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Also known as: Grignard Reagent Addition
Discovered by Victor Grignard (1900)
The Grignard reagent (RMgBr) is a powerful organometallic nucleophile that adds to carbonyl compounds. Formaldehyde → 1° alcohol, aldehydes → 2° alcohol, ketones → 3° alcohol, esters → 3° alcohol (two equivalents add). Nobel Prize 1912.
Grignard reagent preparation: An alkyl halide reacts with Mg metal in anhydrous ether to form the organomagnesium halide (R-MgBr).
Must be completely anhydrous — water destroys Grignard
Nucleophilic addition: The carbanion equivalent (R⁻) from the Grignard attacks the electrophilic carbonyl carbon, forming an alkoxide.
C-C bond forming step
Acid workup (H₃O⁺): Protonation of the magnesium alkoxide to give the free alcohol.
Separate step — add acid after reaction complete
Benzaldehyde + CH₃MgBr
Et₂O, then H₃O⁺
1-Phenylethan-1-ol
Acetone + PhMgBr
THF, then H₃O⁺
2-Methyl-2-phenylpropan-2-ol
CO₂ + CH₃MgBr
Et₂O, then H₃O⁺
Acetic acid
One of the most important C-C bond-forming reactions in organic synthesis. Foundational tool for building carbon skeletons.