Separation of Phenol (A) and Aromatic Carboxylic Acid (B) using Sodium Bicarbonate (NaHCO3)

Phenol (A) and aromatic carboxylic acid (B) can be separated easily by using a solution of sodium bicarbonate (NaHCO3). This method is based on the difference in their acid-base properties.

1. Acid-Base Properties of Phenol and Aromatic Carboxylic Acid
- Phenol (A): Phenol is a weak acid and does not readily dissociate in water. It does not react with sodium bicarbonate.
- Aromatic Carboxylic Acid (B): Aromatic carboxylic acids are stronger acids than phenol. They readily dissociate in water to form carboxylate ions, which can react with sodium bicarbonate.

2. Reaction between Aromatic Carboxylic Acid and Sodium Bicarbonate
When an aromatic carboxylic acid (B) is treated with a solution of sodium bicarbonate (NaHCO3), the following reaction occurs:

RCOOH + NaHCO3 → RCOONa + H2O + CO2

The carboxylic acid (B) reacts with sodium bicarbonate to form a carboxylate salt (RCOONa), water (H2O), and carbon dioxide gas (CO2). This reaction is known as an acid-base reaction.

3. Separation Procedure
The separation of phenol (A) and aromatic carboxylic acid (B) using sodium bicarbonate can be carried out as follows:

Step 1: Prepare a solution of sodium bicarbonate by dissolving it in water.
Step 2: Add the mixture of phenol (A) and aromatic carboxylic acid (B) to the sodium bicarbonate solution.
Step 3: Stir the mixture gently.
Step 4: Observe the formation of effervescence (bubbling) due to the evolution of carbon dioxide gas. This effervescence indicates the presence of aromatic carboxylic acid (B).
Step 5: Separate the two layers formed. The top layer will contain phenol (A), and the bottom layer will contain the sodium carboxylate salt (RCOONa) of the aromatic carboxylic acid (B).
Step 6: Acidify the bottom layer by adding dilute hydrochloric acid (HCl) to regenerate the aromatic carboxylic acid (B). The carboxylic acid will separate as an oily layer.
Step 7: Finally, the phenol (A) can be recovered from the top layer by extraction with an organic solvent.

Conclusion
In conclusion, the separation of a mixture containing a lighter phenol (A) and an aromatic carboxylic acid (B) can be achieved by using a solution of sodium bicarbonate. The difference in their acid-base properties allows the aromatic carboxylic acid to react with sodium bicarbonate, forming a carboxylate salt and liberating carbon dioxide gas. This reaction facilitates the separation of the two components.

Carboxylic acids dissolve in NaHCO 3 but phenols do not.