Question

Why is grignard reagent used?

Answer 1

Why? Because it is one of the few ways to make a `C-C` bond.

Explanation:

A Grignard reagent may be used to to make a carboxylate salt, 1 carbon longer than the Grignard reagent, simply by pouring the reagent onto dry ice:

`R-MgX+ CO_2(s) rarr RCO_2^(-)(MgX)^+`

(I almost wrote `R-MgX(aq)` in that equation; why would that have been embarassing?)

Grignard reagents can also react with epoxides, cyclic ethers with a 3-membered ring, to give an alcohol with a carbon chain 2 carbons longer than the Grignard reagent.

`R-MgX + C_2H_4O rarr RCH_2CH_2O^(-)(MgX)^+`

Secondary and tertiary alcohols can be elaborated by the action of Grignards on ketones and aldehydes.

Grignard reagents are (usually) very easy to make from an organic halide given simple precautions and dry solvents, and they are very reactive and reliable beasts to make `C-C` junctions.