Cautiously add a few drops or a few crystals of the unknown compound to 1 mL of water and touch the test tube to see if heat is evolved. If the test tube is warm, then the test is positive for an acid anhydride or an acyl halide, since water will react with these compounds to form the carboxylic acid with the evolution of heat. Add 1 mL of methanol to dissolve the sample. The solution is slowly poured into 1 mL of a saturated solution of sodium bicarbonate. Evolution of carbon dioxide gas is a positive test for the presence of the product carboxylic acid.
Production of heat and carbon dioxide gas is a positive test.
Higher aliphatic anhydrides and aromatic anhydrides are not readily hydrolyzed with water and thus may not give a positive test.
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