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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1:31 minutes

Problem 22b

Textbook Question

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

Verified step by step guidance

Identify the type of compound undergoing hydrogenation. Hydrogenation typically involves the addition of hydrogen (H₂) to unsaturated compounds, such as alkenes or alkynes, in the presence of a catalyst (e.g., Pd, Pt, or Ni).

Determine the structure of the starting material. If the compound contains a double bond (alkene) or triple bond (alkyne), these unsaturated bonds will be reduced to single bonds (alkane) during hydrogenation.

Write the balanced chemical equation for the reaction. For example, if the starting material is an alkene (C=C), the addition of H₂ will convert it to an alkane (C-C). Use MathML to represent the reaction:

R - CH = CH - R' + H_{2} \to R - CH - CH - R'

Consider the stereochemistry of the product. In catalytic hydrogenation, the addition of hydrogen occurs on the same face of the double bond (syn addition), leading to a specific stereochemical outcome if the starting material is cyclic or has substituents.

Draw the final product, ensuring that all double or triple bonds in the starting material have been fully reduced to single bonds, and verify that the molecular formula and stereochemistry are consistent with the reaction conditions.

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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 often facilitated by a catalyst, such as palladium, platinum, or nickel, which lowers the activation energy required for the reaction. Understanding hydrogenation is crucial for predicting the products of reactions involving double or triple bonds.

Stereochemistry

Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In hydrogenation reactions, the stereochemistry of the starting material can influence the configuration of the product, leading to different isomers. Recognizing whether the reaction leads to cis or trans products is essential for accurately predicting the outcome of hydrogenation.

Reaction Mechanism

A reaction mechanism is a step-by-step description of the process by which reactants are converted into products. In the case of hydrogenation, the mechanism typically involves the adsorption of the alkene onto the catalyst surface, followed by the addition of hydrogen atoms to the carbon atoms of the double bond. Understanding the mechanism helps in predicting the specific products formed and the conditions under which the reaction occurs.