When benzene diazonium chloride reacts with phenol, it results in the formation of an orange colored compound (X); and when benzene diazonium chloride reacts with aniline, it results in the formation of a yellow colored compound (M). What are X and Y?

X: p-Hydroxyazobenzene; Y: p-Aminoazobenzene

The correct answer is Option (1) → X: p-Hydroxyazobenzene; Y: p-Aminoazobenzene

Benzene diazonium chloride undergoes azo coupling reactions with activated aromatic compounds such as phenol and aniline.

In an azo coupling reaction, the diazonium salt acts as an electrophile, while the aromatic ring of phenol or aniline acts as a nucleophile due to electron-donating groups.

The reaction leads to the formation of azo compounds containing the azo linkage (−N=N−).

General reaction:

Ar–N₂⁺Cl⁻ + Activated aromatic compound → Azo compound (Ar–N=N–Ar')

These azo compounds are typically highly coloured dyes.

Reaction with Phenol

Phenol contains a −OH group, which is a strong electron-donating group. It activates the aromatic ring and directs electrophilic substitution to the ortho and para positions.

However, due to less steric hindrance, the para position is favored.

Thus the major product formed is:

p-Hydroxyazobenzene

This compound appears orange in colour.

Reaction with Aniline

Aniline contains a −NH₂ group, which is also a strong activating and ortho-para directing group.

Again, due to steric stability, the para product predominates.

The product formed is:

p-Aminoazobenzene

This compound is typically yellow in colour.

Therefore:

X = p-Hydroxyazobenzene

Y = p-Aminoazobenzene

Option-wise Explanation

Option 1: X: p-Hydroxyazobenzene; Y: p-Aminoazobenzene

Phenol undergoes azo coupling mainly at the para position to form p-hydroxyazobenzene (orange dye). Aniline also couples at the para position to form p-aminoazobenzene (yellow dye). Hence this option is correct.

Option 2: X: p-Hydroxybenzene; Y: p-Aminobenzene

These structures do not contain the azo linkage (−N=N−) and therefore are not products of azo coupling reactions. Hence this option is incorrect.

Option 3: X: o-Hydroxyazobenzene; Y: o-Aminoazobenzene

Although ortho substitution is possible, it is not the major product because of steric hindrance. The para products are the dominant compounds formed. Therefore this option is incorrect.

Option 4: X: p-Hydroxyazobenzene; Y: o-Aminoazobenzene

The phenol product is correctly given as para, but the aniline product is incorrectly listed as ortho. The major product from aniline coupling is p-aminoazobenzene, not the ortho derivative. Hence this option is incorrect.