Why are ethers not soluble in water

 
Occurrence

Substances from the group of ethers occur naturally in essential oils: Anethole is the main component of the anise oil obtained from the aromatic plant anise. It is used as a fragrance in soaps or as a flavoring in aniseed liqueur. Estragole is obtained from the spice tarragon. Eugenol is the main ingredient in clove oil.





Functional group

The word ether (obsolete ether) is from the Greek word aither derived, which means something like "upper air" or "fire air". The word often refers to diethyl ether, which was previously used as an anesthetic. The term is used in chemistry today Ether an organic group of substances in whose molecules an oxygen atom with two organic radicals according to the general formula R.1-O-R2 connected is. In diethyl ether, two ethyl radicals are attached to the oxygen atom. There are also ring-shaped ethers such as the solvents tetrahydrofuran (THF) and dioxane:
   
   
Aliphatic ether Cyclic ether Cyclic ether



   
Diethyl etherTetrahydrofuran1,4-dioxane
  
   
properties 
  

Diethyl ether and butanol have the same empirical formula, but different structural formulas and functional groups. One speaks therefore of a function isomerism. In contrast to an alcohol such as ethanol, the ethers are not water-soluble because they do not form hydrogen bonds. Therefore, their boiling points are also lower than those of the corresponding alcohols. They are not attacked by alkalis and diluted acids. Nitric acid and oxidizing agents oxidize the ethers. Explosive ether-air mixtures are formed with air. When standing in the air or with oxygen for a long time, they react to form explosive peroxides. The ethers have a narcotic effect and can be recognized by their typical ether odor.

  
  
Manufacturing 
  

Several processes are important for the preparation of the ethers. If you heat excess ethanol with sulfuric acid to around 130 ° C, an acid-catalyzed condensation of two ethanol molecules produces diethyl ether and water:

  

  
  

A similar reaction also takes place at about 300 ° C on the aluminum oxide contact. But then the yield is lower. In the Williamson synthesis, an alkali metal alcoholate such as sodium methylate is reacted with a haloalkane such as iodomethane. A wide variety of ethers can be produced depending on the alcoholate and alkyl group. In the example shown, dimethyl ether and sodium iodide are formed:

CH3ONa + CH3I. CH3-O-CH3 + NaI
  
  
use 
  
In the laboratory, ethers are important solvents for extractions. However, due to the potential danger of explosion, they are now often replaced by other agents. Its use as an anesthetic is no longer widespread either. Aromatic ethers are used as aromas and fragrances.



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