Salicylaldehyde is synthesized from phenol, when reacted with
- HCl, NaOH
- CO2 , NaOH
- CCl4 , NaOH
The Correct Option is D
Approach Solution - 1
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:
\(\text{Phenol} + \text{Chloroform} \xrightarrow{\text{NaOH}} \text{Salicylaldehyde}\)
Approach Solution -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.
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