Chemistry Hydrocarbons DUHS 2024
PMDC Verified Question 5 of 65
In Friedel Craft acylation, an acyl group is introduced in benzene ring in the presence of catalyst:
A
\( \text{AlCl}_3 \)
B
\( \text{H}_2\text{SO}_4 \)
C
Sunlight
D
\( \text{V}_2\text{O}_5 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( \text{AlCl}_3 \)
Concept:

Friedel-Crafts acylation requires the generation of a powerful acylium electrophile from an acyl halide. This requires a Lewis acid.

Solution:

  • Acyl chlorides (e.g., \( \text{RCOCl} \)) are not electrophilic enough to attack benzene on their own.


  • A Lewis acid like anhydrous \( \text{AlCl}_3 \) is used as a catalyst. It accepts a lone pair from the chlorine atom, breaking the C-Cl bond.


  • This creates the highly reactive acylium ion (\( \text{R}-\text{C}^+=\text{O} \)), which then successfully substitutes onto the aromatic ring.


Why other options are incorrect:

  • \( \text{H}_2\text{SO}_4 \) is a Brønsted acid used in nitration and sulfonation.


  • Sunlight initiates free radical substitution, not electrophilic aromatic substitution.


  • \( \text{V}_2\text{O}_5 \) is a catalyst for the severe oxidation/cleavage of benzene.

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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