Question

Which one of the given compounds is a stronger acid and why?
CH$_2$FCH$_2$COOH or CH$_3$CHFCH$_2$COOH

Hint:

Fluorine is a highly electronegative element. The closer it is to the carboxyl group, the stronger the acid due to the electron-withdrawing inductive effect.

Answer 1

The compound CH$_3$CHFCH$_2$COOH is the stronger acid. This is because:
- The fluorine atom in CH$_3$CHFCH$_2$COOH is more electronegative than hydrogen and pulls electron density away from the carboxyl group (-COOH) through the inductive effect. This results in the stabilization of the conjugate base (carboxylate anion, RCOO$^-$), making the release of a proton (H$^+$) easier, thus increasing the acidity.
- In contrast, CH$_2$FCH$_2$COOH has the fluorine atom further from the carboxyl group, resulting in a weaker electron-withdrawing effect. Therefore, the carboxyl group is less stabilized, making CH$_2$FCH$_2$COOH a weaker acid than CH$_3$CHFCH$_2$COOH.