See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: The acidity of carboxylic acids is enhanced by electron-withdrawing groups (EWGs) through the inductive effect. Stronger EWGs or EWGs closer to the carboxyl group increase acidity more effectively. Analysis of each option to find where the second acid is stronger than the first: (a) CH3CO2H (acetic acid) vs CH2FCO2H (fluoroacetic acid): - CH3 is an electron-donating group, while F is a strongly electron-withdrawing halogen. - Fluorine has the highest electronegativity among halogens and exerts a strong -I (inductive withdrawal) effect. - CH2FCO2H is significantly more acidic than CH3CO2H. - pKa of acetic acid ≈ 4.75; pKa of fluoroacetic acid ≈ 2.59. - Therefore, the second acid (CH2FCO2H) IS stronger than the first (CH3CO2H). ✓ (b) CH2FCO2H vs CH2ClCO2H: - Both have a halogen alpha to the carboxyl group. - F is more electronegative than Cl, so the inductive withdrawal effect of F is greater than Cl. - pKa of fluoroacetic acid ≈ 2.59; pKa of chloroacetic acid ≈ 2.86. - CH2FCO2H is MORE acidic than CH2ClCO2H. - Therefore, the second acid (CH2ClCO2H) is WEAKER than the first. ✗ (c) CH2ClCO2H vs CH2BrCO2H: - Cl is more electronegative than Br, so CH2ClCO2H has a stronger inductive effect than CH2BrCO2H. - pKa of chloroacetic acid ≈ 2.86; pKa of bromoacetic acid ≈ 2.90. - CH2ClCO2H is MORE acidic than CH2BrCO2H. - Therefore, the second acid is WEAKER than the first. ✗ (d) CH3CH2CHFCO2H vs CH3CHFCH2CO2H: - In the first acid, F is on the alpha carbon (directly adjacent to COOH). - In the second acid, F is on the beta carbon (one carbon farther from COOH). - Inductive effect diminishes with distance; alpha substitution provides stronger acid-strengthening effect than beta substitution. - Therefore, the first acid (F on alpha carbon) is MORE acidic than the second (F on beta carbon). ✗ Only option (a) has the second acid stronger than the first. Therefore, the correct answer is A.