Chemistry – Organic chemistry - Formulae, functional groups and terminology | e-Consult

Three chemical tests to distinguish between a carboxylic acid and an alcohol are:

1. Reaction with Sodium Bicarbonate (NaHCO₃): A carboxylic acid reacts with sodium bicarbonate to produce carbon dioxide gas.

   Chemical Principle: Carboxylic acids contain the -COOH group. The hydrogen atom of the -COOH group is acidic and can donate a proton (H⁺) to the bicarbonate ion (HCO₃^-). This forms carbonic acid (H₂CO₃), which is unstable and decomposes into carbon dioxide (CO₂), water (H₂O), and bicarbonate (HCO₃^-). The evolution of CO₂ is a positive test for a carboxylic acid.

2. Reaction with Sodium Metal (Na): Carboxylic acids react with sodium metal to produce hydrogen gas.

   Chemical Principle: Carboxylic acids contain a hydrogen atom bonded to an oxygen atom in the -COOH group. This hydrogen atom can be abstracted by sodium, forming hydrogen gas (H₂) and a carboxylate ion. This reaction is a positive test for a carboxylic acid.

3. Reaction with an ester in the presence of a catalyst (e.g., dilute acid): A carboxylic acid can be esterified with an alcohol in the presence of an acid catalyst. This reaction is readily reversible.

   Chemical Principle: The reaction is an equilibrium process. The presence of an ester (a product of the reaction) shifts the equilibrium towards the reactants (carboxylic acid and alcohol), indicating the presence of a carboxylic acid. This is a positive test for a carboxylic acid.