On the Determination and Use of Reduction Potentials of Short-Lived Radicals. A Review

2000 ◽  
Vol 65 (6) ◽  
pp. 829-843 ◽  
Author(s):  
Henning Lund ◽  
Karen Skov ◽  
Steen Uttrup Pedersen ◽  
Torben Lund ◽  
Kim Daasbjerg
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Reaction Mechanisms ◽  
Nucleophilic Attack ◽  
Grignard Reaction ◽  
Hydroxide Ion ◽  
Reduction Sequence ◽  
Reduction Potentials ◽  
Srn1 Reaction

A method, the "competition method", for the determination of reduction potentials and estimation of standard potentials for short-lived radicals is reviewed. Applications of the reduction potentials of radicals as arguments for reaction mechanisms are presented for the Grignard reaction, the photoreduction of ketones with alcohols, and the SRN1 reaction. Reductions induced by hydroxide ions are discussed in more detail, and the classic reaction between nitrosobenzene and hydroxide ion in aqueous solution is used as an example of such a reaction. A nucleophilic attack by hydroxide ion rather than an electron transfer initiates the reduction sequence. A review with 26 references.

Dissociative electron transfer in polychlorinated aromatics. Reduction potentials from convolution analysis and quantum chemical calculations

2016 ◽  
Vol 18 (32) ◽  
pp. 22573-22582 ◽  
Author(s):  
Piotr P. Romańczyk ◽  
Grzegorz Rotko ◽  
Stefan S. Kurek
Keyword(s):  
Electron Transfer ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Redox Potentials ◽  
Dissociative Electron Transfer ◽  
Reduction Potentials ◽  
Polychlorinated Benzenes

The combination of convolution analysis and quantum-chemical calculations at DFT and CCSD(T)-F12 levels allows the determination of standard redox potentials and the mechanism type of dissociative ET in environmentally relevant polychlorinated benzenes.

Substitution Reactions of Nitrothiophens. III. Radical and Ionic Reactions of 4- and 5-Nitro-2-thienyl-methyl and -ethyl Chlorides and Acetates

1979 ◽  
Vol 32 (12) ◽  
pp. 2647 ◽  
Author(s):  
PJ Newcombe ◽  
RK Norris
Keyword(s):  
Electron Transfer ◽  
Nucleophilic Attack ◽  
Coupling Reactions ◽  
Substitution Reactions ◽  
Radical Coupling ◽  
Ionic Substitution ◽  
Substitution Process ◽  
Nitro Derivatives ◽  
Srn1 Reaction ◽  
Coupling Processes

The reactions of 4-nitro-2-thienyl-methyl and -ethyl chlorides and acetates with lithium 2-nitropropan-2-ide (1) give excellent yields of the C-alkylates, 2-(2-methyl-2-nitropropyl)- and 2-(1,2-dimethyl-2-nitropropyl)-4-nitrothiophen. These reactions proceed by a novel ionic substitution process involving initial nucleophilic attack on the thiophen ring. The 5-nitro derivatives react to give complex mixtures of products, which arise from SRN1, SN2, elimination, electron transfer and radical coupling processes. For example, 2-(1-chloroethyl)-5-nitrothiophen (23) reacts with the salt (1) under nitrogen to give the C-alkylate, 2-(1,2-dimethyl-2-nitropropyl)-5-nitrothiophen (24), formedby an SRN1 reaction, the alkene, 2-(1,2-dimethylprop-1-enyl)-5-nitrothiopen (25), derived from (24) by elimination of nitrous acid, 1-(5-nitro-2-thienyl)ethanone (26) and 1-(5-nitro-2-thienyl)ethanol(27) produced by SN2 O-alkylation, and 2,2'-(1,2-dimethylethene-1,2-diyl)bis(5-nitrothiophen) (28) formed by electron transfer and radical coupling reactions.

Kinetics and mechanism of phenoxide anions addition to 4-nitrobenzofurazan in aqueous solution

2017 ◽  
Vol 95 (7) ◽  
pp. 723-728 ◽  
Author(s):  
S. Ben Salah ◽  
T. Boubaker ◽  
R. Goumont
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Rate Constants ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
Single Electron ◽  
Single Electron Transfer ◽  
Hydroxide Ion ◽  
Order Rate

Second-order rate constants (k1) for the σ-complexation of 4-nitrobenzofurazan 1 with four 4-X-substituted phenoxide anions 2a–2d (X = OCH3, CH3, H and Cl) were measured in aqueous solution at 20 °C. Using this series of phenoxide anions as a reference, the electrophilicity parameter (E) of this electrophile 1 has been evaluated according to Mayr’s approach. With the E value of –9.42, Mayr’s equation was found to correctly predict the rate constants for the reactions of 1 with hydroxide ion in H2O and a 1:1 ratio of H2O to CH3CN. However, the large βnuc value of 1.12 obtained in the present work is clearly consistent with a single electron transfer (SET) mechanism.

Article

1999 ◽  
Vol 77 (4) ◽  
pp. 459-462
Author(s):  
J Andraos ◽  
Y Chiang ◽  
S J Eustace ◽  
A J Kresge ◽  
S W Paine ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carbonyl Group ◽  
Flash Photolysis ◽  
Isotope Effects ◽  
Nucleophilic Attack ◽  
Hydroxide Ion ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

Five ketenes, phenyl(ethyl)ketene, phenyl(methylthio)ketene, diphenylketene, pentafluorophenylketene, and 1-naphthylketene, were generated flash photolytically and solvent isotope effects (H2O vs. D2O) on their hydroxide-ion-catalyzed hydration in aqueous solution were determined. The values obtained are all weakly inverse and closely similar (kHO/kDO = 0.76-0.97), as expected for these fast, hydroxide-ion-consuming reactions, known to proceed by nucleophilic attack of hydroxide on the ketene carbonyl group. The characteristic magnitude of these isotope effects should prove useful in identifying new examples of this reaction.Key words: ketenes, flash photolysis, photo-Wolff reaction, solvent isotope effects on hydroxide ion consumption.

Reduction potentials of pentaammine complexes of cobalt(III), rhodium(III) and iridium(III): physical correlations

1983 ◽  
Vol 36 (7) ◽  
pp. 1327 ◽  
Author(s):  
NJ Curtis ◽  
GA Lawrance ◽  
AM Sargeson
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Electron Transfer ◽  
Magnetic Resonance ◽  
Large Range ◽  
Outer Sphere ◽  
Base Hydrolysis ◽  
Reduction Potentials ◽  
Nuclear Magnetic Resonance Spectra ◽  
Physical Correlations

The reduction potentials of a large range of [M(NH3)5L]π+ complexes (M = CoIII, RhIII, IrIII) have been determined in aqueous solution (μ 0.1 M, NaClO4). Irreversible reductions span the range from + 0.22 to -0.47 V for cobalt(III) complexes and from -0.86 to -1.45 V for rhodium(III),and occur near -1.7 V for iridium(III), determined against the standard (KCl) calomel electrode. Despite several reports to the contrary in the literature, no correlations exist of E� with absorption spectra (Co and Rh), nuclear magnetic resonance spectra [δ(1HN), Co, Rh, Ir, and δ (59Co)], vibrational spectra [v(Co-N)], or rates of aquation and base hydrolysis (Co, Rh, Ir). Complexes which undergo outer-sphere [e.g., with Ru(NH3)62+] and predominantly inner-sphere (e.g., with VZ+aq) homogeneous electron transfer can be distinguished by the presence or absence of a correlation of In kex with E� respectively, consistent with the expectations of the Marcus-Hush theory of outer-sphere electron transfer.

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