Question

Coupling of benzene diazonium chloride with 1-naphthol in alkaline medium will give:

(A)

(B)

C)





D)

Answer 1

Hint: It is a type of azo coupling. In such reactions diazonium salt shows electrophilic attack on other aromatic compounds and substitution reaction occurs.

Complete Solution :
Azo coupling: Those reactions in which a diazonium compound reacts with another aromatic compound. The product of such reactions is an azo compound. These reactions come under the category of electrophilic aromatic substitution reaction, in which aryl diazonium cation behaves as electrophile and attack on activated arene which is a nucleophile.
- The given question is asking about the product of reaction between benzene diazonium chloride and 1-naphthol (alpha naphthol). So, the Product is this reaction is a dye organol brown. In this dye the electrophile aryl diazonium cation substitutes the hydrogen of at para position to the hydroxyl group of alpha naphthol among the three open positions i.e. ortho, meta, and para to the hydroxyl group.

Substitution occurs at para position of naphthol ring because of two reasons:
(1) Hydroxyl groups of phenols are ortho and para directing for electrophilic substitution reactions.
(2) In naphthalene system electrophilic substitution is kinetically favored next to the other ring.
So, among ortho and para positions, para one is next to the ring which favors the substitution at para position.

So, the correct answer is “Option C”.


Note: Organol brown is also called hex type brown, a Chemical name is 4-(Phenylazo)-1-naphthol, Chemical formula is ${{C}_{16}}{{H}_{12}}{{N}_{2}}O$.