9.0 Chemical Properties of Ethers

1.Salt formations: When ethers are treated with cold concentrated inorganic acids, these form oxonium salts. The reaction between ethers and acid is a Lewis acid-base type interaction.

2. Action of air and light: Reaction involving alkyl group leads to the formation of peroxides.

It is a free radical reaction and oxidation occurs at the C atom next to the etheral oxygen to form hydroperoxides.

3. Halogenation of Ether: When treated with chlorine or bromine, ethers undergo substitution, the extent of which depends on the conditions. Hydrogen joined to the carbon directly attached to the oxygen atom is most readily replaced, e.g. diethyl ether reacts with chlorine in the dark to from 1,1-dichlorodiethyl ether:

The reaction proceeds by a free-radical mechanism, and a-substitution occurs readily because of resonance stabilization of the intermediate radical.

4. Reaction with Acid Chlroides: Acid chlorides react with ethers when heated in the presence of anhydrous zinc chloride, aluminium chloride, etc.; e.g.

Acids anhydrides also split ethers to form esters:

\[{R_2}O + {(C{H_3}CO)_2}O\xrightarrow{{ZnC{l_2}}}2C{H_3}C{O_2}R\]

5. Cleavage by Acids: Ethers on reaction with acids (HX) in presence of heat undergoes cleavage to form an alkyl halide and an alcohol. Alcohol on further reaction with HX gives second molecule of alkyl halide.

\[R-O-R' + {\text{ }}HX \to R-X{\text{ }} + R'-O-H\]