strengths of phenols - hydrocarbonthe comparative

Question

Strengths of Phenols - Hydrocarbon

The comparative strengths of some phenols (as acids) are like this:

p-Nitrophenol > o-Nitrophenol > m- Nitrophenol > Phenol

Presence of electron releasing group, (e.g - CH₃, - C₂H₅, - OCH₃, -NR₂) on the benzene ring decreases the acidity of phenol like it strengthens the negative charge on phenoxy oxygen and thus proton release turns into more difficult. So, cresols are less acidic as compared to the  phenol.

Though, m-methoxy and m-aminophenols are stronger acids as compared to phenol because of -I effect and absence of +R effect.

m-methoxy phenol > m-amino phenol > phenol > o-methoxy phenol > p-methoxy phenol

Chloro phenols : o- > m- > p-

Cresols : m- > p- > o-

Dihydric phenol : m- > p- > o-