The Grignard reaction is a reaction an organic chemistry that adds an organomagnesium halide compound to a ketone or an aldehyde. The reaction forms a tertiary alcohol from a ketone or a secondary alcohol from an aldehyde. If formaldehyde is the starting reactant, then a primary alcohol is formed.
Grignard reactions can occur through a nucleophilic-addition mechanism or through a single-electron-transfer mechanism. The mechanism depends on how sterically hindered the beginning reactant is. When sterically hindered reactants are used, the Grignard reaction proceeds through a single-electron transport. Both mechanisms produce a carbocation intermediate that can be attacked by an organomagnesium halide. The reaction is then hydrolyzed with water or excess protons to convert the product into an alcohol.