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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5:09 minutes

Problem 18a,b

Textbook Question

Which member of each pair is the stronger base?
a. ethylamine or aniline
b. ethylamine or ethoxide ion

Verified step by step guidance

Step 1: Analyze the chemical structures in part (a). Ethylamine (ii) is an aliphatic amine, while aniline (i) is an aromatic amine. The lone pair on the nitrogen in aniline is delocalized into the aromatic ring, reducing its availability to accept protons. In contrast, the lone pair on the nitrogen in ethylamine is localized and readily available for protonation, making ethylamine a stronger base.

Step 2: Compare the chemical structures in part (b). Ethylamine (i) is a neutral amine, while ethoxide ion (ii) is an alkoxide ion with a negative charge. The negative charge on the ethoxide ion makes it more nucleophilic and a stronger base compared to the neutral ethylamine. Bases with negative charges are generally stronger than their neutral counterparts.

Step 3: Consider the role of resonance in part (a). The delocalization of the nitrogen's lone pair in aniline decreases its basicity because resonance stabilizes the molecule, making it less likely to donate electrons. Ethylamine lacks resonance stabilization, which increases its basicity.

Step 4: Evaluate the inductive effects in part (b). The ethoxide ion has a strong electron-donating effect due to its negative charge, which enhances its ability to act as a base. Ethylamine, being neutral, does not have this additional electron density, making it a weaker base in comparison.

Step 5: Summarize the findings. In part (a), ethylamine is the stronger base due to the lack of resonance stabilization. In part (b), ethoxide ion is the stronger base due to its negative charge and higher electron density.

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Key Concepts

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

Basicity and Electron Density

Basicity refers to the ability of a compound to accept protons (H+). The strength of a base is influenced by the electron density on the atom that donates the lone pair. In amines, the presence of electron-donating groups increases electron density, enhancing basicity, while electron-withdrawing groups decrease it.

Aromaticity and Resonance

Aromatic compounds, like aniline, exhibit resonance stabilization, where the lone pair on the nitrogen can delocalize into the aromatic ring. This delocalization reduces the availability of the lone pair for protonation, making aniline a weaker base compared to aliphatic amines like ethylamine, which lack such resonance effects.

Comparison of Alkoxide and Amine Bases

Alkoxide ions (e.g., ethoxide) are generally stronger bases than amines due to their negative charge and the absence of resonance stabilization. The alkoxide's oxygen atom has a high electron density, making it more eager to accept protons compared to the nitrogen in amines, which may have resonance effects that stabilize the lone pair.

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