Single Electron Transfer and Nucleophilic Substitution

Electron transfer, in thermal and photochemical activation of electron donor-acceptor complexes in organic and organometallic reactions, 29,185 Electron-transfer, single, and nucleophilic substitution, 26,1 Electron-transfer, spin trapping and, 31,91 Electron-transfer paradigm for organic reactivity, 35, 193... 

Electron transfer, single, and nucleophilic substitution, 26, 1 Electronically excited molecules, structure of, 1, 365... 

R. Bacaloglu, C. A. Bunton, and F. Ortega,/. Am. Chem. Soc., 110, 3512 (1988). Single-Electron Transfer in Aromatic Nucleophilic Substitution in Reaction of 1-Substituted 2,4-Dinitronaphtlanenes with Hydroxide Ion. 

Mayer, M.U. and Breslow, R., Antihydrophobic evidence for the single electron transfer mechanism of nucleophilic substitution, /. Am. Chem. Soc., 1998, 120, 9098-9099. 

Since the publication of the review on Single Electron Transfer and Nucleophilic Substitution in this same series,1 reviews or research accounts have appeared concerning several particular points among those addressed here, namely, dynamics of dissociative electron transfer,2-6 single electron transfer and Sn2 reactions,2,7 9 and SRN1 reactions.10,11... 

Saveant, J-M. Single Electron Transfer and Nucleophilic Substitution, in Advances in Physical Organic Chemistry, Bethel, D., Ed., Academic Press New York, 1990, Vol. 26, pp. 1-130. 

The weird EC, CE, ECE. .. jargon of molecular electrochemists, a community well exposed to single electron transfer, draws a sharp distinction between electron-transfer ( E ) and chemical reactions ( C ). Should they now totally abandon this dichotomy and see, together with all molecular chemists, single electron transfer in every chemical reaction, particularly in every nucleophilic substitution ... 

Single-electron transfer and nucleophilic substitution in the pyridine series 92NJC131. 

Basicity is not the only general property of radical anions, anions, and dianions. Each may act as a nucleophile, a single-electron transfer agent, and as a base—sometimes all three As with conventionally generated bases, in what Baizer has dubbed secular chemistry, sterically hindered EGBs are useful because proton abstraction becomes favored over nucleophilic substitutions and additions. 

We have noted that both 5 2 and SnAr reactions may occur through SET processes. There is good evidence that the SnAc reaction may involve such a pathway also. Figure 8.55 shows species identified by Bacaloglu and coworkers in a fast kinetic spectroscopy study of the reaction of hydroxide ion with l-chloro-2,4,6-trinitrobenzene (picryl chloride, 71). D ending on reaction conditions, these workers could see transients ascribed to the n complex (72), an intermediate produced by single electron transfer (73), and one or more cr complexes (74, 75). In addition, evidence was obtained for the reversible formation of a phenyl carbanion (76) and a dianion (77) that probably do not lead directly to the substitution product (78). Further support for the role of SET processes in SNAr reactions comes from the detection of radical intermediates by EPR spectrometry and by correlations of reactivity with the oxidation potentials of the nucleophiles in some studies. ... 

The reactivities of the substrate and the nucleophilic reagent change vyhen fluorine atoms are introduced into their structures This perturbation becomes more impor tant when the number of atoms of this element increases A striking example is the reactivity of alkyl halides S l and mechanisms operate when few fluorine atoms are incorporated in the aliphatic chain, but perfluoroalkyl halides are usually resistant to these classical processes However, formal substitution at carbon can arise from other mecharasms For example nucleophilic attack at chlorine, bromine, or iodine (halogenophilic reaction, occurring either by a direct electron-pair transfer or by two successive one-electron transfers) gives carbanions These intermediates can then decompose to carbenes or olefins, which react further (see equations 15 and 47) Single-electron transfer (SET) from the nucleophile to the halide can produce intermediate radicals that react by an SrnI process (see equation 57) When these chain mechanisms can occur, they allow reactions that were previously unknown Perfluoroalkylation, which used to be very rare, can now be accomplished by new methods (see for example equations 48-56, 65-70, 79, 107-108, 110, 113-135, 138-141, and 145-146)... 

C-Methylation products, o-nitrotoluene and p-nitrotoluene, were obtained when nitrobenzene was treated with dimethylsulfoxonium methylide (I)." The ratio for the ortho and para-methylation products was about 10-15 1 for the aromatic nucleophilic substitution reaction. The reaction appeared to proceed via the single-electron transfer (SET) mechanism according to ESR studies. 

It has been well known since the pioneering work of Bunnett59 that some nucleophilic aromatic substitutions can be catalyzed by single electron transfer. Electrochemistry was shown60,61 to be an efficient technique both for inducing reactions and for determining mechanisms and thermodynamic data concerning equilibria in the overall process. 

Nucleophilic substitution, in phosphate esters, mechanism and catalysis of, 25,99 Nucleophilic substitution, single electron transfer and, 26, 1 Nucleophilic vinylic substitution, 7,1... 

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