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

Imine vs Enamine

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Imine vs Enamine

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2:56 minutes

Problem 41a

Textbook Question

Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the acetonides formed from these diols with acetone under acid catalysis.

Verified step by step guidance

Step 1: Recognize the functional groups in the diol provided in the image. The molecule contains two hydroxyl (-OH) groups on adjacent carbons, making it a 1,2-diol.

Step 2: Understand the reaction mechanism. Under acid catalysis, acetone reacts with the 1,2-diol to form an acetal (specifically an acetonide). The reaction involves the formation of a cyclic structure where the diol protects the carbonyl group of acetone.

Step 3: Protonation of acetone occurs first under acidic conditions, increasing the electrophilicity of the carbonyl carbon. This facilitates the nucleophilic attack by one of the hydroxyl groups of the diol.

Step 4: After the nucleophilic attack, a hemiacetal intermediate is formed. The second hydroxyl group of the diol then reacts with the hemiacetal, leading to the formation of a cyclic acetal (acetonide).

Step 5: The final acetonide structure will be a six-membered ring formed by the diol and acetone, with the oxygen atoms from the diol incorporated into the ring. This cyclic acetal serves as a protecting group for the diol.

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Key Concepts

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

Acetals and Their Formation

Acetals are organic compounds formed when an aldehyde or ketone reacts with an alcohol in the presence of an acid catalyst. This reaction involves the nucleophilic attack of the alcohol on the carbonyl carbon, leading to the formation of a hemiacetal, which can further react with another alcohol molecule to yield the acetal. Understanding this process is crucial for recognizing how acetals can protect functional groups in organic synthesis.

Protecting Groups in Organic Chemistry

Protecting groups are temporary modifications used to shield reactive functional groups during chemical reactions. In the case of 1,2-diols, acetals serve as protecting groups by preventing oxidation or other reactions that could alter the diol's structure. This strategy allows chemists to selectively carry out reactions on other parts of a molecule without interference from the protected functional group.

Acetonides

Acetonides are specific types of acetals formed when acetone reacts with 1,2-diols. The resulting acetonide structure is particularly stable and is commonly used in organic synthesis to protect diols from unwanted reactions. Recognizing the formation and properties of acetonides is essential for understanding their role in synthetic pathways and their utility in organic chemistry.

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Related Practice

Textbook Question

Show how each of the following compounds could be prepared from the given starting material. Each requires a protecting group.

Textbook Question

Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the acetonides formed from these diols with acetone under acid catalysis.

Textbook Question

As discussed in Section 17.9.1, alkenes can be hydrogenated selectively in the presence of ketones. Suppose that was not the case, and suggest how you might use a protecting group strategy to generate A from B.

Textbook Question

Show how you would synthesize the following derivatives from appropriate carbonyl compounds.

(d)

Textbook Question

What starting materials are required to synthesize the following compounds, using the Fischer indole synthesis?

Textbook Question

Show what amines and carbonyl compounds combine to give the following derivatives.

(d)

Textbook Question

Show what amines and carbonyl compounds combine to give the following derivatives.

(f)

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