The alkyl magnesium halides are known as Grignard reagent. In general we can represent it as RMgX. Here both the alkyl group and halide are mono negative ions and the magnesium is in +2 oxidation state. Grignard reagent is a best reagent for conducting nucleophilic addition and substitution reactions. With carbonyl compounds it increases the number of carbons in the compound and gives an alkyl substitution.