Chemistry Aldehydes & Ketones NUMS 2024
PMDC Verified Question 11 of 94
Identify the correct increasing order of reactivity of carbonyl compound towards nucleophilic addition: (Wrong)
A
\( HCHO < CH_3CHO < CH_3COCH_3 < CH_3CH_2CHO \)
B
\( CH_3CHO < CH_3COCH_3 < CH_3CH_2CHO < HCHO \)
C
\( CH_3CH_2CHO < CH_3COCH_3 < HCHO < CH_3CHO \)
D
\( CH_3CH_2CHO < CH_3COCH_3 < CH_3CHO < HCHO \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \( CH_3CH_2CHO < CH_3COCH_3 < CH_3CHO < HCHO \)
Concept:

Reactivity towards nucleophiles relies on electrophilicity and steric hindrance. Note: This question contains flawed options structurally, but we align with the provided answer key.

Solution:

  • Fundamentally, aldehydes are vastly more reactive than ketones. Formaldehyde is the most reactive of all.


  • The true reactivity order is: Ketones < Large Aldehydes < Small Aldehydes < Formaldehyde.


  • Specifically, Acetone (\( CH_3COCH_3 \)) should be the least reactive due to two bulky methyl groups.


  • The provided answer key selects Option D. However, Option D incorrectly places Propanal (\( CH_3CH_2CHO \)) as less reactive than Acetone. The textbook notes explicitly state this question is flawed ("There is no correct answer..."), but for exam mapping purposes, Option D is recorded.


Why other options are incorrect:

All options fail to perfectly map the established chemical truth (Acetone < Propanal < Acetaldehyde < Formaldehyde), but Option D is strictly selected by the institutional key.

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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