Grignard Reagent

What is the Grignard Reagent?

Few alkyl halides react with metal to produce compounds having carbon-metal bonds. The new compounds formed having carbon-metal bond are known as organo-metallic compounds. One of the most notable organo-metallic compounds is Alkyl magnesium halide, denoted by RMgX. It is also commonly known as Grignard reagent named after the scientist who discovered it, Victor Grignard. This discovery holds a vital importance in chemistry and it made the scientist, a noble prize winner.

This reagent is obtained by the reaction of an alkyl halide with Magnesium in presence of dry ether as shown below:

Grignard Reagent

Grignard Reagent

C2H5Br + Mg \(\rightarrow\) C2HMgBr (Grignard reagent)

In Grignard reagent, the bond between the carbon and magnesium pulls the shared pair of electrons from positively charged magnesium and thus makes the bond highly polar and reactive. The bond between Mg and halogen is ionic in nature. Grignard reagents are highly reactive and react with any source of a proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons. It is, therefore, necessary to avoid even traces of moisture from a Grignard reagent. However, this is also considered as a method to produce hydrocarbon from the Grignard reagent.

Grignard Reaction

The reaction between the Grignard reagent and an organic compound to produce organo-metallic compound is known as the Grignard reaction. The Grignard reagent functions as a nucleophile and attacks positively charged or an electrophilic carbon atom. Grignard reactions often start slowly as is common for reactions involving solids and solutions. The initiation follows an induction period during which reactive magnesium gets exposed to the organic reagents. After this induction period, the reactions can be highly exothermic. Mostly these reactions take place in an ethereal solvent.

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Practise This Question

Allyl halides react with metallic sodium in dry ether producing