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

Verified step by step guidance

1. 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.
2. 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.
3. 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).
4. 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.
5. 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.

Key Concepts

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.