NEETChemistryGeneral Organic Chemistry
Assertion (A) : pKa of phenol is 4.19 and that of benzoic acid is 10 Reason (R) : Phenoxide ion is stabilised by nonequivalent resonance structures whereas benzoate ion by two equivalent resonance structures The correct option among the following is
Options
- AA and R are true. R is the correct explanation of A
- BA and R are true, but R is not the correct explanation for A
- CA is true R is false
- DA is false but R is true
Correct answer
D. A is false but R is true
Step-by-step solution
pK _ a =- K _ a so as K _ a increases, pK _ a decreases. Benzoic acid is a stronger acid than phenol so its pK _ a will be smaller than that of phenol. Thus, Assertion (A) is false. The resonance structures of phenoxide ion and benzoate ion are given by:- Thus, Reason (R) is true.