Hydroxyl radical reaction with bromide

PROBABLE FATE photolysis volatilized methyl bromide should photodissociate above the ocean layer, probably not significant in aquatic systems, reaction with photochemi-cally produced hydroxyl radicals has a half-life from 0.29-1.6 yrs, direct photolysis is the dominant fate in the stratosphere, but is not expected to be important in the troposphere oxidation atmospheric photooxidation by hydroxyl radicals releases inorganic bromide which is carried... 

Initially it was believed252 that hydroxyl radicals were the first formed products in these reactions but lack of any effect on the rate of the reaction by adding bromide, alcohols or benzene demonstrated that this was not the case. Furthermore, hydroxyl radicals react rapidly with [Ru(bipy)3]26 to give a complex with Amax = 750-800 nra which is similar to an intermediate in... 

For benzene hydroxylation an analytical system [37] was successfully used at the interface. This system contains Fe3+ hydrophobic complexes, which promote the process intensification. It is shown [38, 39] that compared with hydrophobic complexes, Fe3+ complexes with the phase transfer—tertiary ammonium salts and crown ethers—display more effective action. At 20-50 °C, owing to the use of trimethylacetylammonium bromide as the phase transferring agent, benzene is successfully hydroxylated in the two-phase water-benzene system in the presence of Fe3+ ions [40], Hence, it is Shilov s opinion [41] that in the case of cytochrome P-450 a radical reaction is probable. It produces radicals, which then transform in the cell, as follows ... 

However, hydroxyl radicals are very reactive and known to react with aromatic compounds not only by electron abstraction but also by adding to the ring. Well-established, one-electron oxidizing radicals such as Br2 and N3, formed by pulsing a nitrous oxide saturated solution of potassium bromide or sodium azide, are used to produce cation radicals of the drug molecules. For example, the reactions that take place when a nitrous oxide aqueous solution of lO2 M potassium bromide in the presence of 10 4 M chlorpromazine (C1P) is subjected to pulse radiolysis (Asmus et al., 1979 Davies et al., 1979) are given below ... 

PROBABLE FATE photolysis, could be important, only identifiable transformation process if released to air is reaction with hydroxyl radicals with an estimated half-life of 8.4 months oxidation, has a possibility of occurring, photooxidation half-life in air 42.7 days-1.2 yrs hydroiysis too slow to be important, first-order hydrolytic half-life 275 yrs voiatilization likely to be a significant transport process, if released to water or soil, volatilization will be the dominant environmental fate process, volatilization half-life from rivers and streams 43 min-16.6 days with a typical half-life being 46 hrs sorption adsorption onto activated carbon has been demonstrated bioiogicai processes moderate potential for bioaccumulation, biodegradation occurs in some organisms, in aquatic media where volatilization is not possible, anaerobic degradation may be the major removal process other reactions/interactions may be formed from haloform reaction after chlorination of water if sufficient bromide is present... 

Like heat and light stabilizers, flame retardants containing bromine or chlorine act as free-radical scavengers. They interrupt combustion essentially by replacing free hydrogen and hydroxyl radicals with halide (bromide or chloride) radicals that prevent the combustion reaction from continuing, according to a cyclic process (simplified here) ... 

Anticipated products from the reaction of ethylene dibromide with ozone or hydroxyl radicals in the atmosphere include bromoacetaldehyde, formaldehyde, bromoformalde-hyde and bromide radicals (Cupitt, 1980). In the atmosphere, ethylene dibromide is slowly oxidized by peroxides and ozone. The half-life for these reactions is generally >100 days (Leinster et al., 1978). 

The active alkoxyl radicals formed by this reaction start new chains. Apparently, the hydroperoxide group penetrates in the polar layer of the micelle and reacts with the bromide anion. The formed hydroxyl ion remains in the aqueous phase, and the MePhCHO radical diffuses into the hydrocarbon phase and reacts with ethylbenzene. The inverse emulsion of CTAB accelerates the decay of hydroperoxide MePhCHOOH. The decomposition of hydroperoxide occurs with the rate constant k = 7.2 x 1011 exp(-91.0/R7) L mol-1 s-1 (T = 323-353 K, CTAB, ethylbenzene [28]). The decay of hydroperoxide occurs more rapidly in an 02 atmosphere, than in an N2 atmosphere. 

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