By reaction of organic halides with magnesium

The mechanism of the reaction between organic halides and magnesium, leading to organomagnesium compounds, has been the subject of much speculation and study, and no little controversy. For the chemist wishing to prepare and use the organomagnesium compounds, information on the mechanism is especially relevant to two matters the nature and amount of by-products, and the stereochemistry of the organomagnesium product. 

Following the prophetic speculations of Kharasch and Reinmuth [A] and the crucial CIDNP experiments of the Amsterdam group [22], the main features of the mechanism are now clear. Electron transfer from the magnesium surface to adsorbed organic halide gives rise to alkyl radicals and halide ions. Further recombination steps lead to the alkylmagnesium halide. Two matters especially remain controversial whether the electron transfer step involves a discrete radical anion intermediate, and to what extent radicals leave the metal surface to diffuse into the solution. Recent arguments have been summarized [23, 24], commented on [25], and pursued [26], The implications for practical work may be summarized briefly as follows  

81% (optical purity 27%) 89% (optical purity 26%) 70% (optical purity 19%) 79% (optical purity 11 %) 

The following selection of preparations is representative of the main types of procedure for preparing organomagnesium compounds by the reaction of magnesium with organic halides. Other well-described preparations are listed in Table 3.2. Yields are not listed in Table 3.2, since in many cases only the yields of subsequent reactions are recorded they are in general high unless otherwise stated. 

Preparation of Grignard reagents by the reaction of magnesium with organic 

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