Question

Acetaldehyde and benzaldehyde can be best distinguished by:

• A. 2,4 DNP test
• B. Tollens' test
• C. Sodium bicarbonate test
• D. Fehling's test

Hint:

The sodium bicarbonate test is a simple way to distinguish between aliphatic and aromatic aldehydes, as aromatic aldehydes like benzaldehyde react with sodium bicarbonate to release CO$_2$.

Answer 1

The Correct Option is C

Acetaldehyde (an aliphatic aldehyde) and benzaldehyde (an aromatic aldehyde) can be distinguished by the sodium bicarbonate test. In this test, aldehydes with an aromatic ring (like benzaldehyde) react with sodium bicarbonate to release carbon dioxide gas, whereas aliphatic aldehydes (like acetaldehyde) do not show this reaction.
Therefore, benzaldehyde gives a positive result with sodium bicarbonate, whereas acetaldehyde does not.
- 2,4 DNP test is used to detect aldehydes and ketones but cannot differentiate between acetaldehyde and benzaldehyde.
- Tollens' test detects aldehydes by forming a silver mirror, but it does not distinguish between acetaldehyde and benzaldehyde.
- Fehling's test is used to distinguish reducing sugars and aldehydes, but it is not the best test for distinguishing between acetaldehyde and benzaldehyde.
Thus, the correct answer is Sodium bicarbonate test.