Question

In the reaction

the electrophile involved is

• A. dichloromethyl cation \(C^\oplus HCL_2\)
• B. dichloromethyl anion \(C^\ominus HCL_2\)
• C. formyl cation \(C^\oplus HO\)
• D. dichlorocarbene (:CCl₂)

Answer 1

The Correct Option is D

To solve the question about the electrophile involved in the reaction, let's consider the given reaction and options:

The reaction given is the classic Reimer-Tiemann reaction, where chloroform (\(CHCl_3\)) reacts with a phenol in the presence of a strong base like NaOH to form an aldehyde.

During this reaction, the critical step involves the formation of an electrophile from the reagent. The base abstracts a proton from chloroform, leading to the formation of dichlorocarbene \((:CCl_2)\).

Let's evaluate the options:

• Dichloromethyl cation \((C^\oplus HCl_2)\): This is not involved in this reaction.
• Dichloromethyl anion \((C^\ominus HCl_2)\): This anion is not a stable species in this context.
• Formyl cation \((C^\oplus HO)\): This cation is not related to this reaction mechanism.
• Dichlorocarbene \((:CCl_2)\): This is the correct electrophile formed in the reaction by the deprotonation of chloroform by the base, making it highly reactive and suitable for electrophilic attack on the phenol.

Therefore, the correct answer is dichlorocarbene \((:CCl_2)\).

This electrophile then reacts with the phenol to form a new carbon-carbon bond at the ortho position relative to the hydroxyl group, resulting in the formation of an aldehyde after further steps in the reaction.