Question

The compound which does not react with ammonical silver nitrate solution is:

• A. 2-methyl propanal
• B. 2-methyl cyclopentanone
• C. 3-methyl benzaldehyde
• D. Methanoic acid

Hint:

For Tollens’ test:

- Positive for aldehydes and formic acid.

- Ketones are generally non-reactive.

- Identify the functional group to predict reactivity.

Answer 1

The Correct Option is B

Ammonical silver nitrate, known as Tollens’ reagent (\({[Ag(NH3)2]^+}\)), is used to detect aldehydes and certain reducing compounds, which reduce \({Ag^+}\) to metallic silver, forming a silver mirror.
Step 1: Tollens’ reagent reactivity
- Aldehydes: Oxidized to carboxylic acids, reducing \({Ag^+}\).
- Ketones: Typically non-reactive due to lack of an oxidizable hydrogen.
- Methanoic acid: Reduces Tollens’ reagent due to its aldehyde-like reducing property.
Step 2: Analyze options
- (A) 2-methyl propanal (\({(CH3)2CHCHO\))}: An aldehyde, reacts to form a silver mirror.
- (B) 2-methyl cyclopentanone: A ketone, does not react with Tollens’ reagent.
- (C) 3-methyl benzaldehyde (\({CH3-C6H4-CHO}\)): An aromatic aldehyde, reacts with Tollens’ reagent.
- (D) Methanoic acid (\({HCOOH}\)): Reduces Tollens’ reagent due to its reducing nature.
Step 3: Conclusion
Only 2-methyl cyclopentanone, a ketone, does not react, matching option (B).