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

18. Aromaticity

Huckel's Rule

Organic Chemistry

18. Aromaticity

Huckel's Rule

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Multiple Choice

Which of the following molecules is aromatic?

The figure illustrates the structure of a molecule. A 5-membered heterocyclic pentagonal ring is in a horizontal orientation and consists of 1 O, 1 N, and 3 C atoms. O occupies the first position, which is the bottom left vertex. N occupies the third position, which is the top left vertex. A double bond is present between C 1 and N and C 2 and C 3.

The figure illustrates the structure of a molecule. A 6-membered heterocyclic hexagonal ring is in a vertical orientation and consists of 2 N and 4 C atoms. The first N atom bound to H occupies the first position, which is the top right vertex. The second N atom bound to H occupies the second position, which is the bottom right vertex. A double bond is present between C 1 and C 2 and C 3 and C 4.

The figure illustrates the structure of a molecule. A 4-membered heterocyclic square ring is in a horizontal orientation and consists of 1 N and 3 C atoms. N occupies the first position, which is the top left vertex. A double bond is present between N and C 1 and C 2 and C 3.

The figure illustrates the structure of an ion. A 6-membered heterocyclic ring is in a chair conformation and consists of 1 N, 1 O, and 4 C atoms. The N atom occupies the first position, which is the bottom right vertex. N carries a positive charge. The O atom occupies the third position, which is the bottom center vertex. O and C 3 are close to each other. C 4 occupies the top right vertex. A double bond is present between C 1 and C 2 and C 3 and C 4. N is single bonded to C H 3 below and C H 3 on the upper right, each in the form of a line.

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Verified step by step guidance

Identify the criteria for aromaticity: A molecule must be cyclic, planar, fully conjugated, and follow Huckel's rule (4n+2 pi electrons).

Examine the first molecule (oxazole): It is a five-membered ring with alternating double bonds and heteroatoms (N and O) that can contribute lone pairs to the pi system. Count the pi electrons to see if it follows Huckel's rule.

Examine the second molecule (1,2-dihydropyrazine): It is a six-membered ring with two nitrogen atoms. Check if the lone pairs on the nitrogen atoms are part of the conjugated system and count the pi electrons.

Examine the third molecule (azete): It is a four-membered ring with a nitrogen atom. Check if the molecule is planar and if the pi electrons follow Huckel's rule.

Examine the fourth molecule (tropone): It is a seven-membered ring with a positive charge on nitrogen. Check if the molecule is planar, fully conjugated, and if the pi electrons follow Huckel's rule.