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# bonds.

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.