Radicals from reactions

Maximum and minimum values for chain scission and backbone radical formation can be estimated by assuming complete abstraction or combination of the radicals from Reactions 2 and 3. 

Note that the relative distribution of isomers (see Table VII) although different at the two temperatures, becomes about the same when a radical scavenger is added. This is expected from the above picture. At 20°C. a significant part of the dimer yield is due to the combination of isolated radicals from reaction 8, but in reaction 8 abstraction of a secondary over a primary hydrogen is favored by 2.3 kcal.61 The data of Table VII are consistent with this and show that at 20 °C., 5,6-Me2Cio, 4Et-5MeC9, and 4,5-Et2Cs, which are products of secondary radical... 

Similar to the chain systems discussed above, formation of radicals from reactions of the stable reactants is required to initiate chemical reaction. In the H2-O2 system the initiation occurs mainly by the reaction... 

Electron paramagnetic resonance (EPR) has been used in kinetics to detect various states of atoms and radicals, which may be reactants, products or transient intermediates [17]. EPR has been used to detect vibrationally excited OH radicals from reactions such as... 

NO2 in the troposphere reacts with hydroxyl radicals (from reaction 8.10, via reactions 8.2, 8.6, and 8.10) to form nitric acid ... 

Further reaction with the HO2 radical (reactions 5.55 and 5.56) gave a hydro-tetraoxide that decomposed to dialdehydes and/or to dicarboxylic acids. In aliphatic hydrocarbons, the OH radical first abstracts a hydrogen atom from the chain. Subsequent addition of O2 and further reaction with the hydroperoxy radical from reaction 5.52 led to formation of ketones and aldehydes (reactions 5.55 and 5.56 Heller, 1995). 

Radicals such as 27 add to alkenes and abstract halogen from bromotrichloro-methane selectively [27], In each case, selectivities in excess of 10 1 are obtained and the observed product is as predicted based upon the proposed structure of the radical. The proximal methyl of the dimethylpyrrolidine protects one face of the radical from reaction. 

Let us compute the rate of formation of OH radicals from reactions 1-4. 0(1D) is sufficiently reactive that the pseudo-steady-state approximation can be invoked for its concentration. Thus... 

Based on thermochemical data tabulated elsewhere (45), the minimum threshold energy requirements for Reactions 50 and 51 are estimated as approximately 1.7 and 3.1 eV. Stabilized CHF26h F radicals from Reaction 47 would be scavenged by H2S. The species CHF2CH2 F is... 

Recent interest in this aspect of the subject commenced with the appearance in 1974 of a paper by Gilbert and Napper, in which solutions were reported for a special case of the Smith-Ewart differential difference equations, namely, the case where the loss of radicals from reaction loci occurs exclusively by processes which are kinetically of first order in radical concentration within the loci. Loss through bimolecular mutual termination of radicals is assumed either not to occur at all or, at most, to account for the loss of a negligible proportion of the propagating radicals. Radical loss is assumed to occur almost exclusively by processes such as diffusion from the reaction loci back into the external... 

When the solution contains propanol-2 in addition to N2O, nitrogen still is formed, but the silver particles do not dissolve. Under these conditions, the OH radicals from reaction 12 react with the alcohol, forming reducing radicals, see reaction 1, which in turn reduce the Agn intermediate. The net result is a silver catalyzed photoreaction between nitrous oxide and propanol-2 ... 

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