Advanced Topic 807 of 1102 Organic Chemistry
Grignard Reagents
Organomagnesium compounds that add to carbonyls to form new carbon-carbon bonds.
In-depth explanation of Grignard Reagents
Grignard reagents have the general formula RMgX, made by reacting an alkyl or aryl halide with magnesium metal in dry diethyl ether. The carbon bonded to magnesium is strongly nucleophilic and strongly basic because the C-Mg bond is highly polar. They add to carbonyl compounds to form new carbon-carbon bonds, giving secondary alcohols from aldehydes, tertiary alcohols from ketones, and carboxylic acids from carbon dioxide. Because they react with water and other protic compounds, the reaction must be carried out under strictly anhydrous conditions.
Going deeper: Grignard Reagents
Key ideas: RMgX forms from RX and magnesium turnings in dry ether; the C-Mg bond is highly polar, so carbon acts as a carbanion. Products: formaldehyde gives a primary alcohol, other aldehydes give secondary, ketones and esters give tertiary alcohols (ester adds twice), CO2 gives a carboxylic acid after acid workup, epoxides add two carbons. Water destroys it, giving the alkane.
Common mistakes and connections: Students use protic solvents or wet glassware, killing the reagent. Another common error is forgetting that the acidic proton of any OH, NH, COOH or terminal alkyne in the substrate quenches the reagent, so protection is needed. Links to carbanion chemistry, retrosynthesis and carbon chain extension.
Visualization of Grignard Reagents
The carbon nucleophile of RMgX attacks a carbonyl carbon forming a new C-C bond; acid workup gives an alcohol. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Methylmagnesium bromide adds to ethanal to give propan-2-ol after acidic workup.
Frequently asked questions about Grignard Reagents
What is Grignard Reagents?
Organomagnesium compounds that add to carbonyls to form new carbon-carbon bonds.
Is Grignard Reagents a beginner, intermediate or advanced topic?
Grignard Reagents is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Grignard Reagents?
Study these earlier topics in Organic Chemistry first: Cannizzaro Reaction, Tollens' Test, Fehling's Test.
What comes after Grignard Reagents?
The next topics in Organic Chemistry are Carboxylic Acids and Esters.
Can I practise Grignard Reagents with quizzes?
Yes. The interactive lesson includes a self-check question on Grignard Reagents, and the Organic Chemistry quiz draws on every topic in this area.
Where Grignard Reagents fits in Organic Chemistry
Grignard Reagents is topic 79 of 148 in Organic Chemistry.