Question

For an acidic component, after treatment of a strong base the solution is then treated with a strong acid. Why is this step perfromed?

Answer 1

For an acidic component, first we have to neutralize with the strong base saturated NaOH or saturated KOH solution. In this case neutralization takes place in which, salts and water are produced. In such condition that acid component will be in water (neutral pH = 7) layer. So, it cannot be extracted further because the component will go into the water. To resolve this problem further we need to add strong acid so that it can come in acidic region (pH = 2 to pH = 3) from neutral solution region (pH = 7). Now your component is in acidic medium. After adding the organic solvent like ethyl acetate, chloroform etc. the acidic component will come into the organic layer. So, now you can easily extract the organic layer from the aqueous layer by washing with ethyl acetate 2 to 3 times. And finally add the Na₂SO₄ (to remove the excess water from the organic layer) into that organic layer and evaporate it. Final compound will be desired component.