Studies on the Grignard Reaction‐VII (<sup>1</sup>) on the Mechanism of the Grignard Reagent Formation and the Wurtz Side Reaction in Ether

Anteunis, M.; Schoote, J. van

doi:10.1002/bscb.19630721114

Cited by 12 publications

(1 citation statement)

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“…Several authors have proposed chain mechanisms before but not in connection with the S RN 1 pathway. [88,89,[127][128][129] A thorough discussion of the chain versus non-chain dilemma is presented in Van Klink's Ph. D. thesis.…”

Section: Introductionmentioning

confidence: 99%

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

et al. 2010

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Both SRN1‐type reactions and Grignard reagent formation are inhibited by trace amounts (with respect to the halide) of p‐dinitrobenzene (DNB) and other oxidising agents such as CuCl2 or dioxygen. Both are believed to be triggered by an electron‐transfer step. In this report we examine the patterns of reactivity shared by these two types of reaction. Although the two reactions display an amazing number of similarities, the chain character of the Grignard reaction mechanism has been rejected by major contributors to this field. We have performed new experiments to explore the inhibiting effect associated with the addition of trace amounts of p‐dinitrobenzene during Grignard reagent formation. This inhibition involves very reactive nanoparticles of magnesium prepared by metal vapour synthesis. The magnesium slurries studied, in the absence of p‐dinitrobenzene, display no induction period at all. If the p‐dinitrobenzene is added to the solution containing magnesium slurries 25 min before adding the organic halide (here bromobenzene), the reaction is neatly inhibited but, if one waits long enough, the Grignard reagent is nevertheless formed. If, however, the same trace amounts of p‐dinitrobenzene are diluted in the organic halide and this mixture is added to the magnesium slurries, the inhibiting effect is far less pronounced. The addition of the nBu4NBr salt drastically diminishes the inhibiting power of DNB. These observations, in addition to the ESR study of radical anions formed in THF by the reaction of magnesium nanoparticles and DNB with various polyaromatics, suggest a mechanism for the observed inhibitions that involves a series of reversible adsorptions of the present species. This adsorption would depend on both thermodynamic and kinetic factors. Thermodynamics would favour the adsorption of DNB radical anions but C–X bond cleavage of the less strongly adsorbed aromatic radical anions would provide a kinetic driving force for displacing the equilibria in the direction of Grignard reagent formation. Salt effects could operate by displacing the equilibrium – adsorbed DNB radical anion or dianion versus solvated radical anion (with the counterion nBu4N+) – to the right, accelerating therefore the liberation of active sites on the magnesium surface. It appears that the inhibiting effect of the same compound finds its origin in two different molecular series of events in SRN1 and in Grignard reagent formation. The heterogeneous character of the Grignard reagent makes it possible to envision the possibility of active sites even on nanoparticles, whereas the inhibition of the SRN1 mechanism by DNB occurs in homogeneous solution.

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Section: Introductionmentioning

confidence: 99%

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

et al. 2010

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Grignard Reaction

2010

Comprehensive Organic Name Reactions and Reagents

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The Grignard reaction refers to the reaction of Grignard reagents with many kinds of electrophiles, including CO 2 to form carboxylic acid and nitriles or acyl halides to form ketones, carbonyl compounds to form alcohols. Because the Grignard reagent is equivalent to a carbanion, the preparation of Grignard reagent must be carried out in an anhydrous solvent that can dissolve but not react with the generated carbanion species. This reaction has wide application in organic synthesis and is one of the most popular reactions to form carbon‐carbon bonds.

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Electron transfer at the solid liquid interface; new insights on the mechanism of formation of the grignard reagent

Chanon

Négrel

Bodineau

et al. 1998

Macromolecular Symposia

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The strong inhibiting effect of trace quantities of selected compounds on the reaction between ultra fine particles of magnesium and alkyl halides in THF strongly suggests that the generally accepted linear mechanism should be replaced by a chain mechanism.The reactivity of batteries of free radical clocks centered on an aliphatic skeleton displays unexpected leaving group effects. Such effects could be rationalized according to a variety of mechanistic schemes.The main ones are: 1) coexistence of polar and electron transfer routes, 2) participation of solvated electrons in the mechanism, 3) gradient of reactivity starting from the magnesium surface to the bulk solution. A series of experiments aiming at a choice between these possibilities is described.

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Studies on the Grignard Reaction‐VII (¹) on the Mechanism of the Grignard Reagent Formation and the Wurtz Side Reaction in Ether

Cited by 12 publications

References 9 publications

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

Grignard Reaction

Electron transfer at the solid liquid interface; new insights on the mechanism of formation of the grignard reagent

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Studies on the Grignard Reaction‐VII (1) on the Mechanism of the Grignard Reagent Formation and the Wurtz Side Reaction in Ether

Cited by 12 publications

References 9 publications

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

Grignard Reaction

Electron transfer at the solid liquid interface; new insights on the mechanism of formation of the grignard reagent

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Studies on the Grignard Reaction‐VII (¹) on the Mechanism of the Grignard Reagent Formation and the Wurtz Side Reaction in Ether

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism