Chapter 11, Problem 1Q

Interpretation Introduction

Interpretation:

Theoutline of a separation scheme for isolating caffeine from tea needs to be explained.

Concept Introduction:

In the isolation of caffeine from tea leaves, the main problem is that the caffeine is not the only natural substance present in the tea leaves, but there are other substances as well from which it needs to be separated. The main component is cellulose which is polymer of glucose and it is insoluble in water. Due to the insolubility in water it causes no problem in the isolation method. Caffeine is water soluble; it is present as 5% by weight of the tea leaves.

  

Answer to Problem 1Q

Explanation of Solution

Caffeine is mainly extracted from tea leaves. There are certain steps of isolation which includes extraction and purification of caffeine from tea. The flow chart is as given below:

  

According to the above flow chart, tea leave from the tea bags are boiled and extracted with water. After that 0.5 g of

  ${\text{CaCO}}_{\text{3}}$ is added to the extracted tea. The salted tea is then extract with ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ which results in the formation of caffeine along with ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ and water. The obtained solution is then dried with ${\text{MgSO}}_{\text{4}}$ to give mixture of caffeine and ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ which is further evaporated using the dry solvent to give pure caffeine.

Conclusion

Thus, theseparation scheme for isolating caffeine from tea is represented as follows: