Question

Electrophile used in Kolbe’s reaction is:

• A. Carbondioxide
• B. Dichlorocarbene
• C. Carbommonoxide
• D. Acyl carbocation

Hint:

For Kolbe’s reactions:

- Kolbe electrolysis: Forms alkanes via decarboxylation of carboxylate salts.

- Kolbe-Schmitt: Phenol reacts with \({CO_2}\) to form salicylic acid.

- Identify the electrophile based on the reaction context.

Answer 1

The Correct Option is A

The Kolbe-Schmitt reaction involves the reaction of a phenoxide ion with carbon dioxide to form salicylic acid, a key step often confused with Kolbe’s electrolysis in some curricula. In this context, we identify the electrophile used.
Step 1: Understand Kolbe’s reaction
Kolbe’s electrolysis produces alkanes from carboxylate salts, but the Kolbe-Schmitt reaction is relevant here, where sodium phenoxide reacts with \({CO_2}\) under heat and pressure to form salicylic acid. The electrophilic carbon in \({CO_2}\) is attacked by the nucleophilic phenoxide ion.
Step 2: Identify the electrophile
- (A) Carbondioxide: \({CO_2}\) has an electron-deficient carbon, acting as an electrophile in the Kolbe-Schmitt reaction, correct.
- (B) Dichlorocarbene: Used in Reimer-Tiemann reaction, not Kolbe’s.
- (C) Carbommonoxide: Not involved in Kolbe’s reactions.
- (D) Acyl carbocation: Relevant to Friedel-Crafts acylation, not Kolbe’s.
Step 3: Conclusion
The electrophile in the Kolbe-Schmitt reaction is carbon dioxide, matching option (A).