Chemistry Carboxylic Acids MDCAT 2017
PMDC Verified Question 75 of 94
Identify the product X in the following reaction:
\( \text{CH}_3\text{COOH} + \text{PCl}_5 \xrightarrow{\text{Yields}} \text{X} + \text{POCl}_3 + \text{HCl} \)
A
\( \text{CH}_3\text{COCl} \)
B
\( \text{CH}_3\text{COCH}_2\text{Cl}_2 \)
C
\( \text{CH}_3\text{COCl}_2 \)
D
\( \text{CH}_2\text{COCl}_2 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

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

Reacting a carboxylic acid with phosphorus pentachloride (\( \text{PCl}_5 \)) replaces the hydroxyl group with a single chlorine atom, generating an acyl chloride.

Formula:

$$ \text{R-COOH} + \text{PCl}_5 \longrightarrow \text{R-COCl} + \text{POCl}_3 + \text{HCl} $$

Solution:

  • The reactant is acetic acid (\( \text{CH}_3\text{COOH} \)).


  • The substitution yields acetyl chloride, which has the formula \( \text{CH}_3\text{COCl} \).


Why other options are incorrect:

Options B, C, and D depict chemically impossible or structurally flawed hypervalent carbon compounds or incorrect halogen substitutions.

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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