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

10. Addition Reactions

Epoxide Reactions

Organic Chemistry

10. Addition Reactions

Epoxide Reactions

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2:52 minutes

Problem 53

Textbook Question

Under the right conditions, the following acid-catalyzed double cyclization proceeds in remarkably good yields. Propose a mechanism. Does this reaction resemble a biological process you have seen?

Verified step by step guidance

Step 1: Protonation of the carbonyl group - The acid catalyst (H⁺) protonates the oxygen atom of the ketone group, increasing the electrophilicity of the carbonyl carbon. This makes the carbonyl carbon more susceptible to nucleophilic attack.

Step 2: Formation of the first ring - The double bond in the molecule acts as a nucleophile and attacks the protonated carbonyl carbon, leading to the formation of a new C-C bond and the first cyclization. This step generates a carbocation intermediate.

Step 3: Rearrangement and second cyclization - The carbocation formed in the previous step undergoes a rearrangement, and another double bond in the molecule acts as a nucleophile to attack the carbocation, forming the second ring. This results in a bicyclic intermediate.

Step 4: Deprotonation and stabilization - The intermediate formed undergoes deprotonation to stabilize the structure, leading to the formation of the final bicyclic compound with an alcohol group.

Step 5: Biological resemblance - This reaction resembles biological processes such as terpene biosynthesis, where carbocation intermediates and cyclizations are key steps in forming complex cyclic structures.

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Key Concepts

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

Acid-Catalyzed Reactions

Acid-catalyzed reactions involve the use of an acid to increase the rate of a chemical reaction. In these reactions, the acid donates a proton (H+) to a reactant, enhancing its electrophilicity and facilitating bond formation. This mechanism is crucial in organic chemistry, particularly in reactions like esterification and cyclization, where the formation of cyclic structures is promoted by protonation of functional groups.

Cyclization Mechanisms

Cyclization mechanisms refer to the processes by which linear or branched molecules form cyclic structures. This can occur through various pathways, including nucleophilic attack, electrophilic addition, or radical processes. Understanding the specific steps involved in cyclization, such as the formation of new bonds and the rearrangement of electrons, is essential for predicting the products and yields of these reactions.

Biological Analogies in Organic Reactions

Many organic reactions can be likened to biological processes, particularly those catalyzed by enzymes. Enzymes often facilitate cyclization and other transformations in a highly efficient and selective manner, mimicking acid-catalyzed reactions in the lab. Recognizing these parallels can provide insights into reaction mechanisms and help in understanding how nature achieves complex transformations under mild conditions.

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Related Practice

Textbook Question

a. Propose a mechanism for the conversion of cis-hex-3-ene to the epoxide (3,4-epoxyhexane) and the ring-opening reaction to give the glycol, hexane-3,4-diol. In your mechanism, pay particular attention to the stereochemistry of the intermediates and products.

b. Repeat part (a) for trans-hex-3-ene. Compare the products obtained from cis- and trans-hex-3-ene. Is this reaction sequence stereospecific?

Textbook Question

Predict the major product when each reagent reacts with ethylene oxide.

(d) PhNH₂ (aniline)

(e) KCN (potassium cyanide)

(f) NaN₃ (sodium azide)

Textbook Question

The following reaction resembles the acid-catalyzed cyclization of squalene oxide. Propose a mechanism for this reaction.

Textbook Question

Predict the major products of the following reactions, including stereochemistry where appropriate.

(d) (2S,3R)-2-ethyl-2,3-dimethyloxirane + H⁺ / CH₃OH

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (vii) 1. mCPBA 2. H₂SO₄, H₂O

(d)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (vii) 1. mCPBA 2. H₂SO₄, H₂O

(k)

Textbook Question

There are two mechanisms by which each of the two enantiomers can form in the reaction shown in Figure 9.37. Show them.

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Textbook Question

Show an arrow-pushing mechanism for reactions 1–4 in Figure 9.37.

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