Question

In the caffeine extraction from an energy drink lab:

a. Why was it necessary to extract the caffeine from the energy drink? Why could we not have sublimated the energy drink directly as a solution?
b. Why did we extract the energy drink with dichloromethane, specifically, and not another organic solvent such as methanol or hexane?

Answer 1

a. Why was it necessary to extract the caffeine from the energy drink?

A: Energy drink is a homogeneous mixture containing caffeine (an alkaloid) and water. The caffeine from the energy drink can be extracted through liquid/liquid extraction. Since the caffeine compound is dissolved the water it is difficult to distill the water. It needs high temperature to distill out the water.
Therefore, it is easy to extract the caffeine into low boiling organic solvent such as dichloromethane and then distill the
dichloromethane to yield caffeine.

Why could we not have sublimated the energy drink directly as a solution?

A: Sublimation process is used when a mixture contains nonvolatile impurities. In our case, we have energy drink contains water and caffeine. Water is volatile and can't sublime to yield caffeine.

b. Why did we extract the energy drink with dichloromethane, specifically, and not another organic a solvent such as methanol or hexane?

A: Dichloromethane is high density and low boiling point organic solvent. Therefore, after the extraction, it is easy to distill the mixture
to get the caffeine. Whereas, Methanol is soluble in water and there is no clear separation of organic and aqueous phases for the extraction process. So, methanol is not a good solvent for the extraction of caffeine.

The boiling temperature of hexane is also high when compared to dichloromethane. Furthermore, the solubility of caffeine is less in the hexane compared to dichloromethane. Therefore, for the extraction of caffeine dichloromethane is the best solvent.