Question

Salicylic acid is prepared from phenol by:
A. Reimer-Tiemann reaction
B. Kolbe's reaction
C. Kolbe-electrolysis reaction
D. None of the above

Answer 1

Hint: Reaction of phenol with carbon tetrachloride in aqueous sodium hydroxide gives salicylic acid as the major product.
It is called the Reimer-Tiemann reaction.

Complete step-by-step answer:
In the reaction of phenol with carbon tetrachloride in aqueous sodium or potassium hydroxide, salicylic acid is the product.
This reaction occurs at 340 K temperature.
The IUPAC name of Salicylic acid is 2-hydroxybenzoic acid.
The mechanism of the reaction is as follows:
It is an electrophilic substitution reaction.
The first step involves the removal of the proton from phenol in aqueous sodium hydroxide giving sodium phenoxide as the product.



Image: Sodium phenoxide ion formation
The next step involves the attack of carbon tetrachloride at the ortho position of the benzene ring.
This leads to the replacement of three chlorine atoms with three hydroxide ions.
The removal of a molecule of water happens in the following step.
The product when reacted with aqueous sodium hydroxide followed by dilute hydrochloric acid forms 2-Hydroxybenzoic acid or salicylic acid.



Image: Formation of salicylic acid from sodium phenoxide ion.

So, option A is correct.

Additional Information: Reaction of phenol with chloroform in aqueous sodium or potassium hydroxide at temperature 340 K then hydrolysis of the resulting product forms 2-hydroxybenzaldehyde or salicylaldehyde as the primary product.

Note: Reimer-Tiemann reaction is the production of salicylic acid and salicylaldehyde using phenol as the reactant.
For the formation of salicylic acid, carbon tetrachloride is used as a reagent and for salicylaldehyde, chloroform is used as a reagent.