Question

Most phenols (ArOH) do not react with sodium bicarbonate solution but do react with sodium hydroxide solution. Describe how to separate, by extraction, a mixture of a water-insoluble

phenol (ArOH) and a water-insoluble carboxylic acid (RCOOH).

Answer 1

The following are the steps to separate RCOOH and ArOH:-

1) To an aqueous solution of this mixture(note both are insoluble in water) add sodium bicarbonate(NaHCO3). It only reacts with the carboxylic acid, converting it to its conjugate base RCOO- which dissolves readily in the aqueous water layer. It can be heated and evaporated to get extracted as the sodium salt of the acid.

RCOOH +. HCO3- . ----> . RCOO- . +H2CO3

2) Now the rest of the ArOH can be reacted with NaOH to form it's particular conjugate ArO- which again dissolves in water which can later be extracted to get the sodium salts of this phenol.

ArOH . + . OH- . ---->ArO- + . H2O.