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 25

Textbook Question

Explain why methyl propyl ether forms both methyl iodide and propyl iodide when it is heated with excess HI.

Verified step by step guidance

When methyl propyl ether (CH₃OCH₂CH₂CH₃) is heated with excess HI, the reaction proceeds via an acid-catalyzed cleavage of the ether bond. The first step involves the protonation of the ether oxygen by HI, forming an oxonium ion (R-O⁺-R').

The oxonium ion is unstable and undergoes cleavage to form two products: a methyl group (CH₃⁺) and a propyl group (CH₂CH₂CH₃⁺). This cleavage occurs because ethers are susceptible to nucleophilic attack after protonation.

The iodide ion (I⁻) from HI acts as a nucleophile and attacks the carbocation formed during the cleavage. Depending on which bond breaks, either methyl iodide (CH₃I) or propyl iodide (CH₃CH₂CH₂I) is formed.

The cleavage of the ether bond is influenced by the stability of the carbocation intermediates. In this case, both methyl and propyl carbocations can form, but the reaction proceeds with both pathways due to the excess HI present.

As a result, both methyl iodide and propyl iodide are formed as products of the reaction, with the iodide ion reacting with each carbocation formed during the cleavage of the ether bond.

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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 is a reaction where ethers are broken down into their corresponding alcohols and alkyl halides in the presence of strong acids, such as HI. In this process, the ether bond (C-O) is cleaved, leading to the formation of two alkyl halides. This reaction is significant in organic chemistry as it demonstrates how ethers can be transformed into more reactive species.

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile replaces a leaving group in a molecule. In the case of methyl propyl ether reacting with HI, the iodide ion (I-) acts as a nucleophile, attacking the carbon atoms bonded to the ether oxygen, resulting in the formation of methyl iodide and propyl iodide. Understanding this mechanism is crucial for predicting the products of ether cleavage.

Reactivity of Alkyl Halides

The reactivity of alkyl halides is influenced by the structure of the carbon atom to which the halide is attached. Methyl and primary alkyl halides, like those formed from methyl propyl ether, are generally more reactive towards nucleophiles due to less steric hindrance. This reactivity is essential in understanding why both methyl iodide and propyl iodide are produced when the ether is heated with excess HI.

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