Why phenol (C6H5OH) is acidic in nature?

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Phenol( C6H5OH) is an aromatic compound.In phenol OH group is attached to the benzene ring. As we define an acid is a species that ionizes its H+ (proton) easily. The acidic ability of phenol comes due to its ability to ionize H+ and production of phenoxide - phenoxide is a conjugate base of phenol and stabilizes by its resonating structures. we know that an acid will be stronger if it produces a stable conjugate base. ionization of phenol occurs by following chemical equation.

Phenol-ionization-phenoxide-formation

A phenoxide (conjugate base) is formed which is a stable ion as electrons on the oxygen is not localized on the oxygen atom alone rather become delocalized on entire benzene ring , which make the phenoxide stable and give considerable acidic property to phenol.

Phenoxide-conjugate-structures


Phenol is recognizably acidic can be justify by reaction of phenol( C6H5OH) with sodium hydroxide (NaOH). Phenol is weak acid and NaOH is strong base this reaction gives sodium phenoate (salt) and water. this is weak acid and strong base reaction and give  sodium phenoate or phenoxide ( basic salt) , this acid base reaction justify phenol as acid.

Phenol-weak-acid-strong-base-reaction


But keep remember that still phenol is a very weak acid as equilibrium position lie enough to left. Oxygen atom of phenoxide is highly electronegative the delocalized electron will well drawn towards the oxygen atom  so, oxygen atom has strong ability to bond again the proton (H+).


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