Concept:To convert a carboxylic acid into an acyl chloride (acid chloride), specialized inorganic chlorinating agents are required to substitute the \( -\text{OH} \) group with a \( -\text{Cl} \).
Formula:$$ \text{CH}_3\text{COOH} + \text{PCl}_5 \longrightarrow \text{CH}_3\text{COCl} + \text{POCl}_3 + \text{HCl} $$
Solution:- Phosphorus pentachloride (\( \text{PCl}_5 \)) acts effectively, ripping the oxygen atom away and replacing it with chlorine.
- Other standard reagents for this include \( \text{PCl}_3 \) and \( \text{SOCl}_2 \).
Why other options are incorrect:\( \text{HCl} \) does not react this way because \( \text{OH}^- \) is a terrible leaving group in acid. \( \text{POCl}_3 \) is actually a byproduct of the \( \text{PCl}_5 \) reaction, not the primary reactant.
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.