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

3. Acids and Bases

Ranking Acidity

Organic Chemistry

3. Acids and Bases

Ranking Acidity

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4:02 minutes

Problem 32

Textbook Question

Explain why the C-3 OH group of vitamin C is more acidic than the C-2 OH group.

Verified step by step guidance

Identify the structure of vitamin C (ascorbic acid) from the image. It contains a six-membered ring with hydroxyl groups at positions C-2, C-3, and C-5, along with a lactone group at C-1 and a double bond between C-2 and C-3.

Understand the concept of acidity in organic molecules. Acidity is influenced by the ability of the molecule to stabilize the negative charge on the conjugate base after deprotonation. This stabilization can occur through resonance, inductive effects, or hydrogen bonding.

Analyze the C-3 OH group. When the proton is removed from the C-3 OH group, the resulting conjugate base can delocalize the negative charge through resonance with the adjacent double bond between C-2 and C-3. This resonance stabilization makes the C-3 OH group more acidic.

Compare the C-2 OH group. When the proton is removed from the C-2 OH group, the resulting conjugate base does not benefit from resonance stabilization because the negative charge cannot delocalize effectively into the ring system. This makes the C-2 OH group less acidic.

Conclude that the C-3 OH group is more acidic than the C-2 OH group due to the resonance stabilization of its conjugate base, which is not available for the C-2 OH group.

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Key Concepts

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

Acidity and pKa

Acidity in organic chemistry refers to the tendency of a compound to donate a proton (H+). The strength of an acid is often measured by its pKa value; lower pKa values indicate stronger acids. In the context of vitamin C, the C-3 OH group is more acidic than the C-2 OH group, which can be attributed to the stability of the resulting conjugate base after deprotonation.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. In vitamin C, the conjugate base formed from the C-3 OH group can be stabilized by resonance with the adjacent carbonyl group, making it more favorable for the C-3 OH group to lose a proton compared to the C-2 OH group, which lacks similar stabilization.

Inductive Effect

The inductive effect refers to the electron-withdrawing or electron-donating effects of substituents on a molecule, influencing acidity. In vitamin C, the presence of electronegative atoms or groups near the C-3 OH group can enhance its acidity by stabilizing the negative charge on the conjugate base through inductive withdrawal of electron density, further contributing to the greater acidity of the C-3 OH group compared to the C-2 OH group.

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