Pigment Yellow 97
Color Index Pigment Yellow 97 is widely used as a yellow colorant, and is classified as an arylide yellow. It is distinguished by the presence of a sulfonylaminophenyl group, which renders the material particularly insoluble.
Properties
Pigment Yellow 97 exhibits extremely high light fastness and weather fastness. Its resistance to organic solvents and its recoatability are superior to those of other monoazo pigments. The presence of an N-phenylsulfonamide group improves migration fastness.Although the compound is often depicted as an azo compound, X-ray crystallography shows that the hydrazone form is favored as a result of azo-hydrazo-tautomerism.
Production
It is derived from two fairly complicated precursors. The acetoacetanilide component is made from 2,5-dimethoxy-4-chloroaniline. The azo component is made from a dimethoxyaniline with the sulfonylaminophenyl substituent. The compound is obtained via acetoacetylation of o-tolidine using diketene. The resulting bisacetoacetylated compound is coupled with two equiv of the diazonium salt obtained from 2,4-dichloroaniline.Arylide yellow pigments are obtained by acetoacetylation of an aromatic amine with diketene, followed by reaction with a diazo component in an azo coupling to form the pigment. Pigment Yellow 97 is produced by diazotization of 4-amino-2,5-dimethoxy-N-phenylbenzenesulfonamide and subsequent coupling of the diazo component with 4-chloro-2,5-dimethoxyacetoacetanilid. The coupling component is obtained by reaction of diketene with 2,5-dimethoxy-4-chloroaniline.