Phenylene Homologs of Benzidine: Mutagenicity and Use in Organic Dyes and Pigments Synthesis

Abstract

This dissertation is concerned with the synthesis and evaluation of direct dyes and pigments in which diamines 4,4'-diamino-para-terphenyl (DATP) and 4,4'-diamino-para-quaterphenyl (DAQP) were employed as potential alternatives to benzidine. DATP was synthesized by direct nitration of para-terphenyl and reduction of the resultant dinitro compound using hydrazine and Pd catalyst. DAQP was synthesized from biphenyl firstly by nitration and iodization, the Cu-induced coupling of the resultant 4-iodo,4'-nitrobiphenyl afforded 4,4'-dinitro- para-quaterphenyl, which was reduced to the target diamine using SnCl2/HCl.

Organic dyes were prepared by coupling DATP or DAQP to the widely used dye intermediates: naphthionic acid, J-acid, H-acid, chromotropic acid and Chicago acid. The purity of all dyes was assessed by TLC and electrospray mass spectrometry (ESMS) was used to confirm dye structures.

Organic pigments were prepared by coupling or condensing DATP or DAQP with intermediates such as 2-mercapto-4,6-dihydroxypyrimidine, acetoacetanilide, 1-phenyl-3-methyl-5-pyrazolone, 5-acetoacetyl-aminobenzimidazolone and 4-[(2,5-dichlorophenyl)azo]-3-hydroxy-2-naphthoyl chloride.

The standard Ames test and Prival modification were used to assess mutagenicity. The results showed that DATP was mutagenic, while DAQP was nonmutagenic. Most of the dyes based on DATP and DAQP were nonmutagenic in the Ames test. .All pigments based on DATP and DAQP were nonmutagenic, which may be accounted for by the extremely low solubility of the pigments in the test media.

The results of this study indicate that both diamines can be used to make disazo and azomethine organic colorants; however due to the mutagenicity of DATP, only DATQ could be accepted as a synthetic intermediate, despite the lack of mutagenicity in organic pigments derived from the former diamine. Further, the high melting and decomposition temperatures associated with organic pigments derived from DAQP suggest that they are suitable for applications requiring high performance pigments, such as the coloration of fibers and plastics during melt extrusion.