Question

Give a simple chemical test to distinguish between ethanoic acid and ethanal.

Hint:

- The iodoform test specifically identifies compounds with a methyl group directly attached to a carbonyl group, like ethanal or methyl ketones. - Ethanoic acid does not have a methyl group on its carbonyl group, so it does not give a yellow precipitate in the test.

Answer 1

A simple test to distinguish between ethanoic acid and ethanal is the iodoform test. When ethanal (acetaldehyde) is heated with NaOH and iodine (I\(_2\)), it forms a yellow precipitate of iodoform (CHI\(_3\)). This occurs because ethanal contains the structure –CHO (an aldehyde group) that can undergo oxidation and give a yellow iodoform precipitate. However, ethanoic acid (acetic acid), which contains a carboxyl group (–COOH), does not react in the same way. Therefore, ethanoic acid will not produce a yellow precipitate with NaOH and iodine, making this test a reliable way to differentiate the two.