Question

An azo dye is fixed on fabrics by the process applicable in

• A. Vat dyes
• B. Mordant dyes
• C. Developed dyes
• D. Substantive dyes

Hint:

Azo dyes are often formed directly on fabric by diazotization and coupling; this is called developed dyeing.

Answer 1

The Correct Option is C

Concept:
Azo dyes contain the azo group: \[ -N=N- \] They are commonly formed by diazotization followed by coupling reaction. In developed dyeing, the dye is produced directly on the fabric.

Step 1: Understand azo dye formation.
Aromatic amines are first converted into diazonium salts. Then diazonium salts undergo coupling with phenols or aromatic amines. This forms azo dyes: \[ Ar-N=N-Ar' \]

Step 2: Understand developed dyes.
In developed dyes, the final dye is formed inside or on the fibre itself. This helps the dye fix strongly on the fabric. Azo dyes are commonly fixed by this process.

Step 3: Check the options.
Option (A) Vat dyes involve insoluble dyes reduced to soluble form and then oxidized on fibre.
Option (B) Mordant dyes require mordants like metal salts.
Option (C) Developed dyes is correct because azo dye is developed on the fabric.
Option (D) Substantive dyes directly attach to fibre but are not the specific answer here. Hence, the correct answer is: \[ \boxed{(C)\ \text{Developed dyes}} \]