Question

What can Grignard react with?

Answer 1

Typically we react Grignard reagents with carbonyl species.

Explanation:

The best way to make a carboxylic acid is to pour the Grignard reagent onto dry ice:

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

Grignards will react with aldehydes and ketones to give secondary and tertiary alcohols:

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

Grignards will react with epoxides to extend the carbon by 2 carbons:

`R-MgX + C_2H_4O rarr R-CH_2CH_2O^(-)""^(+)MgX`

The reaction with alkyl halides is generally unsuccessful. But Grignards will also react with any protic reagent, i.e. alcohols or water:

`RCH_2-MgX + D_2O rarr RCH_2D + MgXOD` `(D=""^2H)`

The water sensitivity of Grignard reagents is the reason why we take considerable precaution to perform these reactions under anhydrous conditions.