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

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4:19 minutes

Problem 27a

Textbook Question

Predict the carbenoid addition products of the following reactions.
(a) cyclohexene + CHCl₃, 50% NaOH/H₂O

Verified step by step guidance

Identify the reaction type: This is a carbenoid addition reaction, where a carbene or carbenoid intermediate is generated and reacts with the alkene to form a cyclopropane ring.

Understand the reagents: CHCl₃ (chloroform) in the presence of a strong base like NaOH generates a dichlorocarbene (:CCl₂) intermediate. This occurs via deprotonation of CHCl₃ by NaOH, followed by elimination of a chloride ion.

Generate the dichlorocarbene intermediate: The reaction mechanism involves the following steps: (1) NaOH deprotonates CHCl₃ to form the trichloromethyl anion (CCl₃⁻), and (2) CCl₃⁻ eliminates a chloride ion (Cl⁻) to form the neutral dichlorocarbene (:CCl₂).

React the dichlorocarbene with cyclohexene: The alkene (cyclohexene) reacts with the dichlorocarbene (:CCl₂) in a concerted mechanism to form a cyclopropane ring. The two π-electrons of the alkene bond with the carbene carbon, resulting in a three-membered ring structure.

Draw the product: The final product is a cyclopropane ring fused to the cyclohexane ring, with two chlorine atoms attached to the cyclopropane carbon. The product can be represented as 7,7-dichlorobicyclo[4.1.0]heptane.

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Key Concepts

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

Carbenoids

Carbenoids are reactive intermediates that resemble carbenes but are stabilized by adjacent groups. They can participate in various reactions, including additions to alkenes. In the context of the given reaction, the carbenoid generated from CHCl3 in the presence of a strong base like NaOH can add to the double bond of cyclohexene, leading to the formation of a halogenated product.

Electrophilic Addition Reactions

Electrophilic addition reactions involve the addition of an electrophile to a nucleophilic site, typically a double bond in alkenes. In this case, the carbenoid acts as an electrophile that adds to the cyclohexene, resulting in the formation of a more stable product. Understanding the mechanism of electrophilic addition is crucial for predicting the outcome of the reaction.

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple possibilities exist. In the reaction of cyclohexene with the carbenoid, the regioselectivity will determine which carbon atom of the double bond the electrophile adds to, influencing the final product's structure. Analyzing the stability of potential products helps predict the major outcome.

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Related Practice

Textbook Question

Show how you would accomplish each of the following synthetic conversions.

(b)

Textbook Question

Predict the carbenoid addition products of the following reactions.

(b)

Textbook Question

Predict the carbenoid addition products of the following reactions.

a. trans-hex-3-ene + CH₂I₂, Zn(Cu)

b. cis-hex-3-ene + CH₂I₂, Zn(Cu)

Textbook Question

Predict the carbenoid addition products of the following reactions.

(c)

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 .

(e) Carbenes have great synthetic utility, especially in the synthesis of cyclopropanes from alkenes. Based on your answers to (a)–(d), show a mechanism for the cyclopropanation of cyclohexene.

Textbook Question

Provide an arrow-pushing mechanism for the cyclopropanation of cyclohexene with methylene carbene. Rationalize the outcome.

Textbook Question

Cyclopropanation using any of the reagents discussed here is stereospecific.

(a) What does this say about the mechanism?

Textbook Question

Predict the product of the following reactions.

(b)

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