Synthesis, Structure Investigation and Dyeing Assessment of Novel Bisazo Disperse Dyes Derived from 3-(2'-Hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones

In an attempt to find a new class of bisazo disperse dyes with better dyeing properties, a series of novel bisazo dyestuffs based on 4-arylhydrazono-3-(2'-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones 3a-f were prepared by diazocoupling of p-nitrophenyl diazonium chloride with 4-arylhydrazono-3-(2'-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones 2a-f. Compounds 3a-f were subsequently reacted with acetic anhydride in the presence of p-toluenesulfonic acid afford the corresponding O-acetyl derivatives 4a-f. The latter products as well as spectral data indicated that compounds 3a-f exist predominantly in the azo-hydrazone tautomeric form (H) as the ZE-configuration. Additionally, two series of the synthesized dyes 3a-f and 4a-f were applied as disperse dyes for dyeing polyester fabrics and their fastness properties were evaluated. Also the position of color in CIELAB coordinates (L*, a*, b*, H*, C*) was assessed.