Grignard reagent - Definition and Overview

A Grignard Reagent is an alkyl- or aryl- magnesium halide. It is important in the synthesis of carbon-carbon bonds. Grignard reagents undergo reactions with compounds containing carbonyl groups. These reactions create alcohols.

Victor Grignard won the 1912 Nobel Prize in Chemistry for his discovery of Grignard reagents.

Grignard reagents are formed by reacting alkyl or aryl halides with magnesium metal. This most commonly uses bromides, as they work the fastest of the readily available halides. Fluoride give normaly no reaction. The Grignar reaction is exothermic and because of a oxide layer on the magnesium the start of the reaction is sometimes delayed.

In reactions involving Grignard reagents, it is important to ensure that no water is present. It causes the reagent to decompose. Thus, most Grignard reactions occur in solvents such as ether or tetrahydrofuran, because the oxygen of these solvents stabilizes the magnesium reagent. The reagent may also react with the air, inserting an oxygen atom between the carbon base and the magnesium halide group. Thus, many of these reactions are carried out in nitrogen or argon atmospheres.

Grignard reaction mechanism between acetone and Grignard reagent—a bromide in this case. Notice that water is required to form the alcohol.

See also

• Organolithium reagent