Reaction of organic halides with magnesium

Reaction with deuterium oxide, O-deuterated alcohols or acids is commonly used to provide evidence for the formation of organomagnesium compounds (e.g. see Ref. [3]). Although the presence of water normally inhibits the reaction of organic halides with magnesium, it is noteworthy that under appropriate conditions a Barbier procedure was successful [4] ... 

Grignard s fundamental investigations,92 as well as subsequent very extensive studies, have shown that the solvent plays an important part in the reaction of organic halides with magnesium. Diethyl ether has proved the most serviceable solvent in the majority of cases, but dipropyl, dibutyl, and diisopentyl ether, as well as dioxan and tetrahydrofuran have been used in special cases formals, e.g., diisopropoxy- and diisobutoxy-methane, may also be invoked in the synthesis of organomagnesium compounds.93... 

During the early years of Grignard chemistry some of the research was geared towards the use of solvents and/or solvent mixtures, other than diethyl ether in reactions of organic halides with magnesium. 

For this purpose solvent-free organomagnesium compounds were prepared by the reaction of organic halides with magnesium in benzene in the presence of catalytic amounts of AT, AT-dimethylaminobenzene. These reagents were then placed in a calorimeter, small portions of ethereal solvents were added, and the evolution of heat by solvation determined. 

Reactions of Organic Halides with Magnesium Metal... 

Of further interest is a comparison [81b] of the structure-reactivity profile for several reaction types (Fig. 3), such as (1) the Grignard reagent of organic halides with magnesium,... 

In contrast, for reaction of organic halides with metallic magnesium, Whitesides ( 7) found a poor correlation with the rates of tri-n-butyltin hydride, and a reasonable correlation, especially with primary bromides, with reduction potentials, suggesting the formation of RXT. Sodium naphthalene reductions also correlate with reduction potentials for primary halides (4b). Moreover, reaction rates are faster in solvents favoring loose ion pairs over tight, further evidence for an early transition state involving election transfer and little bond dissociation. (4c)... 

The organometalhc precursors required for the introduction of COj are preparatively accessible through reaction of organic halides with metallic lithium or magnesium, metal-halogen exchange, ortho-lithiation, transmetallation or by deprotonation of CH-acidic sites, as described in the sections following. 

In 1966, a method for the synthesis of organotin compounds by electrolysis of alkyl halides using a tin anode and a magnesium cathode was developed.94,95 Such electrochemical reactions have been studied extensively by Tuck and coworkers.9 These studies have been reviewed and a general mechanism proposed for this class of electrochemical reactions.9 The reactions of organic halides with a metal anode resemble oxidative addition reactions, Eqs. 7.19 - 7.20 ... 

The reaction of the organic halide with magnesium is carried out in a non-protic polar solvent, usually diethyl ether or THF. Typical by-products are RR, RH and R(-H) (alkene), resulting from coupling and disproportionation reactions of the organic moiety. Also, by-products resulting from solvent attack are sometimes formed, but usually to a lesser extent. 

In 1901, Victor Grignard, prepared an organomagnesium halide by the reaction of an organic halide with magnesium metal in dry ether. 

Solid-fluid reactions like the reaction of organic halides in solvents with solid magnesium occur at dislocations in the solid reactant. In most cases, alloys with some percentage of other metals and stressed material, hke magnesium turnings,... 

The discovery by Grignard that organic halides react with metallic magnesium to give nucleophilic organomagnesium compounds was a landmark in organic synthesis. The reaction of a halide with metallic magnesium in diethyl ether remains the principal method of synthesis. The order of reactivity is RI > RBr > RCl. 

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