See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Enolate Formation from Butanone **Objective:** Identify which base most effectively deprotonates the $\alpha$-hydrogen of butanone to form its enolate. ## Step 1: Identify the acidic hydrogen Butanone ($CH_3CH_2-C(=O)-CH_3$) has $\alpha$-hydrogens adjacent to the carbonyl group. The $pK_a$ of these hydrogens is ~19-20 due to carbonyl stabilization of the resulting carbanion. ## Step 2: Apply base strength criterion For maximum enolate formation, we need a base strong enough to deprotonate the $\alpha$-hydrogen completely. The conjugate acid ($BH$) of the base must have $pK_a > 20$. ## Step 3: Evaluate each option | Option | Base | Conjugate Acid | $pK_a$ | Effective? | |--------|------|----------------|--------|-----------| | **(A)** | $C_2H_5ONa$ (ethoxide) | $C_2H_5OH$ | ~15-16 | Weak | | **(B)** | $CH_3COONa$ (acetate) | $CH_3COOH$ | ~4.8 | Too weak | | **(D)** | $NaOH$ | $H_2O$ | ~15.7 | Marginal | | **(C)** | $(C_6H_5)_3CNa$ (triphenylmethide) | $(C_6H_5)_3CH$ | ~31-33 | **Excellent** ✓ | ## Step 4: Why option C is best The triphenylmethide base is an **extremely strong base** with conjugate acid $pK_a \approx 31-33$ (much higher than 20). The three phenyl groups stabilize the positive charge on the conjugate acid through resonance, making it an ideal "super base" for complete enolate formation. **Answer: (C) $(C_6H_5)_3CNa$**