Question

If we use carbon tetrachloride (\[CC{l_4}\]​) in the Riemer - Tiemann reaction in place of chloroform, the product formed is:
A. Salicylaldehyde
B. Phenolphthalein
C. Salicylic Acid
D. Cyclohexanol

Answer 1

Hint: The Riemer-Tiemann reaction involves the ortho-formylation of phenol. It takes place in the presence of chloroform and a strong hydroxide base. Under such conditions, phenol is converted into salicylaldehyde.

Complete Step by Step Solution:
The Riemer-Tiemann reaction is a chemical reaction in which phenol gets converted to salicylaldehyde. This occurs when phenol is reacted with chloroform (\[CHC{l_3}\]) in the presence of a strong base such as sodium hydroxide (\[NaOH\]) or potassium hydroxide (\[KOH\]).

Image: Formation of Salicylaldehyde

However, the Riemer-Tiemann can be modified to produce phenolic acids such as salicylic acid by using carbon tetrachloride (\[CC{l_4}\]) instead of chloroform.

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

The reaction proceeds in the following way.

First, the \[NaOH\] abstracts the acidic proton from phenol to give a phenoxide ion. The negative charge in the oxygen atom gets dispersed into the ring through the +R effect making the ring more nucleophilic.

Image: Step 1: Abstraction of proton
The nucleophilic ring then attacks the electrophilic carbon atom of\[CC{l_4}\].

Image: Step 2
Each of the three chlorine atoms is removed by the sodium hydroxide leaving behind three hydroxyl groups attached to the carbon atom as shown here.

Image: Step 3
The product formed above undergoes spontaneous dehydration followed by acidic hydrolysis to give us the final product i.e., salicylic acid.

Image: Step 4

Thus, option C is the correct option.

Note: It must be remembered that the reaction mentioned above is only a variation of the Riemer-Tiemann reaction. The actual Riemer-Tiemann reaction leads to the formation of salicylaldehyde from phenol.

Image: Riemer-Tiemann reaction of phenol.