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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