Characteristics of reactive group of reactive dye

Characteristics of reactive group

The characteristics of reactive group of dye are mentioned below:

1)    Reactive groups do not contribute to the color of dye. Chromogen group imparts it.

2)    The reactivity of vinyl sulphone group is less than that of halogen group.

3)    If no of reactive group increases, binding also increases depending on dye structure.

4)    Reactive dye absorb up to 90%.

5)    Molecular weight of reactive group 69-211gm/ mole.

6)    Bond energy of halogen groups are as below:

 F (Fluorine)- 102-kcal/ gm

Cl (chlorine) – 74-kcal/ gm

Br (bromine) – 64-kcal/ gm

I (iodine) - 56-kcal/ gm

7)    If the molecular weight of reactive group increases, reactivity also increases.

8)    Reactivity of iodine is high but tits rate of hydrolysis is also high.

9)    Chlorine imparts medium reactivity, but it is cheap and hydrolysis rate is medium.

10) Reactivity of fluorine is the least and its rate hydrolysis is also less.

11) Reactivity of vinyl sulphone group increases with increasing temperature and pH.

12) Sulphone group has more solubility but it is not stable.

13) Generally low molecular weight dyes are of hot brand.

14)  Less affinity dyes are used for pad method.