Kinetics and Mechanisms of Radical Reactions

The kinetics and mechanisms of radical reactions important in combustion chemistry are best studied under conditions in which single reactions can be isolated rather than in flames where there are multiple pathways for formation and disappearance of the radicals. Reactions of C2 are of particular importance since recent laser saturation measurements in our laboratory (1) have shown that C2 a3IIu is present in oxyacetylene flames at concentrations on the order of 1016 molecules/cm3 (approximately 0.1 torr). Although concentrations of ground state C2 in flames are unknown and cannot be measured by the same technique due to spectroscopic constraints, we expect that C2 X3 g populations are at least comparable. Because of these relatively large concentrations the reactions of both species are of considerable importance in combustion chemistry. However, until recently very little was known about these reactions due to the difficulty of producing a clean source of C2 radicals. 

Extensive studies of the macroradicals structure and their reaction pathways were performed. Most investigations are concerned with deciphering of EPR spectra and the determination of radical structure 5—18). The number of EPR studies bearing on kinetics and mechanism of radical reactions is limited. 

Cheves Walling, too, was in the forefront of the newly bom study of vinyl polymerization process. As Earl Huyser relates in his dedication, Cheves obtained a PhD under Morris Kharash in 1939—a most propitious moment for a young man to arrive on the scene with a special talent for unraveling the mysteries of the kinetics and mechanisms of radical reactions. In his early years at the U. S. Rubber Company Laboratories, Cheves Walling contributed to the newly appreciated understanding of... 

Atkinson R, Darnall KR, Lloyd AC, et al. 1979. Kinetics and mechanisms of the reactions of the hydroxyl radical with organic compounds in the gas phase. Advances in photochemistry 11 375-488. 

Electroanalytical chemists and others are concerned not only with the application of new and classical techniques to analytical problems, but also with the fundamental theoretical principles upon which these techniques are based. Electroanalytical techniques are proving useful in such diverse fields as electro-organic synthesis, fuel cell studies, and radical ion formation, as well as with such problems as the kinetics and mechanisms of electrode reactions, and the effects of electrode surface phenomena, adsorption, and the electrical double layer on electrode reactions. 

X. Park, J. Y., Heaven, M. C, and Gutman, D. (1984). Kinetics and mechanism of the reactions of vinyl radical with molecular oxygen. Chem. Phys. Lett. 104,469. 

Hydroxyl and Oxygen Atoms, Mechanisms and Rate Constants of Elemen tary Gas Phase Reactions Involving (Avramenko and Kolesnikova) Hydroxyl Radical with Organic Compounds in the Gas Phase, Kinetics and Mechanisms of the Reactions of (Atkinson, Damall, Winter,... 

Once a chemical submodel has been developed, it must be tested extensively prior to its application in comprehensive computer models of an air basin or region. This is done by testing the chemical submodel predictions against the results of environmental chamber experiments. While agreement with the chamber experiments is necessary to have some confidence in the model, such agreement is not sufficient to confirm that the chemistry is indeed correct and applicable to real-world air masses. Some of the uncertainties include those introduced by condensing the organic reactions, uncertainties in kinetics and mechanisms of key reactions (e.g., of aromatics), and how to take into account chamber-specific effects such as the unknown radical source. 

Hydroxyl Radical with Organic Compounds in the Gas Phase, Kinetics and Mechanisms of the Reactions of (Atkinson. Darnall. Winer. 

Thornalley PJ, Vasak M (1985) Possible role for metallothionein in protection against radiation-induced oxidative stress. Kinetics and mechanism of its reaction with superoxide and hydroxyl radicals. Biochim Biophys Acta 827 36-44... 

Hynes, A.J., and P.H. Wine. 1991. Kinetics and mechanism of the reaction of hydroxyl radicals with acetonitrile under atmospheric conditions. J. Phys. Chem. 95 1232-1240. 

Kinetics and mechanism of the reaction may be studied on the basis of well-developed, clearly formulated statements of fundamental investigations in the branch of radical-chain processes. 

Atkinson, R. Damall, K.R., Lloyd, A.C., Winer, A.M., Pitts Jr., J.N. (1979) Kinetics and mechanisms of the reaction of the hydroxyl radicals with organic compounds in the gas phase. In Advances in Photochemistry. Volume II, Pitts Jr., J.N., Hammond, G.S., Golnick, K., Editors, John Wiley Sons, New York. pp.375 188. 

The kinetics and mechanism of the reaction of 4 with halocarbons (dichloro-, trochloro- and tetrachloromethane, various benzyl halides) have been reported Earlier work on pyridinyl radicals has been reviewed as well as the organic chemistry of stable free radicals This chapter will concentrate on developments of the past decade, since new techniques, described specifically, have increa our understanding of pyridinyl radical behavior considerably. 

Electrochemical methods are widely used to gain information about the kinetics and mechanisms of chemical reactions associated with the electron transfer at an electrode. A unique feature of these methods is that the electrode serves both as the means of generating an intermediate, for instance a radical ion, and as the means to monitor its reactions to products. 

Some of the most successful applications of LSV and CV are concerned with the study of the kinetics and mechanisms of the reactions of electrode generated intermediates and a large share of the electrochemical literature deals with this aspect of voltammetry [8,9,13-38,72]. The majority of electrochemical reactions include radical ions as the primary intermediates, and the reaction schemes describing the conversion of a substrate A to products are typically composed of one or two one-electron transfers and one or two chemical steps. The examples include cathodic hydrogenations, (-l-2e , +2H ") (see Chapter 6) and hydrodimerizations (-l-e , -t-H ) (see Chapter 21), and anodic additions (—2e , - -2Nu ) (see Chapter 24), dehydrodimerizations (—e , —H ) (see Chapter 22), and substitutions (—2e , +Nu , —H ) (see Chapter 24), where Nu is nucleophile)... 

The kinetics and mechanism of the reaction of methanol with bromine is not well known. The overall rate constant was found to depend either on the chemical composition or the pressure of the system, which may be explained by a change in the nature of the termination reaction involving bromine atoms (hetero- and homogenous recombination with other radicals).77,78 Results of a... 

Because of the sensitivity and selectivity of the ESR approach, it is a powerful method for studying free radicals in low concentrations in complex systems. ESR can be helpful in two ways to characterize and structurally identify radical intermediates and to obtain information on the kinetics and mechanisms of their reactions. These reactions can be very fast one of the main differences between ESR of biological free radicals and ESR of spin labels and metal ions is that in the former case one generally is dealing with transient paramagnetic species. 

Barnes, L, V. Bastian and K.H. Becker Kinetics and mechanisms of the reaction of OH radicals with dimethyl... 

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