See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

## Analysis of Acid Dissociation Constants **Key Principle:** Lower $K_a$ means weaker acid. Electron-withdrawing groups (EWG) attached to the carboxyl carbon **increase** acid strength by stabilizing the conjugate base anion. **Evaluating each acid:** **(A) $CH_3CHFCOOH$** - Fluorine is directly bonded to the carbon **adjacent to** $COOH$ (β-position) - F is EWG but at β-position → weak inductive effect - Minimal stabilization of $COO^-$ → **weakest acid** **(B) $FCH_2CH_2COOH$** - Fluorine at γ-position (two carbons away from $COOH$) - Very weak inductive effect at this distance - Comparable weakness to (A) **(C) $BrCH_2CH_2COOH$** - Bromine at γ-position like (B), but Br is less electronegative than F - Even weaker EWG effect → weak acid but **slightly stronger** than (B) **(D) $CH_3CHBrCOOH$** - Bromine directly bonded to the α-carbon (α-position) - Direct inductive effect strongly stabilizes $COO^-$ - **Strongest acid** among all four **Order of acid strength:** (D) > (C) ≈ (B) > **(A)** **Answer: (A)** has the lowest $K_a$ because the fluorine is too far from the carboxyl group to effectively stabilize the conjugate base through the inductive effect.