Question
Explain laboratory tests for carboxyl (- COOH) group.
✓
Answer
The presence of $- COOH$ group in carboxylic acids is identified by the following tests :
(1) Litmus test : (valid for water soluble substances)
Aqueous solution of Organic compound containing $- COOH$ group turns blue litmus red which indicates the presence of acidic functional group.
(2) Sodium bicarbonate test: When sodium bicarbonate is added to an organic compound containing $- COOH$ group, a brisk effervescence of carbon dioxide gas is evolved. Water insoluble acid goes in solution and gives precipitate an acidification with cone. $HCl$. This indicates the presence of - $COOH$ group.
(3) Ester test: One drop of concentrated sulfuric acid is added to a mixture of given organic compound containing $- COOH$ group and one $mL$ of ethanol, the reaction mixture is heated for 5 minutes in hot water bath. After this, hot solution is poured in a beaker containing water, fruity smell of ester confirms the presence of carboxylic acid.
(1) Litmus test : (valid for water soluble substances)
Aqueous solution of Organic compound containing $- COOH$ group turns blue litmus red which indicates the presence of acidic functional group.
(2) Sodium bicarbonate test: When sodium bicarbonate is added to an organic compound containing $- COOH$ group, a brisk effervescence of carbon dioxide gas is evolved. Water insoluble acid goes in solution and gives precipitate an acidification with cone. $HCl$. This indicates the presence of - $COOH$ group.
(3) Ester test: One drop of concentrated sulfuric acid is added to a mixture of given organic compound containing $- COOH$ group and one $mL$ of ethanol, the reaction mixture is heated for 5 minutes in hot water bath. After this, hot solution is poured in a beaker containing water, fruity smell of ester confirms the presence of carboxylic acid.
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