CBSE Class 12 · 2023 · Aldehydes Ketones and Carboxylic AcidsMultiple Choice

Which one of the following has the lowest pKₐ value?

(A)CH₃–COOH
(B)O₂N–CH₂–COOH✓ Correct
(C)Cl–CH₂–COOH
(D)HCOOH

Answer: (B)

Solution

Lowest pK

_{a}

= strongest acid. –NO

_{2}

has the strongest −I pull of the substituents listed, stabilising the carboxylate most:
O

_{2}

NCH

_{2}

COOH > ClCH

_{2}

COOH > HCOOH > CH

_{3}

COOH in acidity.
Correct option: (B).

CBSE Class 12 Board · 2023 · Single correct option

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