Radicals, formation during radiolysi

Radical chain processes 772, 1063 Radical clock 1059 Radical reactions radical-molecule 1102-1111 radical-radical 1099-1102 unimolecular 1098, 1099 Radicals, formation during radiolysis 891-922... 

Since the overall reaction proceeds under conditions where no Co(CO)4 radicals from Co2(CO)g cleavage can be detected, splitting of the dinuclear species Co2(CO)gL, which is formed in a rapid preequilibrium (equation 4), is responsible for radical formation during the induction period. The important step for the formation of the observed products is then outer-sphere electron transfer see Outer-sphere Reaction) as depicted in equation (6). This requires the Co(CO)3L radical to act as a reducing agent towards Co2(CO)g. Since, from electrochemistry and pulse radiolysis of Co2(CO)g, it can... 

Amino acids, sulphoxide, radiolysis of 909 a-Amino acids, reactions of 776, 777 a-Aminosulphones, synthesis of 176 Aminosulphonyl radicals 1093 Aminosulphoxides rearrangement of 740 synthesis of 336 Andersen synthesis 60 / -Anilinosulphoxides, synthesis of 334, 335 Anion radicals 1048-1050 ESR spectra of 1050-1054 formation of during electrolysis 963 during radiolysis 892-897, 899, 903 Annulation 778, 781, 801, 802 Antibiotics, synthesis of 310 Arenesulphenamides 740 Arenesulphenates 623 reactions of 282 rearrangement of 719 Arenesulphinates 824, 959 chiral 618... 

In 1972, Miller made a detailed analysis of the data on the influence of electron acceptor additives on the yield of ionic products during radiolysis of organic matrices and showed this to agree quantitatively with the electron tunneling mechanism of the formation and annihilation of these particles [7], In particular, the annihilation of et) in MTHF glass containing naphthalene (Nh) as the additive was found to be accompanied by simultaneous formation of the Nh anion radical (via the reaction etj. + Nh - Nh ). The kinetic curves for this reaction at 77 and 87 K coincided, which ruled out the possibility of the reaction rate being determined by thermal diffusion. 

The formation of trapped electrons during radiolysis of vitreous water-alkaline matrices is known to be accompanied by the formation of O anion radicals which serve as acceptors for etr [27]. The trap for the O anion radicals in these matrices, suggested in ref. 36, is represented schematically in Fig. 10. When water alkaline matrices irradiated at 77 K are heated to T 150 K, i.e. to a temperature at which glass softening starts, the concentrations of et" and O decrease simultaneously [37]. This appears to be related to the occurrence of a reaction between them... 

Dor the correct interpretation of the phenomena taking place in the radiolysis of sulfuric acid solutions, a good understanding of the radiolytic behavior of the peroxysulfuric acids, as well as of the ultimate fate of the sulfate radicals is necessary. In fact, the peroxyacids of sulfuric acid are formed during radiolysis with yields which depend on the H2S04 concentration (I, 4). In aerated solutions this peroxyacid formation has been considered as the net result of Reactions 1 to 5 ... 

Alkyl and acyloxy radicals are formed during radiolysis of acyl hpids. These will further react to form volatile compounds. The formation of alkanes and alkenes, that lack one or two C-atoms, from the original acyl residue are of interest for the detection of irradiation (Fig. 3.39). 

This review is concerned with the formation of cation radicals and anion radicals from sulfoxides and sulfones. First the clear-cut evidence for this formation is summarized (ESR spectroscopy, pulse radiolysis in particular) followed by a discussion of the mechanisms of reactions with chemical oxidants and reductants in which such intermediates are proposed. In this section, the reactions of a-sulfonyl and oc-sulfinyl carbanions in which the electron transfer process has been proposed are also dealt with. The last section describes photochemical reactions involving anion and cation radicals of sulfoxides and sulfones. The electrochemistry of this class of compounds is covered in the chapter written by Simonet1 and is not discussed here some electrochemical data will however be used during the discussion of mechanisms (some reduction potential values are given in Table 1). 

Apart from the relevance to the radiation-induced polymerizations, the pulse radiolysis of the solutions of styrene and a-methylstyrene in MTHF or tetrahy-drofuran (THF) has provided useful information about anionic polymerization in general [33]. Anionic polymerizations initiated by alkali-metal reduction or electron transfer reactions involve the initial formation of radical anions followed by their dimerization, giving rise to two centers for chain growth by monomer addition [34]. In the pulse radiolysis of styrene or a-methylstyrene (MS), however, the rapid recombination reaction of the anion with a counterion necessarily formed during the radiolysis makes it difficult to observe the dimerization process directly. Langan et al. used the solutions containing either sodium or lithium tetrahydridoaluminiumate (NAH or LAH) in which the anions formed stable ion-pairs with the alkali-metal cations whereby the radical anions produced by pulse radiolysis could be prevented from rapid recombination reaction [33],... 

Radiopharmaceuticals comprising /J-emitting radionuclides may undergo autoradiolysis during preparation and storage. Radiolysis is caused by the formation of free radicals such as hydroxyl and superoxide radicals [98], and is de-... 

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