ABSTRACT
This chapter considers organomagnesium, organolithium and organocopper compounds. Organometallic compounds are enormously versatile reagents. When carbon is bonded to an electropositive metal, the carbon is nucleophilic and susceptible to attack by electrophiles. Reactivity depends on the nature of the metal atom, there being a steady decrease in reactivity with decrease in the electropositive character of the metal: organomagnesium compounds are less reactive than organolithium compounds. The negatively polarized carbon is a powerful nucleophilic centre and reacts with most electrophilic centres. Since many organic molecules contain an electrophilic carbon atom, this provides a general method of forming new carbon–carbon bonds. The chosen electrophilic centre is the carbonyl carbon atom of an ester. In the first step of the reaction, the magnesium atom of the Grignard reagent coordinates to the carbonyl oxygen of the ester. Alkyl halides possess an electrophilic carbon atom and are susceptible to nucleophilic substitution.
