Both alcohols and phenols contain a hydroxyl group, but phenols are more acidic than alcohols. The reason being that the phenoxide ion left after the removal of a proton is resonance stabilized while alkoxide is not. Therefore, phenols dissolve in aqueous sodium hydroxide but alcohols do not. However, both are weaker acids than carbonic acid and hence do not decompose aqueous `NaHCO_(3)` solution evolving `CO_(2)`. The presence of electron-donating groups in the benzene ring decrease the acid strength while the presence of electron withdrawing groups in the benzene ring increase the acid strength of phenols. The relative strength of o-, m- and p- substituted phenols, however, depends upon a combination of inductive and resonance effects of the substituent.
Alcohols are very weak acids even weaker than water. Because of the `+I` effect of the alkyl groups, tha acidic strength of alcohols decreases in the order : `1^(@)` alcohol `gt 2^(@)` alcohol `gt 3^(@)` alcohol.
Which of the following is the strongest acid
A. o-Fluoro phenol
B. o-chloro phenol
C. o-Bromo phenol
D. o-Iodo phenol
