The carboxylic group can be tested by:

Litmus Test

Put a drop of an aqueous solution of the compound on blue litmus paper. If the blue litmus turns red, acidic nature is indicated.

Sodium Hydrogen Carbonate Test

Add a saturated solution of sodium hydrogen carbonate to an aqueous solution of the compound. If brisk effervescence appear due to evolution of CO2 gas, the carboxylic group is confirmed.

CH3COOH + NaHCO3 → CH3COONa + CO2 ↑ + H2O

Esterification Test

The given organic compound is mixed with absolute ethanol in equal amounts and a few drops of concentrated sulphuric acid are added. The mixture is warmed on a water bath. If a fruity smell (pleasant sweet smell) is obtained, the presence of carboxylic group is confirmed.