Concept:Thionyl chloride (\( \text{SOCl}_2 \)) reacts with carboxylic acids in a 1:1 molar ratio, creating an acyl chloride, sulfur dioxide gas, and hydrogen chloride gas.
Solution:- We must identify the correct acid: Ethanoyl chloride implies the starting material must be ethanoic acid (acetic acid, \( \text{CH}_3\text{COOH} \)).
- Check the balancing: 1 mole of \( \text{CH}_3\text{COOH} \) + 1 mole of \( \text{SOCl}_2 \) correctly balances to yield 1 mole of \( \text{CH}_3\text{COCl} \) + 1 mole of \( \text{SO}_2 \) + 1 mole of \( \text{HCl} \).
Why other options are incorrect:Option A and D use propanoic acid (\( \text{CH}_3\text{CH}_2\text{COOH} \)) and incorrectly list the reagent as "SOCl". Option C utilizes methanoic (formic) acid, which yields formyl chloride.
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