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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6:43 minutes

Problem 23b

Textbook Question

Point out the flaws in the following incorrect Grignard syntheses.
(b)

Verified step by step guidance

Step 1: Analyze the starting material. The compound contains a bromine atom attached to a cyclohexane ring with a ketone and an ester functional group. The bromine atom is intended to form a Grignard reagent when treated with magnesium in ether.

Step 2: Understand the reaction conditions. The first step involves the formation of the Grignard reagent (R-MgBr) by reacting the bromine-containing compound with magnesium in ether. The second step involves the reaction of the Grignard reagent with formaldehyde (H₂C=O), followed by acidic workup (H₃O⁺).

Step 3: Identify the flaw in the synthesis. The ketone and ester functional groups present in the starting material are reactive toward Grignard reagents. When the Grignard reagent is formed, it will likely react intramolecularly with the ketone or ester group, leading to side reactions or decomposition, rather than reacting with formaldehyde as intended.

Step 4: Explain why the desired product cannot be formed. The Grignard reagent is highly nucleophilic and will attack the electrophilic carbonyl groups (ketone and ester) within the same molecule, preventing the reaction with formaldehyde. This intramolecular reaction disrupts the intended synthesis pathway.

Step 5: Suggest a correction. To avoid this issue, the ketone and ester groups should be protected before forming the Grignard reagent, or a different synthetic route should be chosen that does not involve the formation of a Grignard reagent in the presence of reactive carbonyl groups.

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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 to form carbon-carbon bonds. They are created by reacting alkyl or aryl halides with magnesium in dry ether. Understanding their reactivity is crucial, as they can react with electrophiles, including carbonyl compounds, to form alcohols. In the given synthesis, the presence of a carbonyl group is essential for the reaction to proceed correctly.

Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile to form a new bond. In the context of Grignard reactions, the Grignard reagent acts as a nucleophile, attacking the electrophilic carbon of a carbonyl compound. The failure to recognize the correct electrophile or the presence of incompatible functional groups can lead to flawed syntheses, as seen in the provided example.

Functional Group Compatibility

Functional group compatibility refers to the ability of different functional groups to coexist and react without interfering with each other. In organic synthesis, certain groups can be sensitive to the conditions or reagents used, leading to undesired reactions or products. In the provided synthesis, the presence of multiple oxygen-containing functional groups may hinder the desired reaction pathway, resulting in an incorrect product.

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Related Practice

Textbook Question

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

(c)

(d)

Textbook Question

A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups.

(b) Show how you would use reactions of Grignard reagents with ethyl formate to synthesize the following secondary alcohols.

(i) pentan-3-ol

(ii) diphenylmethanol

(iii) trans,trans-nona-2,7-dien-5-ol

Textbook Question

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

(a) octan-3-ol from hexanal, CH₃(CH₂)₄CHO

Textbook Question

Often, compounds can be synthesized by more than one method. Show how this 3° alcohol can be made from the following:

(a) two different ketones

Textbook Question

A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups.

(a) Propose a mechanism to show how the reaction of ethyl formate with an excess of allylmagnesium bromide gives, after protonation, hepta-1,6-dien-4-ol.

Textbook Question

Show how to make these deuterium-labeled compounds, using CD₃MgBr and D₂O as your sources of deuterium, and any non-deuterated starting materials you wish.

d. Ph(CD₃)₂COD

Textbook Question

Show how to make these deuterium-labeled compounds, using CD₃MgBr and D₂O as your sources of deuterium, and any non-deuterated starting materials you wish.

b. CH₃C(OH)(CD₃)₂

Textbook Question

Show how to make these deuterium-labeled compounds, using CD₃MgBr and D₂O as your sources of deuterium, and any non-deuterated starting materials you wish.

a. CH₃CH(OD)CD₃

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Point out the flaws in the following incorrect Grignard syntheses. (b)

Key Concepts

Grignard Reagents

Electrophilic Addition

Functional Group Compatibility

Watch next

Point out the flaws in the following incorrect Grignard syntheses.
(b)