Radical reactions radiolysis

In the case of diaryl sulfoxides the formation of both the aryl radical and the hydroxycyclohexadienyl radical was observed optically. Veltwisch and coworkers45 studied also the reaction of OH radicals from radiolysis of aqueous solutions of mixed (alkyl phenyl) sulfoxides (PhSOR). They found the formation of both alkylsulfinic and phenylsulfinic acids. 

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... 

In pulse radiolysis studies it is feasible to eliminate undesired radical reactions by the use of "scavengers". For example, to produce a totally reducing system simple aliphatic alcohols are added and the ensuing reaction... 

Ionic Reactions in TD/D2 Methane Mixtures. Previous investigation of the radiolysis of D2 containing small quantities of CH4 demonstrated that at low conversions all products anticipated from the H atom abstraction sequence except CH3D are absent from 125° to —196°C. and that the temperature coefficient of the rate of CH3D formation between 25° and 125 °C. is much too small for a purely atomic and free-radical reaction sequence (8). These observations are confirmed by new data presented in Table I. The new data also demonstrate the initial value of G(CH3D) is independent of temperature at 25°C. and below. 

Carotenoid radicals — Many of the important oxidations are free-radical reactions, so a consideration of the generation and properties of carotenoid radicals and of carbon-centered radicals derived from carotenoids by addition of other species is relevant. The carotenoid radicals are very short-lived species. Some information has been obtained about them by the application of radiation techniques, particularly pulse radiolysis. Carotenoid radicals can be generated in different ways. "... 

Adams, G.E. and Redpath, J.L. (1974). Selective free-radical reactions with proteins and enzymes pulse radiolysis and inactivation studies on papain. Int. J. Badiat. Biol. 25, 129-136. 

Debierne (1914) was the first to suggest a radical reaction theory for water radiolysis (H and OH). In various forms, the idea has been regenerated by Risse (1929), Weiss (1944), Burton (1947, 1950), Allen (1948), and others. Platzman (1953), however, criticized the radical model on theoretical grounds and proposed the formation of the hydrated electron. Stein (1952a, b) meanwhile had suggested that both electrons and H atoms may coexist in radiolyzed water and proposed a model in which the electron digs its own hole. Later, Weiss (1953, 1960) also favored electron hydration with ideas similar to those of Stein and Platzman. In some respects, the theoretical basis of these ideas is attributable to the polaron (Landau, 1933 Platzman and... 

Due to these reactions, hydrogen peroxide is an intermediate product of radiolysis of aerated water. Rate constants of free radical reactions with dioxygen and hydrogen peroxide are collected in Table 3.19. For the characteristics of solvated electron and information about its reactions, see monographs [219-223],... 

Pulse radiolysis is widely used for the study of fast free radical reactions and reactions of solvated electrons [223]. 

Advances in pulse radiolysis studies in the gas phase have been summarized in several review papers. In a comprehensive review by Sauer [4], a review presented by Firestone and Dorfman [5] in 1971 was referred to as the first review on gas-phase pulse radiolysis. Experimental techniques and results obtained were summarized by one of the present authors [6], with emphasis on an important contribution of pulse radiolysis to gas-phase reaction dynamics studies. Examples were chosen by Sauer [7] from the literature prior to 1981 to show the types of species that were investigated in the gas phase using pulse radiolysis technique. Armstrong [8] reviewed experimental data obtained from gas-phase pulse radiolysis together with those from ordinary steady-state radiolysis. Advances in gas-phase pulse radiolysis studies since 1981 were also briefly reviewed by Jonah et al. [9], with emphasis on an important contribution of this technique to free radical reaction studies. One of the present authors reviewed comprehensively the gas-phase collision dynamics studies of low-energy electrons, ions, excited atoms and molecules, and free radicals by means of pulse radiolysis method [1-3]. An important contribution of pulse radiolysis to electron attachment, recombination, and Penning collision studies was also reviewed in Refs. 10-15. 

In radiolysis a fraction of C H2 alkenes forms in bimolecular radical reactions. Source Refs. 18, 29, 108, 110, and 111. 

Holcman, J., E. Bjergbakke, and K. Sehested, The Importance of Radical-Radical Reactions in Pulse Radiolysis of Aqueous Car-bonate/Bicarbonate, Proc. 6th Tihany Symp. Radiat. Chem., 6, 149-153 (1987). 

Weinstein-Lloyd, J., and S. E. Schwartz, Low-Intensity Radiolysis Study of Free-Radical Reactions in Cloudwater H202 Production and Destruction, Environ. Sci. Techno ., 25, 791-800(1991). 

Radiation techniques are powerful tools1- for the study of free-radical reactions both in solution and in the solid state. In aqueous solution, the y-radiolysis of the solvent water gives rise to OH radicals, sol-... 

Elimination and rearrangement reactions of the primary radicals (see Sect. 11,1) that are slower than 2 x 10s s-1 are, therefore, suppressed at ordinary concentrations of oxygen (air-saturated [02] 2 x 10-4 M). Similarly, radical-radical reactions (see Sect. 11,2) cannot compete effectively with reaction 36, even at the high dose-rates of pulse radiolysis. Because the hydroxyalkyl radicals are nearly planar, two different peroxyl radicals are generated at optically active centers. 

Despite the present poor understanding of the primary processes, the radiolysis of carbohydrates is a unique way to generate carbohydrate radicals within the carbohydrate matrix. It has enabled some interesting chain reactions to be detected (see Sect. IV,1). Many radical reactions observed in aqueous solution are also observed in the solid state. In addition, there are reactions that are more pronounced in the solid state, and their products can be studied more readily than in the liquid state. 

The rate constants for 8 and 9 were determined by pulse radiolysis by adding known amounts of excess acid or H20-2 and measuring the pseudo-first order decay of hydrated electron absorption (15, 25). The rate constant for recombination of OH radicals (Reactions 19) was deter-... 

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