Grignard reagents: Alkyl magnesium halides (RMgX) are called Grignard reagents.
Preparation of Grignard reagents: When a solution of alkyl halide (R—X) in ether is allowed to stand over magnesium turning for some time then metal gradually dissolves. In this reaction alkyl magnesium halide is formed. This compound is called Grignard reagent.