1. Kolbe’s reaction:
When phenol is treated with sodium hydroxide, sodium phenoxide is produced. This sodium phenoxide when treated with carbon-di-oxide, followed by acidification, undergoes electrophilic substitution to give o-hydroxipenzoic acid as the main product. This reaction is known as Kolbe’s reaction.
2. Reimer-Tiemann reaction:
When phenol is treated with chloroform (CHCl3) in the presence of sodium hydroxide, a – CHO group is introduced at the ortho position of the benzene ring.
This reaction is known as the Reimer - Timann reaction.
The intermediate is hydrolyzed in the presence of alkalis to produce salicyclal dehyde.
3. Williamson ether synthesis:
Williamson ether synthesis is a laboratory method to prepare symmetrical and unsymmetrical ethers by allowing alkyl halides to react with sodium alkoxides.
R-X + R- ONa → R-O-R + NaX
This reaction involves SN2 attack of the alkoxides ion on the alkyl halide. Better results are obtained in case of primary alkyl halides.
If the alkyl halide is 2° or 3°, then elimination competes over substitution.
4. Unsymmetrical ether:
An unsymmetrical ether is an ether where two groups on the two sides of an oxygen atom differ (i.e., have an unequal number of carbon atoms). For e.g: ethyl methyl ether (CH3 - O - C2H5)
