In a reactive dye a chromophore contains a substituent that is actived and allowed to directly react to the surface of the substrate.
Reactive dyes frst appeared commercially in 1956, after their invention in 1954 by Rattee and Stephens at the ICI Dyestuffs Division site in Blackley, Manchester, UK. They are used to dye cellulosic fibres. The dyes contain a reactive group, either a halo heterocycle or an activated double bond, that, when applied to a fibre in a weakly alkaline dye bath, forms a chemical bond with an hydroxyl group on the cellulosic fibre.
Reactive dyeing is now the most important method for the coloration of cellulsic fibres. Reactive dyes can also be used to dye wool and nylon, in the latter case they are applied under weakly acidic conditions.
Other reactive dyes: