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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2:52 minutes

Problem 81

Textbook Question

Ethylene oxide reacts readily with HO^- because of the strain in the three-membered ring. Explain why cyclopropane, a compound with approximately the same amount of strain, does not react with HO^-.

Verified step by step guidance

Understand the structure and reactivity of ethylene oxide: Ethylene oxide is a three-membered cyclic ether (epoxide) with significant ring strain due to its bond angles being much smaller than the ideal tetrahedral angle of 109.5°. This strain makes the molecule highly reactive, especially toward nucleophiles like HO⁻.

Analyze the reaction mechanism of ethylene oxide with HO⁻: The nucleophile (HO⁻) attacks the electrophilic carbon in the epoxide ring, leading to ring opening. This reaction is facilitated by the partial positive charge on the carbon atoms of the epoxide due to the electronegativity of oxygen.

Compare the structure of cyclopropane: Cyclopropane is a three-membered ring hydrocarbon with similar ring strain due to its compressed bond angles. However, unlike ethylene oxide, cyclopropane lacks an electronegative atom like oxygen, which would create an electrophilic site for nucleophilic attack.

Explain the lack of reactivity of cyclopropane with HO⁻: Cyclopropane is composed of only carbon and hydrogen atoms, which are nonpolar and do not provide an electrophilic site for the nucleophile (HO⁻) to attack. The absence of a polar bond or partial charges in cyclopropane makes it inert to nucleophilic attack under normal conditions.

Conclude the reasoning: The key difference lies in the presence of an electrophilic site in ethylene oxide due to the oxygen atom, which facilitates nucleophilic attack and ring opening. Cyclopropane, despite having similar ring strain, does not have such a site, and therefore does not react with HO⁻.

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Key Concepts

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

Ring Strain

Ring strain occurs in cyclic compounds when the bond angles deviate from the ideal tetrahedral angle of 109.5 degrees, leading to increased energy and reactivity. In ethylene oxide, the three-membered ring creates significant angle strain, making it more reactive towards nucleophiles like HO-. Cyclopropane also has ring strain, but its stability is enhanced by the ability to adopt a more favorable conformation.

Nucleophilic Attack

Nucleophilic attack involves a nucleophile, such as HO-, attacking an electrophilic center in a molecule. Ethylene oxide's strained ring makes the carbon atoms more electrophilic, facilitating this reaction. In contrast, cyclopropane lacks such electrophilic centers due to its stable structure, making it less susceptible to nucleophilic attack despite having similar strain.

Stability of Cyclopropane

Cyclopropane is relatively stable due to its ability to maintain a planar structure, which minimizes torsional strain. This stability results in lower reactivity compared to ethylene oxide, where the strain leads to a higher energy state. Consequently, cyclopropane does not readily undergo reactions with nucleophiles like HO-, as it does not have the same driving force for reaction as ethylene oxide.

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