GRIGNARD REAGENT

any of numerous organic derivatives of magnesium (Mg) commonly represented by the general formula RMgX (in which R is a hydrocarbon radical: CH3, C2H5, C6H5, etc.; and X is a halogen atom, usually chlorine, bromine, or iodine). The chemical behaviour of these substanceswhich are named after their discoverer, the French chemist Victor Grignardresembles that of the carbanions; e.g., the Grignard reagent methylmagnesium iodide (CH3MgI) is a strong base and a strong nucleophile, as is the methide ion (CH-3), a typical carbanion. Grignard reagents commonly are prepared by reaction of an organic halide with magnesium in a nitrogen atmosphere because the reagent is very reactive toward oxygen and moisture. Organic halides vary greatly in their rates of reaction with magnesium. For example, alkyl iodides generally react very rapidly, whereas most aryl chlorides react very slowly, if at all. Synthetic applications of highly reactive organometallic reagents such as alkyllithium (LiR) and Except for hydrocarbons, ethers, and tertiary amines, almost all organic compounds react with Grignard reagents. Many of these reactions are used for synthetic purposes, notably those with carbonyl compoundse.g., aldehydes, ketones, and acid chloridesand those with halogen compounds of certain metals e.g., zinc, cadmium, lead, mercuryto form the alkyl derivatives of the metals.