Question

Why are Grignard reactions important?

Answer 1

Because (i) they are relatively easy to perform; and (ii), they are one of the few reactions to form `C-C` bonds.

Explanation:

A Grignard reagent may be made from a hydrocarbyl halide as shown:

`R-X + Mg rarr R-MgX`

A carboxylic acid may be formed by pouring the Grignard onto dry ice:

`R-MgX + CO_2 rarr R-C(=O)O^(-)""^+(MgX)`

A `2""^@` alcohol may be made from an aldehyde:

`R'-MgX + H(O=)CR rarr R'-C(O^(-)""^+MgX)R`

A `3""^@` alcohol may be made from an ketone:

`R'-MgX + R_1C(=O)R_2 rarr R'-C(O^(-)""^+MgX)R_1R_2`

And from ethylene oxide, a `1""^@` alcohol may be isolated (i.e., the carbon chain is extended by 2 carbons):

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

Grignard reagents are remarkably easy to make given dry solvents, and they are reactive beasts.