Question

Salicylaldehyde is synthesized from phenol, when reacted with

• A. HCl, NaOH
• B. CO₂ , NaOH
• C. CCl₄ , NaOH
• D.

  

Answer 1

The Correct Option is D

The synthesis of salicylaldehyde from phenol can be achieved through the reaction of phenol with HCl and NaOH in a method known as the Reimer-Tiemann reaction. Here’s how the reaction proceeds:

Reimer-Tiemann Reaction: In this reaction, phenol is treated with chloroform in the presence of a strong base (usually NaOH) and HCl is used for the acidic work-up.

The phenol undergoes electrophilic substitution, resulting in the ortho- and para-formylation of the aromatic ring.

Reaction Overview: The reaction mechanism involves:

• Formation of a phenolate ion from phenol when treated with NaOH. The nucleophilic phenolate ion attacks the carbon of the chloroform molecule, followed by hydrolysis to yield salicylaldehyde.

Final Product: The final product is salicylaldehyde, which can be represented as follows:

\(\text{Phenol} + \text{Chloroform} \xrightarrow{\text{NaOH}} \text{Salicylaldehyde}\)

Answer 2

Salicylaldehyde is synthesized from phenol. The correct reagents for this synthesis must be identified from the given options.

Concept Used:

The Reimer-Tiemann reaction is a key organic conversion used to synthesize ortho-hydroxybenzaldehydes (such as salicylaldehyde) from phenols. The reaction involves the treatment of phenol with chloroform (CHCl₃) in the presence of a strong base like sodium hydroxide (NaOH).

Step-by-Step Solution:

Step 1: Identify the target compound and the starting material. The target is salicylaldehyde (2-hydroxybenzaldehyde), and the starting material is phenol.

Step 2: Recall the standard reagent combination for the Reimer-Tiemann reaction. The reagents are chloroform (CHCl₃) and a strong base (NaOH).

Step 3: Compare the standard reagents with the given options.

Option (1): HCl, NaOH - This is not the correct combination for introducing an aldehyde group.

Option (2): CO₂, NaOH - This is the Kolbe-Schmitt reaction, which produces salicylic acid, not salicylaldehyde.

Option (3): CCl₄, NaOH - This can produce salicylic acid under specific conditions, not the aldehyde.

Option (4): HCCl₃, NaOH - This represents chloroform (CHCl₃) and sodium hydroxide, which is the exact reagent combination for the Reimer-Tiemann reaction.

Therefore, salicylaldehyde is synthesized from phenol using the reagents in Option (4): HCCl₃, NaOH.