Diethyl Ether: How Diethyl Ether is prepared
It is the dominant member of the ether class. It is also called simply ether or ethyl ether.
Read More… Diethyl Ether
Methods of Preparation
By the action of Iodoethane and dry silver oxide: Diethyl ether is obtained by heating ethyl iodide with dry silver oxide.
Williamson Synthesis Method: In this method sodium or potassium ethoxide is heated with chloro ethane, bromo ethane or iodo ethane. This reaction results in Diethyl ether.
C2H5ONa + C2H5I → C2H5 — O — C2H5 + NaI
By heating a mixture of ethyl alcohol and alumina: heating ethyl alcohol with alumina (Al2O3) at 250°C gives diethyl ether.
C2H5OH + HOC2H5 — Al2O3/250°C→ C2H5 — O — C2H5 + H2O
Laboratory Method:
By heating a mixture of ethyl alcohol and sulphuric acid: Diethyl ether is obtained by heating this mixture to about 140°C by mixing a high concentration of ethyl alcohol with slightly concentrated sulfuric acid.
C2H5OH + H2SO4 → C2H5HSO4 + H2O
C2H5HSO4 + C2H5OH → C2H5 — O — C2H5 + H2SO4
It is clear from the above reaction that a small amount of concentrated sulfuric acid taken initially can convert a very high amount of alcohol into ether. Hence this method is also called Continuous etherification method.
In practice this does not happen. Because some sulfuric acid gets reduced to form sulfur dioxide and the water concentrate in the reaction dilutes sulfuric acid. Therefore small amounts of acid are added from time to time.
About 100 ml of pure alcohol is taken in a 500 ml distillation flask. About 50 ml of concentrated sulfuric acid is slowly added to it. While adding sulfuric acid, shake the flask. Now heat the flask to 140°C by placing it on sand heat.
The ether is distilled and collected in the receptor. The receiver has a side-tube which is connected to a rubber drain and reaches the water sink. This does not allow the ether vapor to reach the burner and there is no fear of fire.
All cork in the equipment is air tight. The speed with which the ether collects in the receiver keeps pouring the alcohol into the flask from the point funnel accordingly.
Rectification: Alcohol, water and sulfuric acid are present in the form of impurities in ether obtained from the above method. To remove sulfuric acid, the obtained ether is washed with a solution of sodium dioxide.
To remove alcohol, ether is mixed with 50% calcium chloride solution and left for some time, forming crystals of CaCl2.3C2H5OH. They are filtered and separated.
To remove water, it is dried by adding anhydrous calcium chloride to the ether, thus distilling the obtained ether at 35°C to obtain pure ether.
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