Organo Magnesium Reagents – Grignard Reagent (R-Mg-X).

Organo Magnesium Reagents (Grignard Reagent) [R-Mg-X]

• The Bond which is present between the carbon atom of an organic group and the metal Magnesium is called as organo magnesium bond and the compounds are called as organo magnesium compounds.

• In organo Magnesium compounds the electro negativity of the carbon atom of an organic group is 2.5, while the electro negativity of the metal Mg is 1.23.

• In organo Magnesium compounds, the electro negativity differences between the carbon atom of an organic group and the metal Mg is 2.5 – 1.23 = 1.27 is high, results 35% ionization.

• High electro negativity of carbon atom than Mg metal negatively polarizes organo Magnesium bond towards carbon atom of an organic group results in the formation of carbon anion which acts as nucleophile as well as base.

• Due to High ionization of organo Magnesium metallic bond, the carbon anion which comes is act as strong nucliophile as well as strong base.

• Organo Magnesium compounds are syntheticall precursors for organo metallic reagents. Since they are used in the preparation of various organo metallic reagents Ex: Gillmann’s reagents.

• Due to High ionization or High polarisability of organo magnesium metallic bond, organo magnesium compounds (RMgX) are more reactive than organo cupper compounds (R2 Cu Li).

• The reactivity order of organo magnesium compounds, organo lithium compounds and organo Cupper compounds is as follows R-Li > R-Mg-X > R2CuLi.

• Most of the organo ‘Mg’ reagent reactions are similar to the reaction of organo lithium reagent. But differs in some reactions.