Question

The correct order of decreasing rate of esterification with ethanol is?

• A. (I) Cl-CH2-COOH
• B. (II) CH3-CH2-COOH
• C. (III) CH3-CH-COOH
• D. (IV) (CH3)3C-COOH

Answer 1

(1) I > II > III > IV

Answer 2

The rate of esterification is influenced by inductive effects and steric hindrance. Electron-withdrawing groups like chlorine in (I) increase the electrophilicity of the carbonyl carbon, accelerating the reaction. Alkyl groups are electron-donating, decreasing the rate. Steric hindrance around the carboxyl group also reduces the rate. Thus, (I) is fastest, followed by (II) (propanoic acid), then (III) (isobutyric acid) due to increased steric hindrance, and finally (IV) (pivalic acid) with the most steric hindrance.