The increasing order of acidic strength among p-methoxyphenol, p-cresol and p-nitrophenol is (a) p-cresol \(<\) p-methoxyphenol \(<\) p-nitrophenol (b) p-methoxyphenol \(<\) p-cresol \(<\) p-nitrophenol (c) \(\mathrm{p}\) -cresol \(<\mathrm{p}\) -nitrophenol \(<\mathrm{p}\) -methoxyphenol (d) p-methoxyphenol \(<\) p-nitrophenol \(<\mathrm{p}\) -cresol

First, let's identify the conjugate bases of each compound after losing a proton from the phenolic hydroxyl group (OH). Remember that the more stable the conjugate base, the stronger the corresponding acid. p-methoxyphenol: \(\mathrm{OCH}_3\) p-cresol: \(\mathrm{CH}_3\) p-nitrophenol: \(\mathrm{NO}_2\)

Now, let's analyze how each substituent group influences the stability of the conjugate base. \(\mathrm{OCH}_3\): This group has a lone pair of electrons on the oxygen atom, which exhibits a +M(electron-supporting) effect through resonance with the conjugate base. This will make phenoxide ion less stable, decreasing the acidity of the compound. \(\mathrm{CH}_3\): This group is a weak +I(inductive) effect donor, which slightly destabilizes the conjugate base and lowers the acidity. \(\mathrm{NO}_2\): This group exhibits a -M(electron-withdrawing) effect through resonance and a -I(electron-withdrawing) effect inductively, having a significant stabilizing effect on the conjugate base. Hence, it increases the acidity of the compound.

Comparing the electronic effects concluded in Step 2, we can establish the correct order of acidic strength: p-cresol (weakest, only +I effect) p-methoxyphenol (intermediate, +M effect outweighs inductive effect) p-nitrophenol (strongest, -M and -I effect) The increasing order of acidic strength is: p-cresol \(<\) p-methoxyphenol \(<\) p-nitrophenol So, the correct answer is (a).