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

Carbene

Organic Chemistry

10. Addition Reactions

Carbene

Previous problemNext problem

8:21 minutes

Problem 79f

Textbook Question

In addition to radicals, anions, and cations, a fourth class of reactive intermediates is carbenes. A neutral species, the simplest carbene has a molecular formula of CH₂.
(f) Cyclopropanation of (E)- and (Z)-3-methylhex-3-ene gives two different products. Rationalize this outcome.

Verified step by step guidance

Step 1: Understand the concept of carbenes. Carbenes are neutral reactive intermediates with a divalent carbon atom that has two nonbonded electrons. The simplest carbene is methylene (CH₂), which can react with alkenes to form cyclopropane rings through a process called cyclopropanation.

Step 2: Analyze the structures of (E)- and (Z)-3-methylhex-3-ene. The (E)-isomer has the substituents on opposite sides of the double bond, while the (Z)-isomer has the substituents on the same side. This stereochemistry affects the spatial arrangement of the substituents during the reaction.

Step 3: Examine the reaction mechanism. The carbene (CH₂) reacts with the double bond of the alkene to form a cyclopropane ring. The stereochemistry of the starting alkene determines the stereochemistry of the cyclopropane products.

Step 4: Rationalize the formation of two different products for each isomer. For the (E)-isomer, the substituents on opposite sides of the double bond lead to two distinct stereoisomers of the cyclopropane product due to the approach of the carbene from either side of the double bond. Similarly, for the (Z)-isomer, the substituents on the same side of the double bond result in two stereoisomers of the cyclopropane product.

Step 5: Conclude that the stereochemistry of the starting alkene dictates the stereochemistry of the cyclopropane products. The reaction preserves the relative spatial arrangement of the substituents, leading to stereoisomeric products for both (E)- and (Z)-3-methylhex-3-ene.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Carbenes

Carbenes are neutral reactive intermediates characterized by a carbon atom with only six valence electrons, making them highly reactive. The simplest carbene, methylene (CH₂), can participate in various reactions, including cyclopropanation, where it adds across double bonds to form three-membered rings. Understanding carbenes is crucial for predicting the outcomes of reactions involving alkenes.

Cyclopropanation

Cyclopropanation is a chemical reaction that involves the addition of a carbene to an alkene, resulting in the formation of a cyclopropane ring. This reaction can lead to different stereochemical outcomes depending on the geometry of the starting alkene (E or Z isomers). The stereochemistry of the alkene influences the orientation of the carbene attack, which is essential for rationalizing the formation of distinct products.

Stereochemistry

Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the context of (E)- and (Z)-3-methylhex-3-ene, the different spatial arrangements lead to different reactivity patterns when reacting with carbenes. Recognizing the stereochemical differences is vital for understanding why cyclopropanation yields different products from these isomers.

Watch next

Master General properties of cyclopropanation. with a bite sized video explanation from Johnny

Start learning