Concept:Thionyl chloride (\( \text{SOCl}_2 \)) is the most efficient reagent for converting a carboxylic acid into an acyl chloride (acid chloride).
Formula:$$ \text{CH}_3\text{COOH} + \text{SOCl}_2 \longrightarrow \text{CH}_3\text{COCl} + \text{SO}_2\uparrow + \text{HCl}\uparrow $$
Solution:- The hydroxyl group (\( -\text{OH} \)) of the acetic acid is nucleophilically substituted by a chlorine atom.
- This forms acetyl chloride (\( \text{CH}_3\text{COCl} \)).
- The byproducts are sulfur dioxide (\( \text{SO}_2 \)) and hydrogen chloride (\( \text{HCl} \)), both of which escape as gases, driving the reaction to completion.
Why other options are incorrect:Options B and D incorrectly suggest the cleavage of the C-C bond to form methyl chloride (\( \text{CH}_3\text{Cl} \)). Option C incorrectly depicts an ester.
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