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

13. Alcohols and Carbonyl Compounds

Grignard Reaction

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Grignard Reaction

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4:38 minutes

Problem 15d

Textbook Question

Show how you would synthesize following tertiary alcohol by adding an appropriate Grignard reagent to a ketone.
d. 2-cyclopentylpentan-2-ol

Verified step by step guidance

Identify the target molecule: The target molecule is 2-cyclopentylpentan-2-ol, which is a tertiary alcohol. Tertiary alcohols can be synthesized by reacting a ketone with a Grignard reagent.

Determine the structure of the ketone: To form the tertiary alcohol, the ketone must have the same carbon skeleton as the target molecule, minus the group added by the Grignard reagent. In this case, the ketone would be cyclopentyl methyl ketone (2-cyclopentylpropan-2-one).

Determine the Grignard reagent: The Grignard reagent must add the appropriate alkyl group to the ketone to form the tertiary alcohol. In this case, the Grignard reagent would be ethylmagnesium bromide (CH₃CH₂MgBr).

Write the reaction mechanism: The Grignard reagent (ethylmagnesium bromide) will attack the carbonyl carbon of the ketone (cyclopentyl methyl ketone), forming a tetrahedral alkoxide intermediate. This intermediate will then be protonated during the acidic workup to yield the tertiary alcohol.

Summarize the synthesis: Combine cyclopentyl methyl ketone with ethylmagnesium bromide in an anhydrous ether solvent, followed by an acidic workup (e.g., H₃O⁺), to synthesize 2-cyclopentylpentan-2-ol.

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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 that are highly reactive and used in organic synthesis to form carbon-carbon bonds. They are created by reacting an alkyl or aryl halide with magnesium metal in anhydrous ether. When added to carbonyl compounds like ketones, they can facilitate the formation of alcohols through nucleophilic addition.

Nucleophilic Addition to Ketones

Nucleophilic addition is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom in a carbonyl group. In the case of ketones, the carbonyl carbon is susceptible to attack by nucleophiles such as Grignard reagents, leading to the formation of an alkoxide intermediate. This intermediate can then be protonated to yield the corresponding alcohol.

Synthesis of Tertiary Alcohols

Tertiary alcohols are synthesized from ketones by adding two alkyl groups to the carbon atom of the carbonyl. When a Grignard reagent reacts with a ketone, it adds to the carbonyl carbon, resulting in a tertiary alcohol after protonation. The specific structure of the Grignard reagent determines the final structure of the tertiary alcohol produced.

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Related Practice

Textbook Question

Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.

(c)

Textbook Question

Show how you would use Grignard syntheses to prepare the following alcohol from the indicated starting material and any other necessary reagents.

(d) 2-cyclohexylethanol from bromocyclohexane

Textbook Question

Show how this 1° alcohol can be made from the following:

(e) an alkene

(f) ethylene oxide

Textbook Question

Show how you would synthesize the following primary alcohol by adding an appropriate Grignard reagent to formaldehyde.

(b)

Textbook Question

Point out the flaws in the following incorrect Grignard syntheses.

(c)

(d)

Textbook Question

A variety of organometallics, which as strong nucleophiles can react with epoxides, are introduced in Chapter 16. Predict the product of these reactions. [Hint: Assume the carbon–metal bond in each is ionic, with the carbon possessing the negative charge.]

(b)

Textbook Question

Predict the product of the following epoxide addition reactions.

(b)

Textbook Question

Addition to an epoxide occurs via an S_N2 reaction, but the stereochemistry of the epoxide is retained in the following reaction. Why?

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