Grignard Reagent

Preparing Grignard reagents

A halogenoalkane is dissolved in dry ether and reacted with magnesium to produce the reactive Grignard reagent

Preperation of Grignard reagent equation

CH₃CH₂I + Mg → CH₃CH₂MgI

Reactivity of Grignard compounds

Grignard reagents are highly reactive; the alkyl group (R group) can be considered to have a negative charge and behaves as a nucleophile.

Grignard reagent structure

R–[+MgI]

Grignard reaction with methanal

• Grignard reagents react with methanal to produce a primary alcohol.

• RMgI + HCHO →(H₂O)→ RCH₂OH + Mg(OH)I

Grignard reaction with long chain aldehydes

• Grignard reagents react with longer chain aldehydes to produce secondary alcohols.

• CH₃CH₂MgI + HCHO →(H₂O)→ CH₃CH₂CH₂OH + Mg(OH)I

Grignard reaction with ketones

• Grignard reagents react with ketones to produce tertiary alcohols.

• CH₃CH₂MgI + CH₃COCH₃ →(H₂O)→ CH₃CH₂C(CH₃)(OH)CH₃ + Mg(OH)I

Grignard reaction with carbon dioxide

• Grignard reagents react with carbon dioxide to produce carboxylic acids.

• CH₃CH₂MgI + CO₂ →(H₂O)→ CH₃CH₂COOH + Mg(OH)I