Which of the following is correct decreasing order of acidic strength for the compounds listed below? I: p-chlorophenol, II: p-Cresol, III: p-nitrophenol, IV: p-methoxyphenol.

Step-by-step solution

Acidic strength of phenols is directly proportional to the stability of the phenoxide ion formed after losing a proton. Electron-withdrawing groups stabilize the phenoxide ion through -I and -R effects, thereby increasing the acidic strength. Electron-donating groups destabilize the phenoxide ion through +I , +H , and +R effects, thereby decreasing the acidic strength. In p-nitrophenol (III), the -NO₂ group exerts strong -R and -I effects, making it the most acidic. In p-chlorophenol (I), the -Cl group exerts a -I