Glycol

Ethylene Glycol

Ethylene Glycol, (CH2OH)2, contain two hydroxyl groups in the molecules, and is a dihydric alcohols, also called diols or glycols.

Dihydric alcohols are usually prepared by the oxidation of an alkene with potassium permanganate.

Preparation of Ethylene Glycol

Ethylene glycol can be readily prepared in the laboratory by refluxing ethylene dichloride with a dilute solution of sodium carbonate.


					Na2CO3  
		CH2Cl           ==>             CH2OH   
		CH2Cl                           CH2OH   
		Ethylene                                Ethylene        
		Dichloride                              Glycol

Manufacture of Ethylene Glycol

A commercial method for preparing ethylene glycol involves the oxidation of ethylene to ethylene oxide and the subsequent hydrolysis of this oxide, over a silver catalyst at 250 degC to ethylene glycol.


                       CH2=CH2  +  (O2  ==>    CH2 CH2            CH2CH2  
                           			     O                  OH OH   
                        Ethylene                        Ethylene             Ethylene        
				Oxide                 Glycol

The three membered ring in ethylene oxide which is formed initially in the reaction, is very reactive. Ethylene oxide readily reacts with water to yield ethylene glycol (as above) or with ammonia to give ethanolamine (as below).


		CH2CH2  +  NH3  ==>     CH2CH2  
		     O                                 OH NH2  
		Ethylene                        Ethanolamine    
		Oxide

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