Sodium carbonate (Na2CO3
)- This is a base which deprotonates the phenolic OH
of tannins, rendering these compounds anionic and hence highly soluble
in water but with a low solubility in the methylene chloride.
vi
If Na2CO3
was not present the isolated caffeine would also contain extracted tannins.
Methylene Chloride- CH2
Cl2
, This is also called dichloromethane. This is a
halogenated organic solvent. This is used in the liquid-liquid extraction
portion of the experiment. The caffeine is extracted from the water solvent
to the CH
2
Cl2
due to a favorable distribution coefficient.