JEE MainChemistryGeneral Organic Chemistry
Match List I with List II. List I (Compound) List II ( pK_a value) (P) 4 -cyanophenol (1) 7.95 (Q) 3 -cyanophenol (2) 8.61 (R) 3 -methoxyphenol (3) 9.65 (S) 4 -methoxyphenol (4) 10.20 Choose the correct answer from the options given below:
Options
- A(P)-(1), (Q)-(2), (R)-(3), (S)-(4)
- B(P)-(4), (Q)-(3), (R)-(2), (S)-(1)
- C(P)-(2), (Q)-(1), (R)-(4), (S)-(3)
- D(P)-(1), (Q)-(2), (R)-(4), (S)-(3)
Correct answer
A. (P)-(1), (Q)-(2), (R)-(3), (S)-(4)
Step-by-step solution
The acidic strength of substituted phenols depends on the stability of the phenoxide ion formed after losing a proton. Electron withdrawing groups (EWG) stabilize the phenoxide ion and increase acidity, whereas electron donating groups (EDG) destabilize it and decrease acidity. The pK_a value is inversely proportional to acidic strength. For (P) 4 -cyanophenol, the -CN group is at the para position and exerts both strong -M and -I effects, making it the most acidic. For (Q) 3 -cyanophenol, the -CN group is at the m