Question

Which acid of the pair shown here would you expect to be stronger?

CH₃CO₂H or CH₂FCO₂H

Answer 1

It is difficult for the proton to escape because the +I effect of −CH3 group increases the electron density in the O–H bond.	The release of the proton is easy because the −I effect of −F reduces the electron density in the O–H bond.
The +I effect due to the concentration of negative charge destabilises the carboxylate ion.	The spreading of the negative charge causes the –I effect to stabilize the carboxylate ion.

Hence, due to lower electron density in the O–H bond and higher stability of FCH₂COO^– ion, FCH₂COOH is a stronger acid than CH₃COOH.