Question

Although phenoxide ion has more number of resonating structures than benzoate ion, benzoic acid is a stronger acid than phenol. Why ? 

Answer 1

The resonating structure of phenoxide is given as below :

Resonating structure of phenoxide ion

In resonating structure of phenoxide, negative charge is present on C-atom (which is less electronegative) while in benzoate ion, negative charge is present on more electronegative atom. Hence, in ionic structure, if negative charge is present on more electronegative atoms, therefore it is more stable in comparison to that ion which have negative charge on less electronegative atoms.

Thus, due to higher stability of benzoate ion, it is able to provide more H⁺, so it is more acidic.

So, order of acidic strength C₆H₅COOH > C₆H₅OH