Question

Why are we performing the following steps in our work-up procedure for dimesitylmethane by alkylation of mesitylene with formaldehyde and formic acid as a catalyst? Please explain the reason for each of the following washings.

A) Wash the crystals with water

B) Wash with saturated aqueous sodium bicarbonate

C) Wash (again) with water

D) Wash with methanol

Answer 1

A. Wash the crystals with water:

The crystals are washed with water in order remove impurities such as dust and other aerosol particles.

B. Wash with saturated aqueous sodium bicarbonate:

At the end of this reaction there should be no formaldehyde remaining in the reaction mixture. The formic acid solvent from the reaction and aqueous washings should be combined, neutralized with sodium bicarbonate, and flushed down the drain. Mother liquor from recrystallization is placed in the organic solvents container.

C. Wash again with water:

It is to remove sodium bicarbonate.

D. Wash with methanol:

The product is to be recrystallized using organic solvent such as methanol.