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

Aromaticity

Organic Chemistry

18. Aromaticity

Aromaticity

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Problem 8

Textbook Question

If Kekulé's original hypothesis had been correct and benzene was really an equilibrium between two structures, how many distinct isomers would exist for 1,2-dichlorobenzene?

Verified step by step guidance

Understand Kekulé's original hypothesis: Kekulé proposed that benzene is an equilibrium between two cyclohexatriene structures, where the double bonds alternate positions.

Consider the structure of 1,2-dichlorobenzene: In the given structure, two chlorine atoms are attached to adjacent carbon atoms in the benzene ring.

Analyze the effect of Kekulé's hypothesis: If benzene were an equilibrium between two structures, the position of the double bonds would change, potentially affecting the relative positions of substituents.

Determine the possible isomers: With alternating double bonds, the positions of the chlorine atoms could lead to different isomers depending on which double bond configuration is present at any given time.

Count the distinct isomers: Consider the different possible arrangements of the chlorine atoms with respect to the alternating double bonds to determine the number of distinct isomers.

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Key Concepts

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

Kekulé Structure of Benzene

Friedrich August Kekulé proposed that benzene is a cyclic compound with alternating single and double bonds, leading to resonance structures. This model suggests that benzene can be represented as an equilibrium between two distinct structures, which influences the understanding of its reactivity and isomerism.

Isomerism in Organic Chemistry

Isomerism refers to the phenomenon where compounds have the same molecular formula but different structural arrangements. In the case of 1,2-dichlorobenzene, the presence of two chlorine atoms on the benzene ring can lead to different spatial arrangements, resulting in distinct isomers such as ortho, meta, and para configurations.

Ortho, Meta, and Para Substitution

In aromatic compounds, substitution patterns are categorized as ortho (adjacent positions), meta (one carbon apart), and para (opposite positions). For 1,2-dichlorobenzene, the ortho isomer has both chlorines on adjacent carbons, while the para isomer has them on opposite sides, illustrating how substitution affects the properties and classification of isomers.

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Related Practice

Textbook Question

Using the information in Figure 16-2, calculate the values of ∆H° for the following reactions:

(c)

Multiple Choice

How does ΔH°_hydr of an aromatic molecule compare to an otherwise identical sample of an analogous nonconjugated molecule?

Textbook Question

Does the MO energy diagram of cyclooctatetraene (Figure 16-8) appear to be a particularly stable or unstable configuration? Explain.

Textbook Question

Molecule A is significantly more water soluble than molecule B. Justify this observation.

Textbook Question

a. Draw the resonance forms of benzene, cyclobutadiene, and cyclooctatetraene, showing all the carbon and hydrogen atoms.

b. Assuming that these molecules are all planar, show how the p orbitals on the sp2 hybrid carbon atoms form continuous rings of overlapping orbitals above and below the plane of the carbon atoms.

Textbook Question

Using the information in Figure 16-2, calculate the values of ∆H° for the following reactions:

(a)

Textbook Question

Using the information in Figure 16-2, calculate the values of ∆H° for the following reactions:

(b)

Textbook Question

Using the information in Figure 16-2, calculate the values of ∆H° for the following reactions:

(c)

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