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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2:57 minutes

Problem 22a

Textbook Question

Predict the product of the following hydrogenation reactions.
(a)

Verified step by step guidance

Identify the type of compound undergoing hydrogenation. Typically, hydrogenation reactions involve alkenes, alkynes, or aromatic compounds reacting with hydrogen (H₂) in the presence of a catalyst such as Pd, Pt, or Ni.

Determine the functional group that will be affected by the hydrogenation. For example, in alkenes, the π-bond of the double bond will be reduced to a single bond, and in alkynes, the triple bond will be reduced to a double bond or a single bond depending on the reaction conditions.

Write the balanced chemical equation for the reaction. For example, if the starting material is an alkene, add H₂ across the double bond to form the corresponding alkane.

Consider the stereochemistry of the product. In catalytic hydrogenation, the addition of hydrogen is typically syn (both hydrogens add to the same face of the molecule). If the starting material is cyclic, this can lead to specific stereoisomers.

Draw the structure of the product, ensuring that all π-bonds in the affected functional group have been reduced and that the correct stereochemistry is represented if applicable.

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Key Concepts

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

Hydrogenation

Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to an unsaturated compound, typically an alkene or alkyne, converting it into a saturated compound. This process is commonly facilitated by catalysts such as palladium, platinum, or nickel, which help lower the activation energy required for the reaction. Understanding hydrogenation is crucial for predicting the products of reactions involving double or triple bonds.

Saturation and Unsaturation

In organic chemistry, saturation refers to the presence of single bonds between carbon atoms, while unsaturation indicates the presence of double or triple bonds. Saturated compounds, like alkanes, have the maximum number of hydrogen atoms, whereas unsaturated compounds, like alkenes and alkynes, have fewer hydrogen atoms due to the presence of multiple bonds. Recognizing the degree of saturation is essential for predicting the outcome of hydrogenation reactions.

Reaction Mechanism

The reaction mechanism describes the step-by-step process by which reactants are converted into products in a chemical reaction. In hydrogenation, the mechanism typically involves the adsorption of hydrogen and the unsaturated compound onto the catalyst's surface, followed by the breaking of bonds and the formation of new bonds. Understanding the mechanism helps in predicting the specific products formed during the reaction and the conditions that may influence the reaction pathway.

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