Question

Salicylic acid can be prepared using Reimer - Tiemann’s reaction by treating phenol with:
A. Methyl chloride in the presence of anhydrous aluminium chloride
B. Carbon dioxide under pressure in sodium hydroxide solution
C. Carbon tetrachloride and concentrated sodium hydroxide
D. Sodium nitrite and a few drops of concentrated sulphuric acid

Answer 1

Hint: The Riemer-Tiemann reaction involves the ortho-formylation of phenol. In essence, it is a nucleophilic substitution reaction.

Complete Step by Step Solution:
The Riemer-Tiemann reaction is used for the ortho-formylation of phenols using a strong base in the presence of carbon tetrachloride (\[CC{l_4}\]). The strong base most commonly used is concentrated sodium hydroxide (\[NaOH\]) or potassium hydroxide (\[KOH\]).
While phenol is soluble in carbon tetrachloride, the hydroxide base is not. Therefore, this reaction is generally carried out in a solvent system that has two phases (biphasic). In its simplest case, the biphasic system consists of an aqueous phase containing the hydroxide base and an organic phase containing the carbon tetrachloride and phenol. The two phases are brought together (by rapid mixing or by using phase transfer catalysts) and heated to initiate the reaction. Although heating is required to start the reaction, once it is underway the reaction itself becomes highly exothermic.

The Riemer-Tiemann reaction of phenol with\[CC{l_4}\]and concentrated sodium hydroxide leads to the formation of salicylic acid as the product.

Image: Conversion of phenol into salicylic acid through Riemer-Tiemann reaction

Thus, the correct option is C.

Note: Although the reaction discussed above is termed as a Riemer-Tiemann reaction, it is a variation of it. The actual Reimer-Tiemann reaction consists of the reaction of phenol with chloroform (\[CHC{l_3}\]) and a strong hydroxide base to form salicylaldehyde as shown below.

Image: Riemer-Tiemann reaction of phenol.