Question

Synthesis of Acetaminophen

A) Why should you use a minimum amount of a boiling solvent when recrystallizing the crystals of the acetaminophen? Explain.

B) Why should you use a minimum amount of a very cold solvent when washing the crystals of the acetaminophen? Explain.

Answer 1

Answer for question (A):

During recrystallization of any organic compound such as acetaminophen one needs to use minimum amount of boiling solvent. It's because more sample (acetaminophen) will be dissolved in a boiling solvent and when we use minimum amount of solvet it reaches saturation quickly at boiling temperature. When the solvent is cooled, since it's already saturated at boiling temperature, the sample will crystallize out as soon as the solvent is started cooling to room temperature.

Answer for question (B):

The crystals of any organic compound (such as acetaminophen) need to be washed with minimum solvent. Otherwise the compound may get dissolved in the solvent and we might lose large amount of compound into the solution and thus leaving fewer crystalline compound.

Further it's advisable to use a washing solvent which dissolves the compound sparingly. As can be seen from the above question the temperature plays an important role in the solubility of a substrate in a solvent. It's advisable to use minimum amount of cooled solvent for washing the crystals of a compound such as acetaminophen.