ETHERS. 303 



It is not necessary that the two hydrocarbon residues in an 

 ether should be alike, as in the above ethyl ether, but they may 

 be different, in which case the ethers are termed mixed ethers. 

 For instance : 



Methyl-ethyl ether. Propyl-amyl ether. 



In diatomic or triatomic alcohols, or in dibasic or tribasic 

 acids, containing more than one atom of hydrogen derived from 

 hydroxyl or carboxyl, these hydrogen atoms may be replaced by 

 various other univalent, bivalent, or trivalent residues. This 

 fact shows that the number of ethers or compound ethers which 

 are capable of being formed is very large. 



Formation of ethers. Ethers may be formed by the action of 

 the chloride or iodide of a hydrocarbon residue upon an alcohol 

 in which the hydroxyl hydrogen has been replaced by a metal. 

 For instance : 



Sodium Ethyl iodide. Ethyl ether. Sodium 



ethylate. iodide. 



Sodium Methyl Ethyl-methyl Sodium 



ethylate. iodide. ether. iodide. 



Ethers are also formed by the action of sulphuric acid upon 

 alcohols ; the sulphuric acid removing water in this case, thus : 



2(C 2 H 5 HO) = cS) + H >- 



Ethyl alcohol. Ethyl ether. Water. 



Compound ethers are formed by the combination of acids 

 with alcohols and elimination of water. (Presence of sulphuric 

 acid facilitates this action.) 



Ethyl alcohol. Acetic acid. Ethyl acetate. Water. 



They are also formed by the action of hydrocarbon chlorides 

 (or iodides) on salts. For instance : 



CHC1 + , KCl. 



Amyl Potassium Amyl Potassium 



chloride. formate. formate. chloride. 



