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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Problem 80a

Textbook Question

Predict the product of the following epoxide addition reactions.
(a)

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Identify the functional groups in the reactant. The molecule contains an epoxide (a three-membered cyclic ether) and a silyl ether group (Si-O bond). The reaction involves the use of sodium ethoxide (NaOEt) in ethanol (EtOH), which is a strong nucleophile and base.

Understand the reactivity of the epoxide. Epoxides are highly strained and reactive towards nucleophiles. Under basic conditions, the nucleophile (ethoxide ion, EtO⁻) will attack the less sterically hindered carbon of the epoxide ring, leading to ring opening.

Determine the stereochemical outcome of the nucleophilic attack. The attack of the nucleophile occurs in an SN2-like manner, resulting in inversion of configuration at the carbon being attacked. In this case, the nucleophile will attack the carbon bearing the hydrogen atom (less sterically hindered).

Predict the product of the reaction. The ethoxide ion will add to the less hindered carbon of the epoxide, and the oxygen from the epoxide will remain attached to the other carbon. The stereochemistry at the attacked carbon will invert due to the backside attack.

Consider the stability of the silyl ether group. The silyl ether group (Si-O bond) is not reactive under these conditions and will remain intact in the product. The final product will be a molecule with an opened epoxide ring, an ethoxy group attached to the less hindered carbon, and the silyl ether group unchanged.

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Key Concepts

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

Epoxide Structure

Epoxides are three-membered cyclic ethers characterized by a highly strained ring structure. This strain makes them reactive intermediates in organic reactions. The oxygen atom in the epoxide contributes to the ring's reactivity, allowing for nucleophilic attack at the carbon atoms adjacent to the oxygen.

Nucleophilic Attack

Nucleophilic attack is a fundamental reaction mechanism in organic chemistry where a nucleophile donates an electron pair to an electrophile, forming a new bond. In the case of epoxide reactions, nucleophiles can open the epoxide ring by attacking one of the carbon atoms, leading to the formation of diols or other products depending on the conditions and nucleophile used.

Regioselectivity and Stereochemistry

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others, while stereochemistry involves the spatial arrangement of atoms in molecules. In epoxide addition reactions, the choice of nucleophile and reaction conditions can influence which carbon atom is attacked and the stereochemical outcome, resulting in specific configurations of the product.

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Related Practice

Textbook Question

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

(a) NaOCH₂CH₃ (sodium ethoxide)

(b) NaNH₂ (sodium amide)

Textbook Question

Predict the products of the following reactions.

(m)

(n)

Textbook Question

Working backward, design a synthesis of the following alcohol using two different epoxide/Grignard reagent combinations.

Textbook Question

Predict the product of the following epoxide addition reactions.

(b)

Textbook Question

In Chapter 13, we learned that epoxide opening can give different products, depending on whether the reaction occurs under acidic or basic conditions. Explain why the epoxide shown opens identically under either set of conditions.

Textbook Question

In Chapter 13, we discuss the ring-opening reactions of epoxides, such as the one shown here.

(a) Based on the bonds formed and the bonds broken, calculate ∆H°.

Textbook Question

Chapter 8 discussed the synthesis of cholesterol, which proceeds by a cationic cyclization cascade. Without looking back, suggest a mechanism by which the following reaction occurs. [The carbons have been numbered for you.]

Textbook Question

Despite it being equally favorable, opening of the epoxide does not happen in the absence of an acid catalyst. How does acid make the reaction faster? Demonstrate this concept by directly comparing the reaction coordinate diagram for both situations A and B.

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Predict the product of the following epoxide addition reactions.(a)

Key Concepts

Epoxide Structure

Nucleophilic Attack

Regioselectivity and Stereochemistry

Watch next

Predict the product of the following epoxide addition reactions.
(a)