Question

Which of the following will have the highest acidic strength?

(a) Butanoic acid

(b) 2-Chlorobutanoic acid

(c) 3-Chlorobutanoic acid

(d) 4-Chlorobutanoic acid

This question was addressed to me in an interview for job.

My query is from Carboxylic Acids Chemical Reactions topic in division Aldehydes, Ketones and Carboxylic Acids of Chemistry – Class 12

Answer 1

Right choice is (b) 2-Chlorobutanoic acid

To explain I would say: Halogen substituted carboxylic acids are stronger acid than their respective parent acids, because of the electron withdrawing and stabilizing nature of the halogen. Furthermore, as the distance of the halogen form the COOH group increases, the electron withdrawing influence decreases, and therefore the acidic character decreases.