Phenoxide ion generated by treating phenol with sodium hydroxide is even more reactive than phenol towards electrophilic aromatic substitution. Hence, it undergoes electrophilic substitution with carbon dioxide, a weak electrophile. Ortho hydroxybenzoic acid is formed as the main reaction product.
Heating the nucleophilic phenolate salt with carbon dioxide under high pressure / temperature results in regioselective ortho-substitution.
This process is also known as the Kolbe-Schmitt synthesis.
o-hydroxybenzoic acid is more commonly known as salicyclic acid.
On treating phenol with chloroform in the presence of sodium hydroxide, a –CHO group is introduced at ortho position of benzene ring. This reaction is known as Reimer - Tiemann reaction. The intermediate substituted benzal chloride is hydrolysed in the presence of alkali to produce salicylaldehyde.
Write the main product in the following reactions.