And single electron transfer

B. Reductions by Hydrides, Metals and Single-Electron-Transfer (SET)... 

As for the salt formation and single-electron transfer, thermodynamics for simple redox processes may be applied to predict their selectivity. As a first approximation, a cation with red lower and higher than 0.2 V would give a salt and a radical pair, respectively, when combined with [2 ]. In practice, the cations which were found to give salts with [2 ] have red values more negative than —0.8 V. On the other hand, quantitative single-electron transfer has been observed from [2 ] to the heptaphenyltropylium ion which is relatively unstable p/fR+ —0.54 in methanol (Battiste and Barton, 1968) and E ed —0.30 V vs. Ag/Ag in acetonitrile (Kitagawa et al., 1992). 

There are several other active topics under examination in our laboratory, for example, surface modification of polymers under phase transfer catalyzed reactions and single electron transfer phase transfer catalyzed polymerizations. The limited space, however, precludes discussion here. 

The transformation of oxiranes into other oxygen-containing heterocyclic systems (e.g., cyclic ethers, dioxolanes, orthoesters, lactones, and cyclic carbonates), via a variety of heterolytic, homolytic, enzymatic, and single-electron transfer processes, has been reviewed <2004RJ01227>. 

They have compared the reaction energy profiles of five different reaction paths, including oxidative insertion, nucleophilic substitution, and single-electron transfer mechanisms involving radical species, both in the gas phase as well as using an electrostatic continuum model to include the effect of a solvent in an approximate fashion (Structures 3-5). 

Scheme 42 Synthesis of diiodo poly(vinyl chloride) (PVC) by combination of ITP and single electron transfer (SET) with iodoform in the presence of Na2S204...

In Chapter 24, Paradisi and Scorrano present their results on the effect of reaction conditions on the competition between nucleophilic substitution and single electron transfer for reaction of alkoxides with p-nitro-chlorobenzene. The substitution pathway is favored by excluding oxygen and by adding a crown ether. The authors suggest that the crown enhances reactivity of the alkoxide by removing ion association and giving a free... 

Relationship between Nucleophilic Reactions and Single-Electron Transfer Application to Reactions of Radical Cations... 

The polymerization of NVK and related monomers was examined using controlled radical polymerization methods, such as atom transfer radical polymerization, single electron transfer, and single electron transfer initiation followed by a RAFT chain transfer [16]. 

Atom Transfer Radical Polymerization (ATRP) and Single-Electron Transfer-Living Radical Polymerization (SET-LRP)... 

The direct trifluoromethylation of thiophene can be performed under electro-phihc and radical conditions. The electrophilic reaction proceeded in the gas phase using trifluoromethyl cations obtained from CF4 under radiolysis ( °Co y-rays) [44], The selectivity trend for thiophene in the gas phase follows the order C2>C3>S1. The major products of this transformation were found to be monosubstituted trifluo-romethylthiophenes 78 and 79 (<20 % yield) [45], It has been proposed that the trifluoromethylation proceeds through electrophilic substitution and single-electron transfer mechanisms. 

In the past two years a number of papers have appeared in which EPR was used to study redox processes involving transition metal oxides (used either as catalysts or as supports for other oxides and metal particles) and single electron-transfer steps. The paramagnetic species formed at the gas-solid or liquid-solid... 

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