Q.A Grignard reagent is prepared by whose reaction on magnesium in presence of dry ether-

A Grignard reagent is made by leaving a solution of an alkyl (or aryl) halide in dry ether standing over pieces of magnesium metal: the metal gradually dissolves as it inserts into the C-X bond, giving the alkyl magnesium halide, R-MgX (iodomethane + Mg/dry ether gives methyl magnesium iodide, CH3MgI). Every reagent and every piece of glassware used must be scrupulously pure and dry. The reagent's C-Mg bond is covalent but strongly polarised, since carbon is more electronegative than magnesium: carbon carries a partial negative charge and magnesium a partial positive charge, written R(delta-)-Mg(delta+)-X. That polarisation is exactly why the alkyl group behaves as a nucleophile/carbanion-equivalent in every synthetic use of the reagent, and exactly why the reagent is so aggre …