See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis: Strongest Carbon Acid **Key Concept:** Carboxylic acid strength depends on stabilization of the conjugate base (carboxylate anion). Electron-withdrawing groups and resonance stabilization increase acidity. **Evaluating each option:** **(A) $CH_2(COOC_2H_5)_2$** - Two ester groups (electron-withdrawing by induction) - However, esters are weaker acids than carboxylic acids (~pKa 13-14) **(B) Cyclohexanone-1,4-dione (structure shown)** - Two conjugated carbonyl groups on the ring - Deprotonation gives an anion stabilized by **resonance across both carbonyls** - The negative charge is delocalized: $\text{C}^-=C(-C=O)_2$ resonance forms - pKa ≈ 5-6 (very strong for a carbon acid) **(C) $CH_3COCH_2COOC_2H_5$** - Single carboxylic acid with one ketone nearby - Less resonance stabilization than option B - pKa ≈ 9-10 **(D) Bicyclic diketone** - Two carbonyl groups but less optimal conjugation geometry - Weaker stabilization than the symmetrical 1,4-dione system **Answer: (B)** The 1,4-diketone allows the **conjugate base anion to be stabilized by extensive resonance delocalization across both carbonyl π-systems**, making it the strongest carbon acid among the choices.