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

16. Conjugated Systems

Allylic Halogenation

Organic Chemistry

16. Conjugated Systems

Allylic Halogenation

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3:05 minutes

Problem 38a

Textbook Question

A student was studying terpene synthesis, and she wanted to make the compound shown here. First she converted 3-bromo-6-methylcyclohexene to alcohol A. She heated alcohol A with sulfuric acid and purified one of the components (compound B) from the resulting mixture. Compound B has the correct molecular formula for the desired product.
a. Suggest how 3-bromo-6-methylcyclohexene might be converted to alcohol A.

Verified step by step guidance

Step 1: Analyze the structure of 3-bromo-6-methylcyclohexene. The bromine atom is attached to the cyclohexene ring, and the methyl group is at position 6. To convert this compound to alcohol A, the bromine atom must be replaced with a hydroxyl group (-OH). This suggests a nucleophilic substitution reaction.

Step 2: Choose an appropriate reagent for nucleophilic substitution. A common method to replace a bromine atom with a hydroxyl group is to use aqueous sodium hydroxide (NaOH) or potassium hydroxide (KOH) under heating conditions. This reaction proceeds via an SN2 or SN1 mechanism depending on the reaction conditions and the structure of the substrate.

Step 3: Consider the reaction mechanism. In this case, the cyclohexene ring is allylic, which stabilizes a carbocation intermediate. Therefore, the reaction is likely to proceed via an SN1 mechanism. The bromine atom leaves, forming a carbocation intermediate, which is then attacked by the hydroxide ion to form alcohol A.

Step 4: Verify the structure of alcohol A. The product should have the hydroxyl group (-OH) attached to the same carbon where the bromine atom was originally located. The structure of alcohol A matches this description, with the hydroxyl group replacing the bromine atom.

Step 5: Ensure reaction conditions are suitable. The reaction should be carried out in a polar protic solvent (e.g., water or ethanol) to stabilize the carbocation intermediate and facilitate the nucleophilic attack by hydroxide ions.

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Key Concepts

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

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom, replacing a leaving group. In the case of converting 3-bromo-6-methylcyclohexene to alcohol A, a nucleophile, such as hydroxide ion (OH-), can displace the bromine atom, resulting in the formation of an alcohol. This reaction is crucial for understanding how to manipulate functional groups in organic synthesis.

Alcohol Formation

Alcohols are organic compounds characterized by the presence of one or more hydroxyl (-OH) groups. The conversion of alkenes or alkyl halides to alcohols is a common transformation in organic synthesis. In this scenario, the formation of alcohol A from 3-bromo-6-methylcyclohexene involves the addition of water or a hydroxide ion, which is essential for creating the desired functional group for further reactions.

Acid-Catalyzed Dehydration

Acid-catalyzed dehydration is a reaction where an alcohol is converted into an alkene through the removal of a water molecule, typically facilitated by an acid like sulfuric acid. In the context of the question, heating alcohol A with sulfuric acid leads to the formation of compound B, which is an important step in synthesizing the desired terpene. Understanding this mechanism is vital for predicting the products of reactions involving alcohols.

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Related Practice

Textbook Question

Predict the products of the following reactions.

(g) 1-(bromomethyl)-2-methylcyclopentene, heated in methanol

Textbook Question

Show how the reaction of an allylic halide with a Grignard reagent might be used to synthesize the following hydrocarbons.

a. 5-methylhex-1-ene

Textbook Question

Show how the reaction of an allylic halide with a Grignard reagent might be used to synthesize the following hydrocarbons.

b. 2,5,5-trimethylhept-2-ene

Textbook Question

When Br2 is added to buta-1,3-diene at –15 °C, the product mixture contains 60% of product A and 40% of product B. When the same reaction takes place at 60 °C, the product ratio is 10% A and 90% B.

a. Propose structures for products A and B. (Hint: In many cases, an allylic carbocation is more stable than a bromonium ion.)

b. Propose a mechanism to account for formation of both A and B.

c. Show why A predominates at –15 °C and B predominates at 60 °C.

Textbook Question

Show how you might synthesize the following compounds starting with bromobenzene, and alkyl or alkenyl halides of four carbon atoms or fewer.

c. dec-5-ene

Textbook Question

Predict the products of the following reactions.

(g) 1-(bromomethyl)-2-methylcyclopentene, heated in methanol

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