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

26. Amines

Amine Alkylation

Organic Chemistry

26. Amines

Amine Alkylation

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3:27 minutes

Problem 6d

Textbook Question

Rank each set of compounds in order of increasing basicity.
(d) pyrrole, imidazole, 3-nitropyrrole

Verified step by step guidance

Step 1: Understand the concept of basicity. Basicity refers to the ability of a compound to donate a lone pair of electrons to accept a proton (H⁺). In organic chemistry, the basicity of nitrogen-containing heterocycles is influenced by factors such as electron density, resonance, and the presence of electron-withdrawing or electron-donating groups.

Step 2: Analyze pyrrole (structure i). Pyrrole has a nitrogen atom with a lone pair of electrons that is delocalized into the aromatic ring system. This delocalization reduces the availability of the lone pair for protonation, making pyrrole less basic.

Step 3: Analyze imidazole (structure ii). Imidazole contains two nitrogen atoms, one of which has a lone pair that is not involved in aromatic delocalization. This lone pair is readily available for protonation, making imidazole more basic than pyrrole.

Step 4: Analyze 3-nitropyrrole (structure iii). The nitro group (-NO₂) is a strong electron-withdrawing group that decreases the electron density on the nitrogen atom in the pyrrole ring. This further reduces the basicity of 3-nitropyrrole compared to pyrrole.

Step 5: Rank the compounds in order of increasing basicity. Based on the analysis, 3-nitropyrrole is the least basic due to the electron-withdrawing nitro group, followed by pyrrole with delocalized lone pair electrons, and imidazole is the most basic due to the availability of a lone pair for protonation.

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Key Concepts

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

Basicity in Organic Chemistry

Basicity refers to the ability of a compound to accept protons (H+) in a chemical reaction. In organic chemistry, basicity is influenced by the availability of lone pairs on nitrogen atoms, which can bond with protons. Compounds with more electron-donating groups tend to be more basic, while those with electron-withdrawing groups are less basic.

Aromaticity and Basicity

Aromatic compounds, such as pyrrole and imidazole, exhibit unique stability due to resonance and delocalization of electrons. This aromatic character can affect basicity; for instance, in pyrrole, the nitrogen's lone pair is involved in the aromatic system, making it less available for protonation compared to imidazole, where the nitrogen's lone pair is more accessible.

Electron-Withdrawing and Electron-Donating Groups

Electron-withdrawing groups (EWGs), like nitro groups (-NO2), decrease basicity by stabilizing the positive charge that forms upon protonation, making it less favorable. Conversely, electron-donating groups (EDGs) enhance basicity by increasing electron density on the nitrogen atom, facilitating protonation. Understanding these effects is crucial for ranking the basicity of the given compounds.

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