AIIMS 2018 Chemistry Acidic and Basic Strength MCQ Question

The order of acidic strength is determined by the –I (inductive) and –M (mesomeric) effects, which influence the stability of the conjugate base. In this case, the –I effect (as shown in figure IV) stabilizes the negative charge on the conjugate base more effectively than the –M effect (figure II), leading to a stronger acid. Figures III and I show zero and –M effects, respectively, which do not stabilize the conjugate base as effectively as the –I effect, resulting in a lower acidic strength. Therefore, the order IV > III > II > I reflects the decreasing stability of the conjugate bases and their corresponding acidic strengths.