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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4:51 minutes

Problem 16

Textbook Question

Propose a mechanism for the reaction of acetyl chloride with phenylmagnesium bromide to give 1,1-diphenylethanol.

Verified step by step guidance

Step 1: Identify the reactants and the product. Acetyl chloride (CH₃COCl) reacts with phenylmagnesium bromide (C₆H₅MgBr) in an ether solvent, followed by hydrolysis with H₃O⁺, to form 1,1-diphenylethanol.

Step 2: Recognize the role of phenylmagnesium bromide as a Grignard reagent. Grignard reagents are nucleophiles that attack electrophilic carbon atoms, such as the carbonyl carbon in acetyl chloride.

Step 3: The first phenylmagnesium bromide molecule attacks the carbonyl carbon of acetyl chloride, breaking the π bond of the C=O group. This forms a tetrahedral intermediate with a negatively charged oxygen atom and a phenyl group attached to the carbon.

Step 4: The chloride ion (Cl⁻) leaves as a good leaving group, resulting in the formation of a ketone intermediate, acetophenone (C₆H₅COCH₃).

Step 5: The second phenylmagnesium bromide molecule attacks the carbonyl carbon of the ketone intermediate, forming another tetrahedral intermediate. Upon hydrolysis with H₃O⁺, the negatively charged oxygen is protonated, yielding the final product, 1,1-diphenylethanol.

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Key Concepts

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

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, leading to the formation of a new bond. In this case, phenylmagnesium bromide acts as a nucleophile, attacking the carbonyl carbon of acetyl chloride, which is an electrophile due to the polarization of the carbon-oxygen double bond.

Grignard Reagents

Grignard reagents, such as phenylmagnesium bromide, are organomagnesium compounds that are highly reactive and serve as strong nucleophiles. They can react with various electrophiles, including carbonyl compounds, to form alcohols. Understanding their reactivity is crucial for predicting the outcome of reactions involving these reagents.

Protonation of Alkoxide

After the nucleophilic addition of phenylmagnesium bromide to acetyl chloride, an alkoxide intermediate is formed. This intermediate is then protonated, typically by adding water or an acid, to yield the final alcohol product, 1,1-diphenylethanol. This step is essential for converting the alkoxide into a stable alcohol.

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Related Practice

Textbook Question

List three different sets of reagents (each set consisting of a carbonyl compound and a Grignard reagent) that could be used to prepare each of the following tertiary alcohols:

Textbook Question

A student added an equivalent of 3,4-epoxy-4-methylcyclohexanol to a solution of methylmagnesium bromide in diethyl ether, and then added dilute hydrochloric acid. He expected that the product would be 1,2-dimethyl-1,4-cyclohexanediol. He did not get any of the expected product. What product did he get?

Textbook Question

List three different sets of reagents (each set consisting of a carbonyl compound and a Grignard reagent) that could be used to prepare each of the following tertiary alcohols:

Textbook Question

Addition of 1-bromobut-2-ene to magnesium metal in dry ether results in formation of a Grignard reagent. Addition of water to this Grignard reagent gives a mixture of but-1-ene and but-2-ene (cis and trans). When the Grignard reagent is made using 3-bromobut-1-ene, addition of water produces exactly the same mixture of products in the same ratios. Explain this curious result

Textbook Question

Two of the methods for converting alkyl halides to carboxylic acids are covered in Sections 20-8B and 20-8C. One is formation of a Grignard reagent followed by addition of carbon dioxide and then dilute acid. The other is substitution by cyanide ion, followed by hydrolysis of the resulting nitrile. For each of the following conversions, decide whether either or both of these methods would work, and explain why. Show the reactions you would use.

(e)

(f)

Textbook Question

Grignard reagents react slowly with oxetane to produce primary alcohols. Propose a mechanism for this reaction, and suggest why oxetane reacts with Grignard reagents even though most ethers do not.

Textbook Question

Draw the organic products you would expect to isolate from the following reactions (after hydrolysis).

(f)

(g)

Textbook Question

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

(g) cyclopentylphenylmethanol from benzaldehyde (Ph–CHO)

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