In general, acidic organic compounds are
extracted with an aqueous inorganic base suc as NaOH. NaOH is
a strong inorganic base and both benzoic acid (a carboxylic acid)
and 2-naphthol (a weak acid) are ionized to a salt in the presence
of NaOH.
Benzoic Acid
C7H6O2
pKa:
4.18
2-naphthol
C10H8O
pKa:
9.57
Reference: G. Marc Loudon, Organic
Chemistry, 3rd ed., Benjamin/Cummings Publishing Co, Inc,