Chemical structure of Reactive Dyes

Chemical structure of Reactive Dyes

Introduction:

Compare to direct dyes or acid dyes, reactive dyes are different in their chemical structure,reaction and thier fastness performance. 

the above figure shows the example of chemical structure of reactive dyes.Red colour reactive dye structure. The structure is formed by the arrangements of benzene rings,chemical groups with bindings.For readers information,chemical structures of dyes are read in many ways.Some authors read in R-B-X form and some in D-B-G-S form. Here we consider as "General structure of reactive dyes in C-B-R form".

Study of structure in C-B-R  form. 

C indicates first letter of the word chromogen or chromophore, is a colour producing part or substrate of reactive dyes.The cause to produce colours yellow ,red, blue ,etc,.whatever that colour making part is called chromogen or chromophore.In the above structure Sodium sulphide NaSo3 is the colour making part.

B indicates first letter of the word bridging for bridging group.Bridging group makes link between colour part and reactive group.Bridging group here is -NH.

R indicates the first letter of the reactive group.Another group formed with Cl. That is chloride particle. This is the reactive group.This will react with the polymer chain of the textile fibres.

So the structure contain Sodium sulphide NaSo3 polymer chain, -OH group, -NH group and Cl group.Totally making red colour reactive dye.

In this reactive red colour,sodium sulphide is there,-NH is there and Cl is there.But in other case,Bromine Br will be there in place of Cl and ethyl or methyl or oxide will be there in place of -NH bridging group.

And one more point in this reactive dye is most of the cases,the colour making part may change.This may be an Azo or Anthraquinon,phthalocyanon or metal complex. Colours are made by these chromogen or chromophore groups.But study saying that most of the dyes are made of Azo groups.

Colour group,bridging group and reactive group. These three parts are there in any reactive chemical structure. But chemicals will be changed.

Note: This article will be updated as and when required.

Source:

1.Ref: Chemistry of Dyes and Principles of Dyeing by V A Shenai.

2.Educational qualification and industrial experience of the author/blogger.