Chemistry Aldehydes & Ketones MDCAT 2017
PMDC Verified Question 71 of 94
Both aldehyde and ketones give ____:
A
Tollen's Test
B
Benedict's solution test
C
2,4-DNPH test
D
Sodium nitroprusside test
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: 2,4-DNPH test
Concept:

Identifying a reagent that reacts generically with the carbonyl group vs. one that relies on oxidation properties.

Solution:

  • The 2,4-Dinitrophenylhydrazine (2,4-DNPH) reagent, also known as Brady's reagent, reacts via nucleophilic addition-elimination with the carbonyl group itself.


  • Because both aldehydes and ketones possess an active carbonyl group, they both form yellow, orange, or red hydrazone precipitates with this reagent.


Why other options are incorrect:

Tollen's and Benedict's tests are mild oxidation tests; only aldehydes give positive results because ketones are highly resistant to oxidation. The Sodium nitroprusside test gives a wine-red color with ketones but not aldehydes.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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