Chemical test to differentiate between esters and carboxylic acid

Here is a chemical test to differentiate between esters and carboxylic acids:

Test: Reaction with Sodium Carbonate ($\text{Na}_2\text{CO}_3$) or Sodium Bicarbonate ($\text{NaHCO}_3$).

Procedure:

1. Add a small amount of sodium carbonate solution (or solid) to separate samples of the unknown organic compounds.
2. Observe for any gas evolution.

Observations and Explanation:

• Carboxylic Acid: When a carboxylic acid is added to sodium carbonate or sodium bicarbonate, it will react to produce carbon dioxide gas. This will be observed as effervescence (fizzing or bubbling). $$\text{RCOOH} + \text{NaHCO}_3 \longrightarrow \text{RCOONa} + \text{H}_2\text{O} + \text{CO}_2(\text{g})$$ Carboxylic acids are acidic enough to displace carbonic acid from its salts.
• Ester: When an ester is added to sodium carbonate or sodium bicarbonate, there will be no visible reaction (no effervescence). Esters are neutral compounds and are not acidic enough to react with carbonates or bicarbonates.

This test clearly distinguishes between the two functional groups based on the acidity of carboxylic acids.

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