Numerous literature reports are available in recent years to
supplement this paradigm shift in azo dye utilization. In order
to create novelty and to increase the fixation of reactive dyes
on fibers bis anilines were used as bridging groups. Thus
substituted anilines were treated with dilute solution of formaldehyde,
at low temperature in order to avoid polymerization.
Conc. HCl was used to protonate the NH2 group in differently
substituted anilines, to peter out the nucleophilicity of the NH2
group. Short duration of time about 2 h was required for the
completion of reaction. Neutralization of reaction mixture
was achieved with 10% NaOH solution which resulted in the
separation of product, by snatching the proton and making
the product insoluble in aqueous medium. The synthetic route
to novel bis anilines (1a–j) has been sketched in Scheme 1.