Question

Which one of the following reacts with $HCN$ and Tollens reagent, but is not oxidised by Fehling’s solution?

• A. Methanal
• B. Ethanal
• C. Benzaldehyde
• D. Acetone

Answer 1

Answer: (C)

with $HCN$ all carbonyl compound give reaction.
with Tollen's reagent aldehyde undergoes reaction while ketone does not. and with fehling's solution only aliphaticaldehyde give reaction.
methanal and ethanal:- aliphatic aldehyde hence, give fehling test. acetone:- do not give fehling as well as tollen's test.
Benzaldehyde:− being aldehyde reacts with $HCN$ and Tollen’s reagent and being aromatic it does not react with Fehling solution.