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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Problem 62b

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.
(b)

Verified step by step guidance

Step 1: Understand the structure of isoprene units. Isoprene is a 5-carbon molecule with the formula C₅H₈, consisting of two double bonds. In terpenes, isoprene units are linked together in various ways, often through C₁-C₄ linkages, but other linkages are possible.

Step 2: Analyze the structure of farnesol provided in the image. Farnesol is a sesquiterpene, meaning it is composed of three isoprene units. Look for repeating patterns of 5-carbon units within the molecule.

Step 3: Identify the isoprene units in farnesol. Start by locating the double bonds and methyl groups, which are characteristic features of isoprene units. Divide the molecule into three distinct 5-carbon segments based on these features.

Step 4: Note the linkages between the isoprene units. In farnesol, the isoprene units are connected in a head-to-tail fashion, meaning the C₁ of one isoprene unit is linked to the C₄ of the next. Observe any deviations from this pattern, such as cross-linking or ring formation.

Step 5: Highlight the functional group present in farnesol. The hydroxyl (-OH) group at the end of the molecule is an important feature that distinguishes farnesol from other terpenes. This group does not affect the identification of isoprene units but is relevant for understanding the molecule's reactivity and properties.

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Key Concepts

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

Isoprene Units

Isoprene units are the fundamental building blocks of terpenes, consisting of a five-carbon structure with the formula C₅H₈. These units can polymerize to form larger molecules, and in terpenes, they typically connect in a head-to-tail fashion. Understanding how these units combine is crucial for identifying the structure of various terpenes.

Terpene Structure

Terpenes are a diverse class of organic compounds produced by many plants, characterized by their strong odors and roles in plant defense. They are classified based on the number of isoprene units they contain, such as monoterpenes (two units) and sesquiterpenes (three units). Recognizing the structural variations, including rings and cross-linkages, is essential for analyzing their chemical properties.

Linkages in Terpenes

In terpenes, linkages can occur not only between the C₁ and C₄ positions of isoprene units but also at other carbon positions, especially in cyclic or cross-linked structures. This flexibility in bonding leads to a variety of structural forms and functional properties. Understanding these linkages is vital for accurately identifying and classifying different terpenes.

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Related Practice

Textbook Question

a. How many MOs does 1,3,5,7-octatetraene have?

b. What is the designation of its HOMO (c1, c2, etc.)?

c. How many nodes does its highest energy MO have between the nuclei?

Textbook Question

Why is this not a viable representation of the ψ₂, molecular orbital of buta-1,3-diene?

Textbook Question

The ψ₂ molecular orbital for octa-1,3,5,7-tetraene is shown. Draw ψ₃.

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Textbook Question

Hexa-1,3,5-triene uses six p orbitals, each containing a single electron, to make its three π bonds. How many total molecular orbitals are made by the six p orbitals?

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.

(c)

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.

(e)

Textbook Question

Vitamin E, especially the B ring and the side chain, is a terpenoid derivative. Identify the isoprene units nature used to make it.

Textbook Question

For the following terpenes, identify the isoprene units. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C₁ and C₄ of isoprene.

(a)

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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.(b)

Key Concepts

Isoprene Units

Terpene Structure

Linkages in Terpenes

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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.
(b)