Which of the following acids has the smallest dissociation constant?

Options

A. `CH_(3)CHFCOOH`
B. `FCH_(2)CH_(2)COOH`
C. `BrCH_(2)CH_(2)COOH`
D. `CH_(3)CHBrCOOH`

Answer

C

Explanation

Charge dispersal stabilizes and charge intensification destabilizes.
(i) the inductive effect decreases with increases in distance of halogen atom from the caboxylate ion and hence the strength of acid proportionally decreases due to decreases in stability of carboxylate ion.
(II) The acidity increases with the increases in electronegativity of the halogen present due to `-I` effect of stronger electronegativity group. Smallest dissociation constant means weakest acid, which is `BrCH_(2)CH_(2)COOH` because here `Br` (less electromangetic than `F`) is two carbon atoms away from `-COOH`.