Hydroxyl radical addition

In addition, phenols are formed by the reaction of hydroxyl radical addition to the aromatic ring of oxidized alkylaromatic hydrocarbon [56]. 

J. Llano et al., Mechanism of hydroxyl radical addition to imidazole and subsequent water elimination. J. Phys. Chem. B 103, 5598-5607 (1999)... 

For the reaction of hydroxyl radical with organic species, there are three common reaction pathways (a) hydroxyl radical addition to unsaturated systems (e.g., double bonds), (b) hydrogen abstraction (typically from alkyl or hydroxyl groups), and (c) direct electron transfer. These generic mechanisms are illustrated in Figure 1. For nonradical reactants, all three mechanisms result in initial products that are radicals. Subsequent reactions follow to yield nonradical products. Additional reactants are necessary to complete these subsequent reactions. Common reactants include Fe2+, Fe3+, 02, H20, H+, HO, other metals, other organics, and other radicals present in the system. Dimerization can also occur if the initially formed radical species reacts with... 

Experimental investigations of adenine and guanine monohydrate crystals also indicate that products formed through net hydroxyl radical addition may also be formed in these crystals. For example, early ESR studies on frozen aqueous solutions of deoxyadenosine 5 -monophosphate [37] revealed one isotropic coupling (29 G) which was believed to be due to a radical formed through addition of a hydroxyl radical to C8 in adenine [A(C80H)]. The calculated results for the C8-hydroxylated radical (28.8 G) indicate that this coupling is... 

The examples of hydroxyl radical addition products identified in single crystals of adenine and guanine base derivatives confirm that water can play an important role in the radiation damage mechanism. It should be noted that the new mechanism has attracted some criticism [38]. The main objection is that nonplanar geometries were calculated for the gas phase radicals whereas planar structures are expected experimentally due to the hydrogen-bonding scheme... 

The most reliable data for hydroxyl radical additions to double and triple bonds have been collected in Table 41. It should be noted that, while no competition studies seem to have been made, the reactivity of... 

Formation of phenol very likely requires an ipso addition of C02 to chlorobenzene, as shown in reaction (R35). The ipso position was also reported to be the preferred site for hydroxyl radical addition to chlorobenzene." The bimolecular reaction of the ipso adduct C02 CHD with HO-CHD radicals of chlorobenzene is an alternative reaction channel yielding benzoic acid, HCI and chlorophenol, reaction (R36). Elimination of HC02 from the ipso adduct, reaction (R37), and subsequent reaction with HO-CHD radicals leads to the formation of phenol, HCI and chlorophenol," reaction (R38). 

Hydroxyl radical addition to bases such as guanine, proceeds very rapidly and leads to the formation of 8-hydroxydesoxyguanosine, which is used as a fingerprint of nucleobase oxidative damage. 

Previous studies have indicated that MP2 is able to successfully describe reaction profiles of the hydroxyl radical addition and abstraction reactions [20-26], albeit the high level of spin contamination in the UHF wave functions have shown the use of projection techniques to be essential. Very few previous studies have been reported, in which density functional methods have been employed for these types of reactions. The current review is based on work conducted in our research groups during the last 2 years [27-30]. 

Hydroxyl radical addition to the purine bases can in principle occur at Cl, C4, C5 and C8 (cf Fig. 1). Of these, addition to position C4, C5 and C8 in guanine and adenine are known to result in ring opening, ring saturation, or hydroxylation [15]. The most well-characterized purine radicals in irradiated DNA are 8-hydroxy-... 

We have in the present chapter tried to outline a series of theoretical investigations performed at the B3LYP, HF and MP2 levels, of hydroxyl radical addition reactions to systems of biological relevance. Unveiling the fundamental interactions for these types of systems may assist in gaining a deeper understanding of the mechanisms... 

Sulfuranyls with two alkyl groups produced either through reduction of sulfoxides [90, 91] or hydroxyl radical addition to sulfides [92] are typically too unsta-... 

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