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

12. Alcohols, Ethers, Epoxides and Thiols

Ether Cleavage

Organic Chemistry

12. Alcohols, Ethers, Epoxides and Thiols

Ether Cleavage

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Problem 107

Textbook Question

Cleavage of the following ether produces the alcohol and haloalkane only, regardless of how much HBr is used. Thinking about the mechanism of the reaction, explain why bromobenzene is not also a product of this reaction.

Verified step by step guidance

Identify the structure of the ether involved in the reaction. Ethers are compounds with an oxygen atom connected to two alkyl or aryl groups. In this case, the ether likely has a phenyl group and another alkyl group.

Understand the mechanism of ether cleavage with HBr. The reaction typically involves protonation of the ether oxygen, making it a better leaving group, followed by nucleophilic attack by bromide ion.

Consider the stability of the carbocation formed during the reaction. When the ether is cleaved, a carbocation is formed. The stability of this carbocation is crucial in determining the products of the reaction.

Recognize that phenyl cations are highly unstable. If the ether cleavage were to produce a phenyl cation, it would be very unstable and unlikely to form. Instead, the reaction favors the formation of a more stable carbocation.

Conclude that the reaction does not produce bromobenzene because the phenyl group remains attached to the oxygen, preventing the formation of a phenyl cation. The reaction instead produces an alcohol and a haloalkane, where the alkyl group forms a stable carbocation that reacts with bromide.

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Key Concepts

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

Ether Cleavage

Ether cleavage involves breaking the C-O bond in ethers, typically using strong acids like HBr. The reaction generally produces an alcohol and a haloalkane. The mechanism can vary depending on the structure of the ether, with primary ethers often undergoing SN2 reactions and secondary or tertiary ethers favoring SN1 reactions.

SN1 and SN2 Mechanisms

SN1 and SN2 are two types of nucleophilic substitution reactions. SN1 involves a two-step process with carbocation formation, favoring tertiary carbons, while SN2 is a one-step process with a backside attack, favoring primary carbons. The choice between these mechanisms affects the products formed during ether cleavage.

Stability of Aromatic Compounds

Aromatic compounds, like benzene, are highly stable due to resonance and delocalized π-electrons. This stability makes them less reactive in certain conditions, such as ether cleavage with HBr, where the aromatic ring remains intact, preventing the formation of bromobenzene as a product.

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