Chemistry

Chemistry

Problem

Four carboxylic acids are listed below. I. 2,2-dichloroethanoic acid (Cl2_2CHCOOH) II. 3,3,3-trifluoropropanoic acid (F3_3CCH2_2COOH) III. 2-methoxyethanoic acid (CH3_3OCH2_2COOH) IV. 4-chlorobutanoic acid (ClCH2_2CH2_2CH2_2COOH) Which sequence correctly ranks their acid strengths from greatest to least? a) II > I > IV > III b) I > II > IV > III c) I > II > III > IV d) I > IV > II > III
Intuitive explanation

Acid strength in carboxylic acids depends on how well the conjugate base (the carboxylate anion) is stabilized after losing a proton. Electron-withdrawing groups nearby pull electron density away from the COO−\text{COO}^-, making it more stable and the acid stronger. The key is to identify which groups are most electronegative and closest to the carboxyl group—proximity and electronegativity both matter. Compare the number and position of electron-withdrawing atoms, and remember that inductive effects weaken with distance along the carbon chain.

Intuitive explanation

Acid strength in carboxylic acids depends on how well the conjugate base (the carboxylate anion) is stabilized after losing a proton. Electron-withdrawing groups nearby pull electron density away from the COO−\text{COO}^-, making it more stable and the acid stronger. The key is to identify which groups are most electronegative and closest to the carboxyl group—proximity and electronegativity both matter. Compare the number and position of electron-withdrawing atoms, and remember that inductive effects weaken with distance along the carbon chain.

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