Phenol can be converted into salicyclic acid by heating with :

Options

A. `CO_(2)` and alkali under pressure
B. `C Cl_(4)` and alkali at 340 K
C. `CHCl_(3)` and alkali at 340 K followed by oxidation
D. none of the above

Answer

To convert phenol into salicylic acid, we can follow these steps:

### Step 1: Identify the Reactants
We start with phenol, which has the chemical structure of a hydroxyl group (-OH) attached to a benzene ring.

**Hint:** Recognize that phenol is a simple aromatic compound with a hydroxyl group.

### Step 2: Choose the Correct Reaction Conditions
The conversion of phenol to salicylic acid requires specific conditions. The correct conditions involve heating phenol with carbon dioxide (CO2) and an alkali (such as sodium hydroxide) under high pressure.

**Hint:** Look for conditions that facilitate the introduction of a carboxyl group (-COOH) into the aromatic ring.

### Step 3: Understand the Reaction Mechanism
When phenol is treated with CO2 and alkali at a pressure of 427 atm and a temperature of 400 K, a sodium salt of salicylic acid is formed. This process is known as the Kolbe’s electrolysis or Kolbe's reaction.

**Hint:** Remember that the reaction involves the substitution of a hydrogen atom on the benzene ring with a carboxylate group (-COONa).

### Step 4: Acidification of the Sodium Salt
The sodium salt of salicylic acid (formed in the previous step) can be converted to salicylic acid by acidification. When the sodium salt is treated with an acid (like HCl), the sodium ion (Na+) is replaced by a proton (H+), resulting in the formation of salicylic acid (C6H4(OH)(COOH)).

**Hint:** Acidification is a common step in organic chemistry to convert salts back to their corresponding acids.

### Step 5: Conclusion
Thus, the overall process of converting phenol to salicylic acid involves heating phenol with CO2 and alkali under pressure, followed by acidification to obtain the final product.

**Final Answer:** Phenol can be converted into salicylic acid by heating with CO2 and alkali under pressure.

### Summary of Steps:
1. Identify phenol as the starting material.
2. Use CO2 and alkali under high pressure and temperature.
3. Understand the mechanism of sodium salt formation.
4. Acidify the sodium salt to obtain salicylic acid.
5. Conclude with the correct reaction conditions.