Question

Given below are the four isomeric compounds \(P, Q, R, S\):
\(P\): Aromatic compound containing an \(-\mathrm{OH}\) group 
\(Q\): Aromatic compound containing an \(-\mathrm{CHO}\) group (aldehyde) 
\(R\): Aromatic compound containing a ketone group 
\(S\): Aromatic compound containing a ketone group Identify the correct statements from below: 
[A.] \(Q, R\) and \(S\) will give precipitate with \(2,4\)-DNP. 
[B.] \(P\) and \(Q\) will give positive Baeyer’s test. 
[C.] \(Q\) and \(R\) will give sooty flame. 
[D.] \(R\) and \(S\) will give yellow precipitate with \(I_2/\mathrm{NaOH}\). 
[E.] \(Q\) alone will deposit silver with Tollens’ reagent. Choose the correct option.

• A. A, B, D and E only
• B. C and E only
• C. A and E only
• D. A, C and E only

Hint:

Remember: Tollens’ test is specific for aldehydes, while \(2,4\)-DNP reacts with all aldehydes and ketones.

Answer 1

The Correct Option is D

Step 1: Test with \(2,4\)-DNP \(2,4\)-DNP gives a precipitate with aldehydes and ketones.
\(Q\): Aldehyde \(\checkmark\)
\(R\): Ketone \(\checkmark\)
\(S\): Ketone \(\checkmark\)
\(P\): Alcohol \(\times\) \[ \Rightarrow \text{Statement A is true.} \]
Step 2: Baeyer’s test Baeyer’s test is given by compounds containing \(\mathrm{C=C}\) or \(\mathrm{C\equiv C}\).
\(P\): Phenolic compound, no alkene \(\times\)
\(Q\): Aldehyde, no alkene \(\times\) \[ \Rightarrow \text{Statement B is false.} \]
Step 3: Sooty flame test Aromatic compounds generally burn with a sooty flame due to high carbon content. \[ Q \text{ and } R \text{ are aromatic } \Rightarrow \text{ sooty flame} \] \[ \Rightarrow \text{Statement C is true.} \]
Step 4: Iodoform test Iodoform test is given by:
Methyl ketones (\(-\mathrm{COCH_3}\))
Ethanol Only compound \(S\) is a methyl ketone, not \(R\). \[ \Rightarrow \text{Statement D is false.} \]
Step 5: Tollens’ test Tollens’ reagent gives a silver mirror with aldehydes. \[ Q \text{ is an aldehyde } \Rightarrow \text{ positive} \] Others are ketones or alcohols. \[ \Rightarrow \text{Statement E is true.} \] Final Conclusion: \[ \boxed{\text{A, C and E only}} \]