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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6:17 minutes

Problem 25a,b

Textbook Question

How many different alkenes can be hydrogenated to form
a. butane?
b. 3-methylpentane?

Verified step by step guidance

Identify the molecular formula of the target alkane. For butane, the molecular formula is C₄H₁₀, and for 3-methylpentane, the molecular formula is C₆H₁₄.

Recall that alkenes are unsaturated hydrocarbons containing at least one double bond. Hydrogenation of an alkene adds H₂ across the double bond, converting it into a saturated alkane.

For part (a), determine all possible alkenes with the molecular formula C₄H₈. Consider different structural isomers, including straight-chain and branched alkenes, as well as positional isomers of the double bond.

For part (b), determine all possible alkenes with the molecular formula C₆H₁₂ that can be hydrogenated to form 3-methylpentane. Focus on structural isomers where the double bond is positioned in a way that hydrogenation results in the correct branching pattern of 3-methylpentane.

Count the total number of unique alkenes for each part, ensuring that stereoisomers (cis/trans or E/Z) are also considered where applicable, as they represent distinct alkenes.

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Key Concepts

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

Alkenes

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). They are unsaturated compounds, meaning they have fewer hydrogen atoms than alkanes, which are saturated. The presence of the double bond allows alkenes to undergo various chemical reactions, including hydrogenation, where hydrogen is added across the double bond to form alkanes.

Hydrogenation

Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to an unsaturated compound, such as an alkene, to convert it into a saturated compound, typically an alkane. This reaction is often facilitated by catalysts, such as platinum, palladium, or nickel, and is significant in organic chemistry for modifying the structure and properties of organic molecules.

Structural Isomers

Structural isomers are compounds that have the same molecular formula but differ in the arrangement of atoms. In the context of alkenes, different structural isomers can lead to various alkenes that can be hydrogenated to yield the same alkane. Understanding structural isomerism is crucial for determining how many distinct alkenes can produce a specific alkane upon hydrogenation.

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Related Practice

Textbook Question

Draw the products of the following reactions. If the products can exist as stereoisomers, show which stereoisomers are formed

f. 1,2-dideuteriocyclohexene + H₂, Pd/C

Textbook Question

Draw the products of the following reactions. If the products can exist as stereoisomers show what stereoisomers are formed.

k. (Z)-3,4-dimethyl-3-hexene + H₂, Pd/C

l. (E)-3,4-dimethyl-3-hexene + H₂, Pd/C

Textbook Question

Using any alkene and any other reagents, how would you prepare the following compounds?

Textbook Question

Draw the structure of a compound with molecular C₈H₁₄ that reacts with one equivalent of H₂ over Pd/C to form a meso compound

Textbook Question

What alkene would you start with if you wanted to synthesize

a. pentane?

Textbook Question

Draw the products of the following reactions. If the products can exist as stereoisomers, show which stereoisomers are formed.

i. (Z)-3,4-dimethyl-3-heptene + H₂, Pd/C

Textbook Question

What stereoisomers would you expect to obtain from each of the following reactions?

Textbook Question

One of the principal components of lemongrass oil is limonene, C₁₀H₁₆. When limonene is treated with excess hydrogen and a platinum catalyst, the product is an alkane of formula C₁₀H₂₀. What can you conclude about the structure of limonene?

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How many different alkenes can be hydrogenated to forma. butane? b. 3-methylpentane?

Key Concepts

Alkenes

Hydrogenation

Structural Isomers

Watch next

How many different alkenes can be hydrogenated to form
a. butane?
b. 3-methylpentane?