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

Naming Epoxides

Organic Chemistry

12. Alcohols, Ethers, Epoxides and Thiols

Naming Epoxides

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3:29 minutes

Problem 60a,b

Textbook Question

What is the major product obtained from the reaction of 2-ethyloxirane with each of the following reagents?
a. 0.1MHCl
b. CH₃OH/HCl

Verified step by step guidance

Step 1: Understand the structure of 2-ethyloxirane. It is an epoxide, which is a three-membered cyclic ether. The ring is highly strained, making it reactive towards nucleophiles and acids.

Step 2: For part (a), when 2-ethyloxirane reacts with 0.1M HCl, the reaction proceeds via acid-catalyzed ring opening. The proton (H⁺) from HCl protonates the oxygen atom of the epoxide, increasing the electrophilicity of the carbon atoms in the ring.

Step 3: After protonation, the nucleophilic chloride ion (Cl⁻) attacks the more substituted carbon of the epoxide ring (following Markovnikov's rule), leading to the formation of a halohydrin. This step involves a regioselective ring-opening mechanism.

Step 4: For part (b), when 2-ethyloxirane reacts with CH₃OH in the presence of HCl, the reaction also proceeds via acid-catalyzed ring opening. The oxygen atom of the epoxide is protonated by H⁺, making the ring more susceptible to nucleophilic attack.

Step 5: The nucleophile in this case is methanol (CH₃OH). Methanol attacks the more substituted carbon of the epoxide ring (again following Markovnikov's rule), leading to the formation of a β-methoxy alcohol as the major product.

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Key Concepts

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

Epoxide Reactivity

Epoxides, or oxiranes, are three-membered cyclic ethers that are highly reactive due to the strain in their ring structure. This strain makes them susceptible to nucleophilic attack, allowing them to undergo ring-opening reactions. The nature of the nucleophile and the reaction conditions can significantly influence the outcome of the reaction, leading to different products.

Acid-Catalyzed Ring Opening

In the presence of an acid, such as HCl, epoxides can undergo ring-opening through protonation of the oxygen atom, which increases the electrophilicity of the carbon atoms in the epoxide. This process typically leads to the formation of a more stable carbocation intermediate, allowing for nucleophiles to attack and open the ring, resulting in the formation of alcohols or other functional groups.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group by a nucleophile. In the context of the reaction with 2-ethyloxirane, the nucleophile (like CH3OH in the presence of HCl) attacks the more substituted carbon of the epoxide after the ring has been opened, leading to the formation of a product that retains the original carbon skeleton while introducing new functional groups.

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