Andrew D. Towns

Developments in azo disperse dyes derived from heterocyclic diazo components

Abstract Advances over the last decade concerning the synthesis, properties and application of azo disperse dyes prepared from diazo components containing aromatic heterocycles are discussed. ©

Dyes derived from aminothiophenes. Part 4: Synthesis of some nitro-substituted thiophene-based azo disperse dyes

Abstract A series of thienylazo dyes has been prepared from nitro-substituted 2- and 3-aminothiophenes; colorants from the former were reddish-blue to green, whereas those from the latter were yellow to orange. The 2-aminothiophenes were obtained either by the amination of an activated chlorothiophene or by the functionalisation of thiophenes synthesised using the Gewald reaction. The thienyl-3-azo dyes were prepared from derivatised 3-amino-2-methoxycarbonylthiophenes. The 13 C NMR chemical shifts of a nitrothienyl-2-azo dye are reported together with those of a 5-nitrothiazolyl-2-azo analogue.

Dyes derived from aminothiophenes. Part 7: Synthesis and properties of some benzo[b]thiophene-based azo disperse dyes

Abstract A series of monoazo dyes has been synthesised from 2- and 3-amino-benzo[b]thiophene diazo components. The spectroscopic properties of the dyes were compared with literature data and theoretical expectations. Dispersions of the dyes were applied to hydrophobic fibres; the colorimetric and fastness properties of the resultant dyeings were evaluated.

A comparison of the properties of some 2-aminothiophene-derived disperse dyes

Abstract In the course of an investigation into the properties of monoazo disperse dyes synthesised from aminothiophene diazo components, significant discrepancies were observed between the spectroscopic and fastness data of some thienyl-2-azo dyes compared to that previously reported for closely related analogues. Considerable differences in λ max and e max values were noted; in some cases, light fastness ratings were at variance with previously disclosed figures.

Dyes derived from aminothiophenes. Part 1: Synthesis of some heterocyclic disperse dyes using the gewald reaction

Abstract A series of red to violet thienyl-2-azo disperse dyes has been derived from aminothiophenes synthesised directly by using the Gewald reaction. A variety of diazotisation conditions had to be employed owing to the differing basicities, hydrophobicities and stabilities of each thiophenamine. 13 C NMR data for certain derivatives are reported.

Dyes derived from aminothiophenes—Part 3. Application of some disperse dyes derived from 2-aminothiophenes to hydrophobic fibres

A series of thienyl-2-azo dyes has been milled and the dispersions applied to polyester, nylon and cellulose diacetate by conventional exhaustion dyeing techniques. The colour properties of the dyeings were examined and related to the molecular structure of the colorants. Generally, of the three substrates, polyester was found to be coloured most effectively; the nylon and acetate dyeings had lower colour yields. Although the dyeings were not of standard depth, correlations between dye structure and wash, perspiration and sublimation fastness were identified. Photostability was observed to improve as electron-withdrawing groups were attached to the thiophene ring.

Dyes derived from aminothiophenes. Part 6: Application of some nitro-substituted thiophene-based azo disperse dyes to hydrophobic fibres

Abstract Monoazo disperse dyes prepared from 2- and 3-aminonitrothiophenes were applied to three dydrophobic fibre types, furnishing reddish-blue to green and yellow to orange dyeings, respectively. Colour yields varied greatly: the dyes exhibited marked differences in build-up on polyester as a result of only small alterations in molecular structure, while the strengths of the nylon and diacetate dyeings were generally unsatisfactory. On the whole, levels of fastness on polyester were good; trends in wet and sublimation fastness were identified. The light-fastness ratings of the thienyl-2-azo dyes on polyester and diacetate were high and superior to those of the thienyl-3-azo analogues; however, on nylon, both dye types had poor photostability.

Dyes derived from aminothiophenes. Part 5: Spectral properties of some nitro-substituted thiophene-based azo disperse dyes

The spectroscopic properties of a series of nitro-substituted thienyl-2- and thienyl-3-azo dyes in neutral and acidic solution were examined. In agreement with resonance theory and PPP-MO calculations, nitrothienyl-2-azo derivatives were found to be more bathochromic than analogues lacking nitro groups. Absorption intensities, half-band widths and positive solvatochromic shifts were also greater; additionally, the nitrothienyl-2-azo dyes exhibited negative halochromism. The nitrothienyl-3-azo dyes were hypso- and hypochromic relative to their thienyl-2-azo isomers. The spectra and halochromism of the 2,4-disubstituted dyes indicated the presence of steric hindrance.

Properties of some novel monoazo disperse dyes derived from ester-substituted tetrahydroquinoline and indoline coupling components

Abstract Two series of dyes have been prepared by coupling conventional carbocyclic and heterocyclic diazo components to N - β -methoxycarbonylethyl-1,2,3,4-tetrahydroquinoline and N - β -methoxycarbonylethylindoline. The spectroscopic characteristics of the dyes were consistent with theoretical expectations as well as literature data for analogous structures derived from tetrahydroquinoline and indoline couplers. No clear-cut structure–light fastness relationships were identified within either series, although a general correlation between ratings for these and previously-reported sets of related dyes was observed. Since alkoxycarbonylalkyl functions have been exploited as a means of conferring alkali-clearability on commercial colorants, several members of the synthesised range of dyes were examined for signs of this behaviour; comparison with isomeric N -acetoxyethyl analogues indicated that the presence of a single N - β -methoxycarbonylethyl residue was not sufficient to bring about a significant effect.

Dyes derived from aminothiophenes—Part 2. Spectroscepic properties of some disperse dyes derived from 2-aminothiophenes

Abstract The colour properties of a series of red to violet thienyl-2-azo disperse dyes in solution have been investigated. As expected, the attachment of increasingly electron-withdrawing groups to the thiophene ring resulted in bathochromic and hyperchromic shifts. The shifts in absorption maxima were predicted quantitatively by PPP-MO calculations with reasonable accuracy. The solvatochromism and halochromic behaviour of the dyes were also examined.