Question

Which chemical reaction is used for the ortho-formylation of phenol?
A.Reimer-Tiemann reaction
B.Kolbe’s reaction
C.Williamson ether synthesis
D.Friedel – craft reaction alkylation of anisole

Answer 1

Hint:The reaction which is used for the ortho formylation of phenol uses an alkali such as sodium hydroxide and chloroform. It is a famous naming reaction.

Complete step by step solution:
Reimer Tiemann reaction is used for the ortho formylation of phenols. An alkali is used because the hydroxide group is not soluble in solvents such as chloroform because of its non polar nature. In this reaction a phenol is converted into ortho hydroxy benzaldehyde using the above mentioned reagent.
Kolbe reaction is a carboxylation reaction. Here the end product is carboxylic acid. Phenol is treated with carbon dioxide and a base such as sodium hydroxide forms phenoxide ion and then treating it with sulphuric acid forms salicylic acid. Here also no formyl group is formed.
William ether synthesis as the name suggests is a reaction for the formation of ether. It is a nucleophilic substitution reaction. An alkyl halide is treated with alkoxide ion and the ether is formed. It is also used for the cyclic ether formation. No aldehyde is formed here and so no formation is occurring.
Friedel craft reaction occurs using an alkyl halide. It is treated with anisole using the catalyst. The catalyst used is a Lewis acid such as anhydrous aluminium chloride. This helps in the generation of the nucleophile.

Hence, the correct option is A.

Note:
The formyl group basically represents an aldehyde group. The reaction is mainly used for the synthesis of salicylic acid. There are other methods for the direct formylation but Reimer tiemann reaction is best in terms of ease and safety.