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

27. Heterocycles

Acid-Base Properties of Nitrogen Heterocycles

Organic Chemistry

27. Heterocycles

Acid-Base Properties of Nitrogen Heterocycles

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Multiple Choice

Rank following heterocycles in order of increasing basicity.

B < A < D < C

C < D < B < A

D < B < C < A

D < C < B < A

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Verified step by step guidance

Identify the heterocycles: A is pyrrolidine, B is imidazole, C is imidazolium ion, and D is indole.

Understand basicity: Basicity in nitrogen-containing heterocycles is influenced by the availability of the lone pair of electrons on the nitrogen atom to accept a proton.

Analyze structure A (pyrrolidine): It is a saturated five-membered ring with a nitrogen atom. The nitrogen's lone pair is not involved in resonance, making it more available for protonation, thus more basic.

Analyze structure B (imidazole): It is an aromatic five-membered ring with two nitrogen atoms. One nitrogen's lone pair is involved in the aromatic sextet, while the other is available for protonation, making it less basic than pyrrolidine but more basic than imidazolium.

Analyze structure C (imidazolium ion): It is a protonated form of imidazole, carrying a positive charge. The positive charge reduces the availability of the nitrogen's lone pair for further protonation, making it less basic than imidazole.

Analyze structure D (indole): It is a bicyclic structure with a pyrrole ring fused to a benzene ring. The nitrogen's lone pair is involved in the aromatic sextet, making it less available for protonation, thus the least basic among the given heterocycles.

Rank the basicity: Based on the analysis, the order of increasing basicity is D < C < B < A.