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

16. Conjugated Systems

Conjugation Chemistry

Organic Chemistry

16. Conjugated Systems

Conjugation Chemistry

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3:43 minutes

Problem 62a

Textbook Question

Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C₁ and C₄ of isoprene.
(a)

Verified step by step guidance

Step 1: Recall the structure of an isoprene unit. Isoprene is a 5-carbon molecule with the formula C₅H₈, consisting of two double bonds. Its structure can be represented as CH₂=C(CH₃)-CH=CH₂.

Step 2: Understand the concept of terpenes. Terpenes are composed of repeating isoprene units, which are joined together in specific patterns. The connection between isoprene units can occur at various positions, not just C₁ and C₄.

Step 3: Examine the structure of the given terpene. Look for repeating patterns of 5-carbon units that resemble the isoprene structure. Pay attention to any cross-linking or ring formations that may alter the typical linear arrangement.

Step 4: Identify the isoprene units within the terpene structure. Break down the molecule into segments of 5-carbon units and determine how they are connected. Highlight any deviations from the standard C₁-C₄ linkage.

Step 5: Verify your identification by ensuring that each segment matches the molecular formula and structural characteristics of an isoprene unit. Consider how the linkages or rings affect the overall structure of the terpene.

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Key Concepts

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

Isoprene Structure

Isoprene is a five-carbon diene (C₅H₈) with the structure CH₂=C(CH₃)-CH=CH₂. It serves as the fundamental building block for terpenes, which are organic compounds produced by various plants. Understanding the isoprene structure is crucial for identifying how these units combine to form larger, more complex molecules in terpenes.

Terpene Classification

Terpenes are classified based on the number of isoprene units they contain. Monoterpenes consist of two isoprene units, sesquiterpenes have three, and so on. This classification helps in understanding the diversity of terpenes and their structural variations, including linear and cyclic forms, which are essential for identifying specific terpenes in the question.

Cross-Linking in Terpenes

Cross-linking in terpenes refers to the formation of bonds between isoprene units that do not follow the typical C₁ to C₄ linkage. This can lead to the creation of complex structures such as rings or branched chains. Recognizing these alternative linkages is vital for accurately identifying the isoprene units in more intricate terpenes, especially in cyclic or cross-linked forms.

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Related Practice

Textbook Question

Answer the following questions for the molecular orbitals (MOs) of 1,3,5,7-octatetraene:

b. Which are the bonding MOs, and which are the antibonding MOs?

Textbook Question

Answer the following questions for the molecular orbitals (MOs) of 1,3,5,7-octatetraene:

f. What is the relationship between HOMO and LUMO and symmetric and antisymmetric orbitals?

Textbook Question

Classify the following dienes and polyenes as isolated, conjugated, cumulated, or some combination of these classifications.

(a) cycloocta-1,4-diene

(b) cycloocta-1,3-diene

(d) cycloocta-1,3,5,7-tetraene

(e) cyclohexa-1,3,5-triene (benzene)

(f) penta-1,2,4-triene

Textbook Question

How many 𝝅 electrons are involved in the conjugated system for each of the following molecules?

(a)

Textbook Question

Phenolphthalein is an acid–base indicator that is colorless below pH 8 and red above pH 8. Explain briefly why the first structure is colorless and the second structure is colored.

Textbook Question

Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.

(g)

Textbook Question

Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.

(h)

Textbook Question

Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.

(i)

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Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C1 and C4 of isoprene.(a)

Key Concepts

Isoprene Structure

Terpene Classification

Cross-Linking in Terpenes

Watch next

Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C₁ and C₄ of isoprene.
(a)