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

9. Alkenes and Alkynes

Hydrogenation of Alkynes

Organic Chemistry

9. Alkenes and Alkynes

Hydrogenation of Alkynes

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2:19 minutes

Problem 44c(i)

Textbook Question

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (i) H₂ , Pd/C; If you expect two products, show both.
(c)

Verified step by step guidance

Step 1: Identify the alkyne structure in the given problem. Alkynes are hydrocarbons containing a triple bond between two carbon atoms. The reactivity of the alkyne will depend on whether it is terminal (triple bond at the end of the chain) or internal (triple bond within the chain).

Step 2: Understand the reaction conditions. The problem specifies treatment with H₂ and Pd/C. This is a catalytic hydrogenation reaction, where molecular hydrogen (H₂) is used in the presence of a palladium catalyst supported on carbon (Pd/C). This reaction typically reduces the alkyne completely to an alkane.

Step 3: Predict the mechanism of the reaction. In the presence of Pd/C, the alkyne undergoes successive addition of hydrogen across the triple bond. First, the triple bond is reduced to a double bond (alkene), and then the double bond is further reduced to a single bond (alkane).

Step 4: Determine the product(s). If the alkyne is symmetrical, the reduction will yield a single alkane product. If the alkyne is asymmetrical, the reduction will still yield a single alkane product because the addition of hydrogen is not regioselective under these conditions.

Step 5: If two products are expected, consider stereochemistry or structural variations. However, in this case, catalytic hydrogenation with Pd/C does not typically lead to stereoisomeric products, as the reaction proceeds through a syn-addition mechanism, and the final product is a fully saturated alkane.

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Key Concepts

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

Alkynes

Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond. They are unsaturated compounds and can undergo various reactions, including hydrogenation, where the triple bond is converted into a double or single bond. Understanding the structure and reactivity of alkynes is crucial for predicting the products of their reactions.

Hydrogenation

Hydrogenation is a chemical reaction that involves the addition of hydrogen (H₂) to an unsaturated compound, such as an alkyne or alkene. In the presence of a catalyst like palladium on carbon (Pd/C), alkynes can be converted to alkenes or alkanes. The extent of hydrogenation depends on the reaction conditions and the number of hydrogen molecules added.

Catalysts

Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process. In the context of hydrogenation, palladium on carbon (Pd/C) serves as a catalyst that facilitates the addition of hydrogen to alkynes. Understanding the role of catalysts is essential for predicting reaction pathways and the formation of products.

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Related Practice

Textbook Question

What stereoisomers are obtained from the following reactions?

Textbook Question

What stereoisomers are obtained from the following reactions?

Textbook Question

The following reaction was recently reported to have been performed electrochemically.

(a) Identify the reagent and a solvent that could have been used if this reaction was done traditionally.

(b) What safety and environmental hazards are improved or worsened when doing this reaction electrochemically?

Textbook Question

Show how you would convert

a. oct-3-yne to cis-oct-3-ene.

b. pent-2-yne to trans-pent-2-ene.

Textbook Question

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (ii) H₂, Pd/C, Pb(OAc)₂ , CaCO₃ (Lindlar's catalyst). If you expect two products, show both.

(c)

Textbook Question

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (iii) Na⁰ , NH₃ (liquid), ―33°C . If you expect two products, show both.

(c)

Textbook Question

Predict the product of the following alkyne reductions.

(a)

Textbook Question

Predict the product of the following alkyne reductions.

(b)

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