Question

which necessarily requires more manipulations, the repeated extraction of an aqueous solution of cafeine with diethy ether or with dichloromethane? Why?

Answer 1

Answer: The most efficicient method for the extraction of Caffine from tea is using diethyl ether as solvent than Dichloromethan. The efficiency of extraction of diethyl ether is about 6.9% while Dichloromethan gives only 1.3% of caffine in it. Since density of diethyl ether is lesser than water it will form a layer of extracted material over it while most of cholrinated solvents such as dichloroethan having the density greater than water hence have the greater chances to remain in water only.

During extraction process the layer above water i.e. diethyl ether get seperated easily while heavier solvent may get misibled with water and it become difficult to seperate the compound from it. hence more manipulations are done with the solvent mixed with water than the solvent having less density than water. Since diethyl ether is lighter than water, get easily evaopated when open at room temperature while evaporation is not possivle in case of heavier solvents. More treatents or methods required to seperate the compound of interest from the water miscible solents.

This is the reason why more manipulations needed in case of dichloromethane as solvent than diethylether.