The acid shown has $p K_{a} = 4.06$ . Which of the structures A to D is expected to have the lowest $p K_{a}$ ?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: A

The drawn compound is 3-chlorobutanoic acid. The inductive effect of chlorine falls off with distance: 2-chlorobutanoic acid pKa 2.84, 3-chloro 4.06, 4-chloro 4.52. Alkyl-substituted acids (butanoic, 3-methylbutanoic) are weaker still. So 2-chlorobutanoic acid is the strongest.

Practice Aldehydes, Ketones and Carboxylic Acids More on Acidity order and derivative reactivity among drawn carboxylic acids

Previous questionNext question

More questions on Acidity order and derivative reactivity among drawn carboxylic acids

The acid shown has pK_a = 4.76. Which of the structures A to D is the strongest acid? NEET level
The compound shown is compared with an anhydride, an ester and an amide of the same acyl group. Which order of reactivity toward nucleophili... JEE Main level
The acid shown has pK_a = 4.47, while benzoic acid has pK_a = 4.20. The best explanation is JEE Main level
The acid shown has pK_a = 2.17 whereas its para isomer has pK_a = 3.44. The main reason for the greater acidity of the drawn acid is JEE Main level
Which hydrogen of the molecule shown is the most acidic? NEET level
The acid shown is heated with excess ethanol and a few drops of conc. H2SO4 (Fischer esterification). Which structure is the major organic p... JEE Main level

The acid shown has pKa​=4.06. Which of the structures A to D is expected to have the lowest pKa​?

Answer: A

More questions on Acidity order and derivative reactivity among drawn carboxylic acids

The acid shown has $p K_{a} = 4.06$ . Which of the structures A to D is expected to have the lowest $p K_{a}$ ?