Formation of Salicylic acid from phenol (Kolbe's reaction) is an example of

Options

A. Electrophilic addition reaction
B. Nucleophilic addition reaction
C. Electrophilic substitution reaction
D. Nucleophilic substitution reaction

Answer

To determine the type of reaction that describes the formation of salicylic acid from phenol via Kolbe's reaction, we can analyze the process step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reaction begins with phenol (C6H5OH) and sodium hydroxide (NaOH).

2. **Formation of Phenoxide Ion**: When phenol reacts with NaOH, it forms the phenoxide ion (C6H5O⁻). This occurs because the hydroxide ion (OH⁻) from NaOH deprotonates the hydroxyl group of phenol, resulting in the formation of a negatively charged ion.

- **Hint**: Look for how bases can deprotonate acids to form their conjugate bases.

3. **Electrophilic Attack**: The phenoxide ion, which is resonance-stabilized, can act as a nucleophile. It attacks carbon dioxide (CO2), which acts as an electrophile. This step is crucial as it leads to the formation of a carboxylate ion.

- **Hint**: Identify the roles of nucleophiles and electrophiles in a reaction.

4. **Formation of Salicylic Acid**: The product of the reaction between the phenoxide ion and CO2 is a carboxylate ion (C6H4(OH)(COO⁻)). When this carboxylate ion is treated with an acid (like H2SO4 or H3O⁺), it leads to the protonation of the carboxylate ion, forming salicylic acid (C6H4(OH)(COOH)).

- **Hint**: Consider how acids can protonate negative charges to form neutral compounds.

5. **Conclusion**: The overall process is an electrophilic substitution reaction, where the phenoxide ion undergoes substitution with CO2 to form salicylic acid.

### Final Answer:
The formation of salicylic acid from phenol via Kolbe's reaction is an example of **electrophilic substitution reaction**.