Ethers are relatively inert compounds;
however, under specific conditions they do undergo the following types of reactions :
Reactions involving the oxygen atom of ether
Reactions involving the cleavage of C−O bond in ether
Reactions involving the alkyl group of ether
Electrophilic substitution reactions in aromatic ethers
Reactions of Ethers Involving the Oxygen Atom
Ethers behave as Lewis bases because of the presence of two lone pairs on oxygen atom and thus dissolve in cold concentrated
acids to form stable oxonium salts.
Also, being lewis bases, ethers form coordinate compounds, known as etherates, with lewis acids such as
BF3, AlCl3, Grignard reagents etc.
Electrophilic Substitution Reaction
The alkoxy group (-OR) is ortho para directing and activates the aromatic ring towards electrophilic substitution reaction in the
same way as in phenol. Ethers, however, are less reactive than phenols towards electrophilic substitution reaction.
Reactions Involving Alkyl Group; and Cleavage C-O
The alkyl group of ether is also responsible for many reactions. The most common one is the action of air and light on ethers that
results in the formation of peroxides. The C-O bond in ethers does not get cleaved easily, and hence, the reactions involving the
cleavage of C-O bond take place under drastic conditions.
We are done with the conceptual part. We will study the reactions from next page onwards.
Question : Explain why ortho-nitrophenol is more acidic than ortho-methoxyphenol?
Answer : In o-nitrophenol, because of -R and -I-effect of -NO2 group, electron
density on oxygen in O-H bond decreases that causes O-H bond to break easily.
-I-effect in o-nitrophenol
-R-effect in o-nitrophenol
In contrast, due to +R-effect of the OCH3 group, the electron density on oxygen in the O-H bond increases
;therefore, the release of proton becomes difficult.
+R-effect in o-methoxyphenol
Hence, o-nitrophenol is more acidic than o-methoxyphenol.