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

10. Addition Reactions

Hydrogenation

Organic Chemistry

10. Addition Reactions

Hydrogenation

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4:34 minutes

Problem 50

Textbook Question

On a per alkene basis, which would have the more negative heat of hydrogenation?

Verified step by step guidance

Understand the concept of heat of hydrogenation: It is the heat released when an alkene is converted to an alkane by the addition of hydrogen. A more negative heat of hydrogenation indicates a less stable alkene.

Identify the factors affecting alkene stability: More substituted alkenes (those with more alkyl groups attached to the double-bonded carbons) are generally more stable due to hyperconjugation and inductive effects.

Compare the degree of substitution: Determine the number of alkyl groups attached to the double-bonded carbons in each alkene. The alkene with fewer substituents will typically have a more negative heat of hydrogenation.

Consider the presence of any additional stabilizing or destabilizing factors: Look for conjugation with other double bonds or aromatic rings, which can stabilize the alkene, or steric hindrance, which can destabilize it.

Evaluate the alkenes based on these criteria: The alkene with the least stability (fewest substituents and least conjugation) will have the more negative heat of hydrogenation.

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Key Concepts

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

Heat of Hydrogenation

The heat of hydrogenation is the amount of energy released when an alkene undergoes hydrogenation, converting into an alkane. It is a measure of the stability of the alkene; more stable alkenes have less negative heats of hydrogenation because they release less energy upon hydrogenation. This concept helps compare the relative stabilities of different alkenes.

Alkene Stability

Alkene stability is influenced by factors such as the degree of substitution and the presence of electron-donating or withdrawing groups. More substituted alkenes are generally more stable due to hyperconjugation and the inductive effect, which stabilize the double bond. Understanding these factors is crucial for predicting which alkene will have a more negative heat of hydrogenation.

Substitution Patterns in Alkenes

Substitution patterns refer to the number and type of groups attached to the carbon atoms of the double bond in an alkene. Tetrasubstituted alkenes are more stable than trisubstituted, disubstituted, and monosubstituted alkenes. This hierarchy is important because more substituted alkenes tend to have less negative heats of hydrogenation, indicating greater stability.

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Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H₂, Pd/C

(k)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (x) D₂ , Pd/C.

(k)

Textbook Question

At the beginning of Chapter 9, we stated that after finishing Chapters 8 and 9, we would have the ability to make a large variety of functional groups using related reactions. Show the reagent(s) necessary to convert 1-isobutylcyclohexene into the following molecules.

(e)

Textbook Question

The chiral catalyst (R)-BINAP(COD)RhOTf was used in a hydrogenation reaction as part of the synthesis of fragment C of indinavir. Using the same alkene, predict the product that would be obtained if (S)-BINAP(COD)RhOTf were used instead.

Textbook Question

Identify the product when each of the following reactions is performed on the triglyceride of linoleic acid (linoleate).

(b) H₂ , Ni (partial hydrogenation)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H₂, Pd/C; and (x) D₂ , Pd/C.

(e)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H₂, Pd/C; and (x) D₂, Pd/C.

(l)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br₂ (ii) Cl₂

(l)

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