Question

why we use NaOH and brine during the extraction(purification of product) in the synthesis of phenacetin from acetaminophen

Answer 1

Step (1):- In the synthesis of phenacetin from acetaminophen, we need to use NaOH which is strong base to remove or quench the extra or excess acid present in the separating funnel which contains the aqueous (water) as well as the organic layer. And finally extract the organic layer from the aqueous layer with the ethyl acetate three times.

Step (2):- After extraction from the aqueous layer, that organic layer must contains some bulk water within it. To remove that bulk water from the organic layer, we need to wash with the brine (saturated solution of sodium chloride in water) that organic layer two to three times. After washing with the brine, add the Na₂SO₄ into that organic layer to absorb the remaining water and evaporate it by rota vapor and purify by the column chromatography to get the pure compound.