See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Determining the Most Acidic Compound **Step 1: Identify the acidic hydrogens** All four compounds are cyclic ethers/thioethers. Acidity arises from $\alpha$-hydrogens (hydrogens adjacent to heteroatoms). **Step 2: Apply the effect of heteroatom electronegativity** The more electronegative the heteroatom, the more it withdraws electron density from adjacent C-H bonds, increasing acidity of those hydrogens. Electronegativity order: $O > S$ **Step 3: Analyze each option** - **(A) Pyran:** One oxygen; $\alpha$-H moderately activated - **(B) Thiopyran:** One sulfur (less electronegative than O); weaker activation - **(C) 1,4-Dioxane:** **Two oxygens** in the ring; $\alpha$-hydrogens flanked by two electronegative oxygen atoms - **(D) 1,4-Dithiane:** Two sulfurs; weaker activation than dioxane **Step 4: Effect of multiple heteroatoms** In option (C), each $\alpha$-hydrogen is adjacent to **two oxygen atoms**. The cumulative electron-withdrawing effect of both oxygens maximally stabilizes the conjugate base (anion), making the $\alpha$-H most acidic. **Answer: (C)** — 1,4-Dioxane is most acidic because its $\alpha$-hydrogens experience the strongest electron-withdrawal from two highly electronegative oxygen atoms.