Electron Transfer from a Cyclic Diaryliodine Species to Arenediazonium Salts. Evidence for the Intermediacy of 9−I−2 Structures in Iodine Atom Transfer Reactions<sup>1</sup>

Geahigan, K. B.; Taintor, Richard J.; George, B. M.; Meagher, Denise A.; Nalli, Thomas W.

doi:10.1021/jo980113p

Cited by 10 publications

(9 citation statements)

References 26 publications

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“…This trend is compellingly illustrated by the reaction of NaNO 2 with 1, 9 2, 31 3 14 and 4 9 in aqueous DMSO under similar conditions (eqn. (10)).…”

Section: Reactions With Nucleophilesmentioning

confidence: 99%

Cyclic diaryliodonium ions: old mysteries solved and new applications envisaged

Grushin

2000

Chem. Soc. Rev.

224

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“…This trend is compellingly illustrated by the reaction of NaNO 2 with 1, 9 2, 31 3 14 and 4 9 in aqueous DMSO under similar conditions (eqn. (10)).…”

Section: Reactions With Nucleophilesmentioning

confidence: 99%

Cyclic diaryliodonium ions: old mysteries solved and new applications envisaged

Grushin

2000

Chem. Soc. Rev.

224

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“…For instance, in the Sandmeyer reaction, the arenediazonium salt is converted to the corresponding aryl halide in a homolytic pathway, promoted by the presence of catalytic amounts of cuprous halide acting as an efficient reductant. In the most recent studies, the focus has been on the mechanistic aspects of heterolytic processes, − whereas less attention has been paid to the homolytic counterparts. − …”

Section: Introductionmentioning

confidence: 99%

“…In the most recent studies, the focus has been on the mechanistic aspects of heterolytic processes, [5][6][7][8][9][10] whereas less attention has been paid to the homolytic counterparts. [11][12][13][14] The present work is devoted to the study of the fundamental aspects of the homolytic dediazoniation pathway depicted in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Substituted Benzenediazonium Salts by Solvated Electrons in Aqueous Neutral Solution Studied by Pulse Radiolysis

Daasbjerg

Sehested

2002

J. Phys. Chem. A

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A pulse radiolysis study of six parasubstituted benzenediazonium salts, X−C6H4N2 + [X = COOC2H5, F, H, CH3, OCH3, and N(CH3)2], has been carried out in neutral aqueous solutions, where the principal reductant is the solvated electron. In the first step, the solvated electron reduces the diazonium salts to the corresponding diazenyl radicals, X−C6H4N2 • , in a diffusion-controlled process. On a short time scale, X−C6H4N2 • is either involved in an equilibrium reaction with the parent diazonium salt (K > 100 M-1) in which a (X−C6H4)2N4 • + adduct is formed or decays to the aryl radical, X−C6H4 • , through the expulsion of dinitrogen. Simulation of this kinetic scheme allows us to make a rough determination of the rate constants involved. The rate constants for the formation of the adducts are in the range (0.7−1.9) × 107 M-1 s-1, whereas the fragmentation rate constants are in the range (0.4−4.0) × 105 s-1. The aryl radicals subsequently attack the diazonium salts mainly at the terminal nitrogen atom with rate constants of (0.13−5.9) × 107 M-1 s-1, thereby forming the radical cations of the corresponding azobenzenes, (X−C6H4)2N2 • +, or eventually the corresponding OH adducts, (X−C6H4)2N2OH • , upon further reaction with water. These intermediates were identified in pulse radiolysis by generating the very same species through an alternative pathway involving oxidation of the parent azobenzenes. The reaction between the aryl radical and the salt exhibits a clear substituent effect in the sense that the reactivity increases as the electron-donating power of the substituent is enhanced. This is attributed to the stabilizing effect exerted by electron-donating groups on radical cations. Thus, the radical cations can be detected only for the methoxy and dimethylamino groups, whereas for the other substituents the transformation of (X−C6H4)2N2 • + to (X−C6H4)2N2OH • takes place instantaneously.

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“…In the most recent mechanistic studies, the focus has mainly been on the heterolytic processes, − whereas less attention has been paid to the homolytic counterparts − despite their great importance. One of the major difficulties associated with the investigation of homolytic processes is the extremely high reactivity of the diazenyl and aryl radicals produced as intermediates.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Substituted Benzenediazonium Salts by Hydrogen Atoms in Aqueous Acidic Solution Studied by Pulse Radiolysis

Daasbjerg

Sehested

2003

J. Phys. Chem. A

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A pulse radiolysis study of six parasubstituted benzenediazonium salts, X−C6H4N2 + [X = COOC2H5, F, H, CH3, OCH3, and N(CH3)2], has been carried out in strongly acidic aqueous solution (1 M HClO4), where the principal reductant is the hydrogen atom. Initially, H adducts of the diazonium salts are formed with rate constants of (2.3−9.0) × 108 M-1 s-1, followed by their decay to protonated aryl radicals without the intermediacy of the diazenyl radicals that are observed when the reductant is the solvated electron. After a deprotonation reaction, the thus formed aryl radicals attack the diazonium salt mainly at the terminal nitrogen atom to afford the radical cations of the corresponding azobenzenes, (X−C6H4)2N2 • +, or eventually the corresponding OH adducts, (X−C6H4)2N2OH • , upon further reaction with water. For the dimethylamino substituent, the basicity is so high that the protonated radical cation of 4,4‘-bis(dimethylamino)azobenzene is formed. Studies carried out at different pH values for this system lead to a determination of its pK a = 2.0. For X = COOC2H5, F, H, and N(CH3)2, the rate-controlling step is the deprotonation reaction to afford the aryl radicals, whereas for X = CH3 and OCH3, it is the fragmentation of the H adduct to afford the protonated aryl radical. The characteristics of the corresponding OH adducts of the diazonium salts are also described briefly.

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Electron Transfer from a Cyclic Diaryliodine Species to Arenediazonium Salts. Evidence for the Intermediacy of 9−I−2 Structures in Iodine Atom Transfer Reactions¹

Cited by 10 publications

References 26 publications

Cyclic diaryliodonium ions: old mysteries solved and new applications envisaged

Cyclic diaryliodonium ions: old mysteries solved and new applications envisaged

Reduction of Substituted Benzenediazonium Salts by Solvated Electrons in Aqueous Neutral Solution Studied by Pulse Radiolysis

Reduction of Substituted Benzenediazonium Salts by Hydrogen Atoms in Aqueous Acidic Solution Studied by Pulse Radiolysis

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Electron Transfer from a Cyclic Diaryliodine Species to Arenediazonium Salts. Evidence for the Intermediacy of 9−I−2 Structures in Iodine Atom Transfer Reactions1

Cited by 10 publications

References 26 publications

Cyclic diaryliodonium ions: old mysteries solved and new applications envisaged

Cyclic diaryliodonium ions: old mysteries solved and new applications envisaged

Reduction of Substituted Benzenediazonium Salts by Solvated Electrons in Aqueous Neutral Solution Studied by Pulse Radiolysis

Reduction of Substituted Benzenediazonium Salts by Hydrogen Atoms in Aqueous Acidic Solution Studied by Pulse Radiolysis

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Electron Transfer from a Cyclic Diaryliodine Species to Arenediazonium Salts. Evidence for the Intermediacy of 9−I−2 Structures in Iodine Atom Transfer Reactions¹