An amino-naphthol derivative couples with a diazonium salt ArN_2^ + X^ - at pH 5-7 to give X, and with the same diazonium salt at pH 8-10 to give Y. X and Y are, respectively

JEE Main Chemistry question

An amino-naphthol derivative couples with a diazonium salt at pH 5-7 to give , and with the same diazonium salt at pH 8-10 to give . and are, respectively

(A)two regiochemically distinct azo-coupling products: coupling occurs at the position activated by the free group at pH 5-7, and at the position activated by the phenoxide () ion at pH 8-10Correct
(B)the same single azo product at both pH values, since and always activate the same ring position
(C)no coupling at all at either pH, since amino-naphthols do not undergo diazo coupling
(D)-arylation (an aryl ether) at pH 5-7, and azo coupling only at pH 8-10

Answer: (A)

Solution

This amino-naphthol has two activating groups ( and ) that compete to direct the incoming diazonium electrophile. At the lower pH (5-7), the amino group (not yet converted to the far more powerful phenoxide) is the dominant director, so coupling () occurs at the position it activates. At the higher pH

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Question ID VK-150364