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

Alcohol Nomenclature

Organic Chemistry

12. Alcohols, Ethers, Epoxides and Thiols

Alcohol Nomenclature

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4:39 minutes

Problem 39

Textbook Question

Propose a mechanism for proton exchange of an alcohol in aqueous base.

Verified step by step guidance

Identify the functional group in the alcohol molecule. The alcohol group (-OH) contains a hydroxyl group, which can act as both a weak acid and a weak base depending on the reaction conditions.

Recognize the role of the aqueous base. Aqueous base (e.g., hydroxide ion, OH⁻) can deprotonate the alcohol by abstracting the proton (H⁺) from the hydroxyl group.

Write the first step of the mechanism: The hydroxide ion (OH⁻) attacks the hydrogen atom of the hydroxyl group in the alcohol, forming water (H₂O) as a byproduct. This step can be represented as:

R_{-} (OH) + {OH}_{-} \to R_{-} (O -) + H O_{-} H

Explain the formation of the alkoxide ion: After the proton is removed, the alcohol is converted into an alkoxide ion (R-O⁻), which is a stronger base than the original alcohol. This is a key intermediate in the mechanism.

Conclude the mechanism: The proton exchange is complete when the hydroxide ion abstracts the proton, leaving behind the alkoxide ion and water. This equilibrium process is reversible, and the position of equilibrium depends on the pKa values of the alcohol and water.

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Key Concepts

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

Proton Exchange Mechanism

Proton exchange mechanisms involve the transfer of protons (H+) between molecules, which is crucial in acid-base reactions. In the context of alcohols, this process typically occurs when an alcohol donates a proton to a base, resulting in the formation of an alkoxide ion. Understanding this mechanism is essential for predicting the behavior of alcohols in aqueous solutions.

Role of Aqueous Base

An aqueous base, such as sodium hydroxide (NaOH), provides hydroxide ions (OH-) that can interact with alcohols. The presence of a base facilitates the deprotonation of the alcohol, leading to the formation of an alkoxide ion. This interaction is a key step in the proton exchange mechanism, as it drives the equilibrium towards the formation of the deprotonated species.

Equilibrium in Acid-Base Reactions

Acid-base reactions often reach a state of equilibrium, where the rates of the forward and reverse reactions are equal. In the case of alcohols in aqueous base, the equilibrium will favor the formation of the alkoxide ion and water. Understanding this concept helps in predicting the extent of proton exchange and the stability of the resulting species in solution.