Question

Phenol with \[{\text{CC}}{{\text{l}}_{\text{4}}}\] and \[{\text{KOH}}\] gives salicylic acid. The reaction is known as:
(A) Friedel-Craft reaction
(B) Reimer - Tiemann reaction
(C) Rosenmund's reaction
(D) Siemlet reaction

Answer 1

Hint: Out of the given options, identify the reaction that introduces a carboxylic functional group in the aromatic ring. For each reaction, identify which functional group is transformed which functional group.

Complete step by step answer:
A Friedel-Craft reaction introduces either alkyl or acyl groups in the aromatic ring. The reagent is alkyl halide or acyl halide, the substrate is an aromatic ring and the Lewis acid catalyst is anhydrous aluminium chloride.
Rosenmund's reaction reduces acid chlorides to aldehydes. The reagent is hydrogen gas in presence of palladium catalyst partially poisoned with barium sulphate.
The reaction of phenol with carbon tetrachloride in presence of potassium hydroxide forms salicylic acid. You can call this reaction the Reimer - Tiemann reaction.
\[{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}} - {\text{OH }}\xrightarrow{{{\text{CC}}{{\text{l}}_{\text{4}}}{\text{ KOH}}}}{\text{ o}} - {\text{HO}} - {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{4}}} - {\text{COOH}}\]
Here \[{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}} - {\text{OH}}\] represents phenol whereas \[{\text{ o}} - {\text{HO}} - {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{4}}} - {\text{COOH}}\] represents salicylic acid. Salicylic acid is also called ortho hydroxy benzoic acid. In this reaction a carboxylic functional group is introduced in the aromatic nucleus.
In the above reaction, you will obtain the ortho isomer as the major product. This is due to resonance stabilization and presence of intramolecular hydrogen bonding.

Hence, the correct option is the option (B) Reimer - Tiemann reaction.

Note: In organic synthesis, functional group transformation is used to convert one functional group into another functional group with the help of proper reagents. Certain functional group transformations are called as name reactions. The reactions given in the options are different examples of name reactions.