See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Step-by-Step Solution **Starting Material Analysis:** The substrate is 4-methylbenzenesulfonic acid ($p$-toluenesulfonic acid): $SO_3H$ and $Me$ groups in para positions. **Reaction Conditions:** $CH_3COONa$ (excess) in aqueous solution provides a basic medium with acetate ions, which are weak bases and good nucleophiles. **Key Chemical Principles:** 1. **Sulfonic acid vs. carboxylic acid acidity:** $SO_3H$ is ~1000× more acidic than $CH_3COOH$ (stronger acid than acetic acid) 2. **In basic aqueous solution:** The stronger acid ($SO_3H$) is deprotonated first to form $SO_3^-$ (sulfonate ion), which is stable and not displaced. The weaker acid ($CH_3COOH$) remains largely un-ionized. 3. **No nucleophilic substitution on aromatic ring:** Acetate ions cannot displace either group via $S_N Ar$ because aromatic rings are too unreactive under these mild conditions. 4. **Acid-base equilibrium dominates:** Only proton transfer occurs: $$\text{ArSO}_3H + CH_3COO^- \rightleftharpoons \text{ArSO}_3^- + CH_3COOH$$ **Product Formation:** Sodium sulfonate salt precipitates out, leaving acetic acid in solution. **Why other options are wrong:** - **(A):** Benzene ring cannot form—no reduction conditions - **(B):** Esterification requires acidic catalyst, not achieved here - **(D):** $SO_3H$ group is too stable to be replaced; would need completely different mechanism **Answer: (C)** — Sodium salt of sulfonic acid + acetic acid