Question

In the Week 4 experiment, an additional “wash” step was added to the extraction protocol. Discuss the difference between the extraction step (ethyl acetate extraction of aqueous caffeine) and the wash step (dilute base wash of the ethyl acetate layers). Your answer should mention what is happening to the caffeine and impurities in each step as well as the intermolecular forces involved in the process explain fully

Answer 1

Caffeine is an alkaloid, and having the properties of an organic amine base. It will not exist in pants alone. It will be with pigments, cellulose, and tannins (Phenolic, acidic compounds) etc.

The basic property because of the lone pair of electrons present in nitrogen. The basic property of N in caffeine can be used to increase or decrease its ability to soluble in water. In acidic conditions, it will form the conjugate acid salt giving caffeine increased water solubility as a cation. On the other hand if caffeine is in a basic environment it takes the neutral form and is only somewhat polar.

The successfully extract of any substance from one solvent into another, the differences in solubility must be maximum. So extraction of caffeine is mainly used by chloroform or dichloromethane. Ethyl acetate can be use, but the efficiency is not good as that of chloroform. So in order to increase the efficiency of ethyl acetate in extraction of caffeine, we have to add some basic condition. So the solubility of caffeine in water will decrease and solubility with ethyl acetate will increase.

The water solution contains much more than just caffeine and some of these compounds are also soluble in organic solvents. In basic condition, the basic material reacts with tannic acids to form insoluble tannin salts which precipitate and can be removed from the solution before the caffeine is extracted.

The organic extract will contain caffeine and small amounts of impurities. This solution is washed with 10% NaOH to remove impurities. Caffeine is also water soluble, but by keeping the washing solution basic it minimizes the caffeine lost, while maximizing the removal of impurities