Question
Fri December 28, 2012 By:
 

which one is more acidic, phenol, carboxylic acid or benzoic acid, why?

Expert Reply
Fri December 28, 2012
Phenols are less (pKa»10) acidic than carboxylic acids (pKa»5)

Figure 1.  The anion resulting from deprotonation of phenol.

 

Figure 2.  The anion resulting from deprotonation of benzoic acid.

  • In phenol, the anion formed by loss of a proton is delocalized. Resonance structures show the negative charge can be shared between the oxygen atom and three of the carbons in the benzene ring.
  • In benzoic acid, the anion is also delocalized. This time the negative charge is shared between two different oxygen atoms.
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