Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

21. Aldehydes and Ketones: Nucleophilic Addition

Nitrile to Ketone

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Nitrile to Ketone

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2:20 minutes

Problem 28c

Textbook Question

Show how you would add a Grignard reagent to an ester or a nitrile to synthesize
(c) pentan-2-one.

Verified step by step guidance

Identify the target molecule, pentan-2-one, which is a ketone. The goal is to synthesize this compound using a Grignard reagent and either an ester or a nitrile as the starting material.

Choose an appropriate Grignard reagent. To form pentan-2-one, the Grignard reagent should add a two-carbon chain to the starting material. Use ethylmagnesium bromide (CH₃CH₂MgBr) as the Grignard reagent.

If starting with an ester, select an ester that will yield the desired ketone after the Grignard reaction. For pentan-2-one, use methyl propanoate (CH₃CH₂COOCH₃) as the ester. The Grignard reagent will add to the carbonyl carbon of the ester.

If starting with a nitrile, select a nitrile that will yield the desired ketone after the Grignard reaction. For pentan-2-one, use propanenitrile (CH₃CH₂CN). The Grignard reagent will add to the carbon of the nitrile group, forming an imine intermediate, which is then hydrolyzed to the ketone.

Perform the reaction: (1) React the Grignard reagent with the ester or nitrile under anhydrous conditions to form the intermediate. (2) For the ester, the intermediate will collapse to form the ketone directly. For the nitrile, hydrolyze the imine intermediate with aqueous acid to yield the ketone, pentan-2-one.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Grignard Reagents

Grignard reagents are organomagnesium compounds represented as R-MgX, where R is an organic group and X is a halogen. They are highly reactive nucleophiles that can add to electrophilic carbonyl groups, such as esters and nitriles, facilitating the formation of new carbon-carbon bonds. Understanding their reactivity is crucial for synthesizing ketones and other carbonyl compounds.

Ester Reactivity

Esters are organic compounds characterized by the functional group RCOOR', where R and R' are hydrocarbon chains. They can undergo nucleophilic addition reactions with Grignard reagents, leading to the formation of tertiary alcohols after hydrolysis. Recognizing the mechanism of this reaction is essential for synthesizing ketones like pentan-2-one from esters.

Nitrile Reactivity

Nitriles are compounds containing the cyano group (-C≡N) and can also react with Grignard reagents. When a Grignard reagent adds to a nitrile, it forms an intermediate imine, which can be hydrolyzed to yield a ketone. This pathway is significant for synthesizing ketones, providing an alternative route to the desired product.

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Related Practice

Textbook Question

Show how each transformation may be accomplished by using a nitrile as an intermediate. You may use any necessary reagents.

(b) cyclohexanecarboxamide → cyclohexyl ethyl ketone

Textbook Question

Show how each transformation may be accomplished by using a nitrile as an intermediate. You may use any necessary reagents.

Textbook Question

Show how you would synthesize octan-2-one from each compound. You may use any necessary reagents.

(f) CH₃(CH₂)₅CN

Textbook Question

Show how the following transformations may be accomplished in good yield. You may use any additional reagents that are needed.

(a) bromobenzene → propiophenone

(b) CH₃CH₂CN → heptan-3-one

Textbook Question

A ketone can be prepared from the reaction of a nitrile with a Grignard reagent. Describe the intermediate formed in this reaction, and show how it can be converted to a ketone.

Textbook Question

Show how each transformation may be accomplished by using a nitrile as an intermediate. You may use any necessary reagents.

(b) cyclohexanecarboxamide → cyclohexyl ethyl ketone

Show more practices