Why do aqueous solutions of phenol give acidic solutions?

1 Answer
anor277
Jul 31, 2017

You've got phenol, C_6H_5OH.....?

Explanation:

Because the "phenoxide anion" is stabilized somewhat by resonance, and delocalization of charge density, "phenol", and its derivatives are mildly acidic......

C_6H_5OH(aq) + H_2O(l)rarrC_6H_5O^(-) +H_3O^+

or since you specified an "Arrhenius acid".........

C_6H_5OH(aq) stackrel(H_2O)rarrC_6H_5O^(-) +H^+

pK_a=8.00

Substitution of the ring by nitro groups that cause the charge density of the anion to DECREASE, causes the acidity to increase. "1,3,5-trinitrophenol", 1,3,5-(O_2N)_3C_6H_2OH is otherwise known as "picric acid", whose pK_a=0.38, very strong for a carbon acid.

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