Radical radiolytic generation

Accordingly, the exterior surface is much more reactive than planar analogues, and is comparable to those of electron deficient polyolefins. This, in turn, rationalizes the high reactivity of the fullerene core towards photolytically and radiolytically generated carbon- and heteroatomic-centred radicals and also other neutral or ionic species [8]. The interior, in contrast, is shown to be practically inert [9]. Despite these surface related effects, the... 

Attack of the OH radical on carbohydrates of low molecular mass gives rise to a variety of products. Indeed, the reaction of radiolytically-generated OH radical with lower hexose sugars produces lower saccharides (for di- and higher saccharide species), uronic and aldonic acids, and 3-, 2- and 1-carbon aldehydic fragments, e.g. 

Grootveld et al. (1994) employed this technique to investigate radiolytic, damage to biomolecules present in human body fluids. 7-Radiolysis of healthy or rheumatoid human serum (5.00 kGy) in the presence of atmospheric O2 gave rise to reproducible elevations in the concentration of NMR-detectable acetate, which are predominantly ascribable to the prior oxidation of lactate to pyruvate by OH radical followed by oxidative decarboxylation of pyruvate by radiolytically generated H2O2 and/or further OH radicals (Equations 1.7 and 1.8). 

In addition to causing DNA strand breaks, tirapazamine damages the heterocyclic base residues of double-stranded DNA.2 " 2 Similar to authentic, radiolytically generated hydroxyl radical, the drug causes approximately four times more base... 

Hydroxyl radicals were generated radiolytically in NaO-saturated aqueous solutions of thiourea and tetramethylthiourea. Conductometric detection showed that HO and a dimeric radical cation were produced. The dimeric radical cation is formed by addition of a primary radical to a molecule of thiourea. In basic solution, the dimeric radical cation decays rapidly to a dimeric radical anion, which is formed via neutralization of the cation and subsequent deprotonation of the neutral dimeric radical (Scheme 16). This was not observed in tetramethylurea. These dimeric radical cations of thiourea and tetramethylurea are strong oxidants and readily oxidize the superoxide radical, phenolate ion, and azide ion. 

Carbon dioxide itself can accept e. during radiolysis of water, giving rise to the carbon dioxide anion-radical. This anion-radical can add to carboradicals. Thus, aliphatic alcohols react with the radiolytically generated hydroxyl radicals, rupturing their C—H bonds RCHjOH + OH HjO + RCH OH. These radicals accept the radiolytically generated COj" forming a-hydroxycarboxylic acids RCHjOH + CO2 RCH(OH)COO (Morkovnik and Okhlobystin 1979). 

In experiments where ion-radicals are generated by radiolytic reduction or oxidation in solid matrices, the concentration of solute molecules must be at least 10 M to ensure efficient scavenging of the initially generated electrons or holes. At the same time, the upper limit of the solute concentration should not exceed 10 -10 M. It is necessary that the direct effect of radiation on the solute molecule should be ignored. This is one of the major requirements for successful use of radiolytic methods for generating ion-radicals. 

Understandably, most workers who use radiolysis, photoionization, CTFS, or CTTS as the means for generation of (secondary) radical ions pay little attention to the nature of short-lived precursors of these ions. After all, the subject of interest is a secondary rather than a primary ion. This ad hoc approach is justifiable because radiolytic production is just another means of obtaining a sufficient yield of the radical ion. Quite often in such studies, the radiolysis is complemented by other techniques for radical ion generation, such as plasma oxidation, electron bombardment-matrix deposition, and chemical and electrochemical reduction or oxidation. While the data obtained in these studies are useful, there is little radiation chemistry in such—nominally, radiation chemistry—studies. 

There are many excellent books and reviews on the structure and reactions of secondary radical ions generated in radiolytic and photolytic reactions. Common topics include the means and kinetics of radical ion production, techniques for matrix stabilization, electronic and atomic structure, ion-molecule reactions, structural rearrangements, etc. On the other hand, the studies of primary radical ions, viz. solvent radical ions, have not been reviewed in a systematic fashion. In this chapter, we attempt to close this gap. To this end, we will concentrate on a few better-characterized systems. (There have been many scattered pulse radiolysis studies of organic solvents most of these studies are inconclusive as to the nature of the primary species.)... 

D Angelantonio, M., M. Venturi, and Q. G. Mulazzani, A Reexamination of the Decay Kinetics of Pulse Radiolytically Generated Br2 Radicals in Aqueous Solution, Radial. Phys. Chem., 32, 319-324 (1988). 

Charge alteration on the surfaces of nanosized metallic silver particles has been investigated by simultaneously monitoring absorption and conductivity changes during pulse-radiolytic experiments [506]. Pulse radiolysis of a nitrous-oxide-(N20) saturated aqueous solution of 3.0 nm diameter metallic silver particles containing 0.2 M 2-propanol resulted in electron injection to the colloid. NzO functions to double the yield of hydroxyl radicals ( OH) generated in water... 

Most free-radical reactions of synthetic value are chain reactions, the key steps of which are illustrated in Scheme 4.1. In the initiation step, a reactive radical is generated from a nonradical precursor (initiator). In many cases, this can be accomplished thermally. For instance, peroxides possess a weak oxygen-oxygen bond and, consequently, undergo homolytic dissociation upon heating ROOR —> 2RO . Free radicals can also be generated photochemically, radiolytically, or by electron transfer from appropriate precursors. 

Cyclam)Ni(II) complexes react readily with methyl radicals [12]. The resulting (cyclam)Ni(III)-CH3 intermediates transform with excess radiolytically generated methyl radicals to ethane and reform the initial Ni(II) complex. The kinetics was determined. 

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