Organic peroxy radical

Organic peroxy radicals ROO Photolysis of dissolved organic material... 

The OH radical also reacts with non methane hydrocarbons (NMHCs) producing a variety of organic peroxy radicals (R02). H02 and CH302 react with NO producing OH and CH30, respectively (Reactions 5, 6). 

Primary organic peroxy radical R02 Methylglyoxal (CH3C(0)C(0)H) MGLY... 

Secondary organic peroxy radical R02R Peroxide radical of MGLY (CH3C(0)C(0)00) MGPX... 

Nitrated organic peroxy radical PN02 Methacrolein OH-adduct MAC1... 

If oxygen is present, organic peroxy radicals ROO° can be formed. These can further react, eliminating 02°7H02° and so enter again into the chain reaction. 

The H atoms formed in reaction 15a can react with 02 (reaction 11) to form H02. The stabilized Criegee intermediate (CH200) can participate in further reactions, some of which will result in the formation of peroxy radicals. Larger alkenes react with ozone to produce organic peroxy radicals. 

Figure 1. Hydroperoxy and organic peroxy radical concentrations as simulated for the marine boundary layer with (solid line) and without (dotted line) peroxy radical permutation reactions. (Reproduced with permission from reference 22. Copyright 1990 American Geophysical Union.)...

The analysis of the spectrum is a multiple-step process. The first step is the removal of the contribution to the spectrum due to the sampling apparatus. The next step is subtraction of the relatively large contribution due to N02. The remaining absorptions are due to H02, other organic peroxy radicals, and possibly other unknown radicals. A numerical fitting procedure... 

This chain reaction converts NO and CO to N02 and CO at a rate proportional to the sum of the H02 and HO concentrations. The technique also measures certain organic peroxy radicals, because they are converted to H02 after a few steps. Peroxy radicals are converted to H02 according to the following reactions for primary peroxy radicals ... 

In the presence of oxygen, the organic radical (R) reacts with oxygen to form an organic peroxy radical (ROO ) ... 

The organic peroxy radical abstracts a hydrogen atom from the organic compound, producing an organic hydroperoxide (ROOH) and another organic radical ... 

Hendry, D.G. and D. Schuetzle. 1976. Reactions of hydroperoxy radicals. Comparison of reactivity with organic peroxy radicals. ]. Org. Chem. 41 3179-3182. 

Another potential dark source of in the atmosphere, more particularly in the boundary layer, is from the reactions between ozone and alkenes. The ozonolysis of alkenes can lead to the direct production of the OH radical at varying yields (between 7 and 100%) depending on the structure of the alkene, normally accompanied by the co-production of an (organic) peroxy radical. As compared to both the reactions of OH and NO3 with alkenes the initial rate of the reaction of ozone with an alkene is relatively slow, this can be olfset under regimes where there are high concentrations of alkenes and/or ozone. For example, under typical rural conditions the atmospheric lifetimes for the reaction of ethene with OH, O3 and NO3 are 20 h, 9.7 days and 5.2 months, respectively in contrast, for the same reactants with 2-methyl-2-butene the atmospheric lifetimes are 2.0 h, 0.9 h and 0.09 h. 

Therefore, it would seem that this product is formed through an organic-peroxy radical as intermediate, rather than through the reaction of a malic acid radical as required hy the basic mechanism. 

Organic peroxy radicals Polar oxidation products of organic compounds ROO Photolysis of dissolved organic material Photochemical oxidation of dissolved or adsorbed organic material... 

Compounds that are classified as antioxidants (such as alkylphenols, aromatic amines, thiophenols, and imines) generally exhibit moderately high reactivity toward organic peroxy radicals (ROO ). A plausible reaction sequence for the formation of ROO is given in Figure 12.3b. 

The intermediates formed in AOPs sometimes are more toxic than the parent compounds and are required to be decomposed completely using either combination of AOPs or combination of AOP and some other treatment methods such as adsorption and biodegradation. Carbonyl compounds, particularly aldehydes, are quite toxic, and some of the secondary compounds formed from aldehydes, especially peroxyacylnitrates are more dangerous than the parent compounds. Organic peroxy radical (ROj) reactions are of significance because they represent an important class of intermediates formed in the oxidation process of hydrocarbons (15). Intermediates such as ethers and alcohols have enhanced reactivity toward hydroxyl radical. The rate constant of oxidation of these compounds is of similar order of magnitude as of the alkanes. 

Organic Peroxy Radical Concentration as an Environmental Factor... 

For measuring the steady-state concentration of organic peroxy radicals (ROO ) produced in sunlit natural waters series of antioxidants, such as poly-methylphenols, have been successfully applied as selective probe compounds (Faust and Hoigne, 1987). The rates of transformation have shown that the steady-state concentration of the apparent photooxidants increases with the amount of light absorbed by the DOM. The sink for ROO has not been identified, but kinetic evidence is that DOM, even when the DOC amounts up to 5 mgL"1, does not control the lifetime of the peroxy radicals. The following reaction scheme summarizes the results of the kinetic analysis for peroxy radical formation ... 

The methylperoxy radical can react with NO, N02, HOz radicals, and itself (also other organic peroxy radicals R02 ). The reaction with NO, analogous to reaction (6) (and 19),... 

The organic peroxy radicals (R-22) can also undergo a variety of unimolecular reactions [Ingold, 1969 Dole, 1973b] the most relevant of these is the chain scission leading to the formation of carbonyl and hydroxy compounds ... 

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