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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Problem 42

Textbook Question

Which of the following solvents are reasonable choices for a Grignard reaction? Justify your choices. [Hint: Carbonyls are good electrophiles.]

Verified step by step guidance

Grignard reagents are highly reactive organomagnesium compounds that are sensitive to moisture and protic solvents. Therefore, the choice of solvent is crucial for the success of a Grignard reaction.

The first structure is tetrahydrofuran (THF), a cyclic ether. Ethers are generally good solvents for Grignard reactions because they can stabilize the Grignard reagent through coordination with the oxygen atom, and they do not contain acidic protons that would react with the Grignard reagent.

The second structure is ethyl acetate, an ester. Esters are not suitable solvents for Grignard reactions because they contain a carbonyl group, which is a good electrophile and would react with the Grignard reagent, leading to unwanted side reactions.

The third structure is ethanol, an alcohol. Alcohols are protic solvents and contain acidic protons that would react with the Grignard reagent, destroying it. Therefore, ethanol is not a suitable solvent for Grignard reactions.

The fourth structure is diethyl ether, a common solvent for Grignard reactions. Like THF, diethyl ether is an aprotic solvent that can stabilize the Grignard reagent without reacting with it. It is often used in Grignard reactions due to its ability to dissolve both the Grignard reagent and the organic substrate.

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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 serve as nucleophiles in organic synthesis. They are formed by reacting alkyl or aryl halides with magnesium metal in anhydrous ether. Their reactivity allows them to attack electrophiles, such as carbonyl compounds, making them essential in forming new carbon-carbon bonds.

Solvent Properties

The choice of solvent in a Grignard reaction is critical because Grignard reagents are sensitive to moisture and can react with protic solvents, leading to their decomposition. Suitable solvents are typically non-polar and aprotic, such as diethyl ether or tetrahydrofuran (THF), which can stabilize the Grignard reagent without participating in the reaction.

Electrophilicity of Carbonyls

Carbonyl compounds, such as aldehydes and ketones, are good electrophiles due to the polarized carbon-oxygen double bond, where the carbon atom carries a partial positive charge. This makes them susceptible to nucleophilic attack by Grignard reagents, facilitating the formation of alcohols after subsequent hydrolysis. Understanding this reactivity is crucial for predicting the outcomes of Grignard reactions.

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Textbook Question

Predict the products of the following reactions.

(d) product of (c) + cyclopentylmagnesium bromide, then acidic hydrolysis

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Predict the product of the following reactions.

(a)

Textbook Question

You might expect that aldehydes and ketones could undergo the addition/elimination mechanism. With strong nucleophiles, however, nucleophilic addition is the only outcome. Why?

Textbook Question

Beginning with an amide, two different pathways produce the same compound. Predict the product of these two pathways.

Textbook Question

A student, when solving the following 'predict-the-product' question, made a common mistake by writing the answer shown here. Explain why this reaction would not work as written.

Textbook Question

Dimerization is a side reaction that occurs during the preparation of a Grignard reagent. Propose a mechanism that accounts for the formation of the dimer.

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?

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