Question

Among alcohols and phenols which one is more acidic and why?

Answer 1

Phenol is more acidic than alcohol.
The $-OH$ group of alcohol is attached to $s{p}^3$ hybridized carbon. The $-OH$ group of phenol is attached to $s{p}^2$ hybridized carbon. $s{p}^2$ hybridized carbon is more electronegative than $s{p}^3$ hybridized carbon. This decreases electron density on oxygen in phenol. The $O-H$ bond polarity increases which increase ionization in phenol. Also, in alkoxide ion, the negative charge is localized on oxygen while in phenoxide ion, the negative charge is delocalised. Hence, phenoxide ion is more stable than alkoxide ion.
Note: Charge is also delocalized in phenol, but its resonance structures have charge separation due to which phenol is less stable than phenoxide ion.