secondary pollutants in the atmosphere causes a decrease in bio-... 

The electrical wiring of redox enzymes entrapped in inorganic (e.g. sol-gel) matrices can also be achieved by the application of solution-state electron-relays that can penetrate through the matrix. For example, HRP films deposited in carbon paste substrates and then covered with a thin silica sol-gel layer have been used to detect H2O2 in aqueous media [55] and organic peroxides in nonaqueous solutions [56] by the use of [Fe(CN)6]" or ferrocene mediators, respectively. The extension of this electrode configuration to other enzymes has led to the development of new amperometric... 

An attempt has been made to rationalize oxygen transfer reactions from inorganic and organic peroxides. Alkaline H2O2 cleaves alkynes with the ratio of the rates of addition of HOJ and OH towards PhC=CC(0)Me being 1400. Two studies have been reported of the kinetics of the reaction of HO2 with methyl aryl sulfates in methanol which estimated the pKa for H2O2 in MeOH to be 15.8 0.2 at 298 K. 

For a review of reactions of H2O2 and metal ions with all kinds of organic compounds, including aromatic rings, see Sosnovsky, G. Rawlinson, D.J. in Swem Organic Peroxides, vol. 2 Wiley NY, 1970, p. 269. See also Sheldon, R.A. Kochi, J.K. Metal-Catalyzed Oxidations of Organic Compounds, Academic Press NY, 1981. 

MnP is the most commonly widespread of the class II peroxidases [72, 73], It catalyzes a PLC -dependent oxidation of Mn2+ to Mn3+. The catalytic cycle is initiated by binding of H2O2 or an organic peroxide to the native ferric enzyme and formation of an iron-peroxide complex the Mn3+ ions finally produced after subsequent electron transfers are stabilized via chelation with organic acids like oxalate, malonate, malate, tartrate or lactate [74], The chelates of Mn3+ with carboxylic acids cause one-electron oxidation of various substrates thus, chelates and carboxylic acids can react with each other to form alkyl radicals, which after several reactions result in the production of other radicals. These final radicals are the source of autocataly tic ally produced peroxides and are used by MnP in the absence of H2O2. The versatile oxidative capacity of MnP is apparently due to the chelated Mn3+ ions, which act as diffusible redox-mediator and attacking, non-specifically, phenolic compounds such as biopolymers, milled wood, humic substances and several xenobiotics [72, 75, 76]. 

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