When orthobromoanisole is treated with sodamide (NaNH₂) and ammonia (NH₃), benzyne is formed and the tripple bond is formed between C₂-C₃ carbon atoms of benzene ring. Then NH₂⁻ can attack at ortho position as well as meta position.
The reaction takes place in three steps. Step-1:The amide NH₂⁻ ion attacks the H -atom that is ortho to C3 , generating a carbanion. Step-2:Loss of Br - to form a benzyne intermediate.Step-3:Addition of NH₂⁻ ion. The strain caused by a triple bond in a benzene ring can be relieved by a nucleophilic addition of NH₂⁻.
Two isomeric products are formed: (1) o-methoxyaniline and (2) m-methoxyaniline. The structures of both the isomeric products are given in diagram.
