Why are Grignard reactions important?

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Answer 1 · 2016-06-10T20:17:44

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

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

$R - X + M g \to R - M g X$ $R-X + Mg rarr R-MgX$

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

$R - M g X + C O_{2} \to R - C (= O) O^{-}^{+} (M g X)$ $R-MgX + CO_2 rarr R-C(=O)O^(-)""^+(MgX)$

A $2^{\circ}$ $2""^@$ 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.