Azines, Oxazines and Thiazines

These chromophores have declined significantly in importance as textile dyes bnt have remained of interest becanse of their fluorescent behaviour, as discussed in Chapter 3, section 3.5.1.5. One exception is the triphenodioxazine ring system, which is used to produce valuable blue dyes in the Direct (2.19) and Reactive dye classes (2.20) as well as pigments (see section 2.4.1.7). The dyes from this chromogen have a very high molar absorption coefficient (ca. 80 000) versus typical anthraquinone dyes (ca. 15 000) and have therefore replaced some of the dyes from this latter chromogen in the reactive dyeing of cotton.  

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Azine, oxazine, and thiazine dyes were among the earliest of synthetic dyes. The names are derived from the 6-member heterocycHc ring system present in... 

Azine, oxazine, and thiazine dyes were historically more important than they are at present. However, at least one example of each, introduced more than 100 years ago, is still offered commercially today (1,2). Azo and anthraquinone dyes have largely displaced them in commercial appHcation. Azo dyes (qv) offer better fastness and broader shade ranges at more economical prices. 

Azine, oxazine, and thiazine dyes were among the eadiest of synthetic dyes. The names are derived from the 6-member heterocyclic ring system present in all dyes of these classes 1,4-diazine [290-37-9] (1), 1,4-oxazine [290 17-1] (2), and 1,4-thiazine [290-57-3] (3). 

Williams, J. A. Antimalarial dyes revisited xanthenes, azines, oxazines, and thiazines. Antimicrob. Agents Chemother. 1995, 39,... 

Related to the xanthene dyes are the acridines, azines, oxazines, and thiazines. Acridine Yellow results from the fusion of toluene-2,4-diamine with glycerin and oxalic acid, followed by oxidation with ferric chloride. Basic Orange 15 (Phosphine) is a by-product of the manufacture of Basic Violet 14 (Fuchsine) and is an acridine dye. 

However, in many other series results have been obtained that are compatible with those from other methods and that gave the dipole-moment method an appearance of general reliability now known to be unjustified. Such compatible results include spiropiperidines (Section III,A,4), tropanes (Section III,B,4), 2-alkyltetrahydro-l,2-oxazines (Section III,C,2), perhydro-pyrido[l,2-c][l,3]oxazines (Section III,D,IX perhydropyrido[l,2-c][l,3]thi-azines (Section III,D,2), dialkylhexahydropyrimidines and perhydropyrido-[l,2-c]pyrimidines (Section III,D,3), 5-alkyldihydro-l,3,5-dithiazines (Section III,G,3), 3,5-dialkyltetrahydro-l,3,5-thiadiazines (Section III,G,4) and, in part, l,2,4,5-tetraalkylhexahydro-l,2,4,5-tetrazines (Section III,H,4) as well as piperidines, tetrahydro-l,3-oxazines, and tetrahydro-l,3-thiazines containing an N-H group. 

Oxazine, azine and thiazine dyes are named for the characteristic heterocyclic ring systems 1,4-oxazine, 1,4-diazine, and 1,4-thiazine. The dyes are generally cationic (basic) or acid dyes. They also can be reduced to colorless forms, then oxidized back to the dye, as in vat dyeing. The dyes also have been used to a limited extent in disperse and fiber reactive applications. They are used as titration indicators and may be applied to acrylic fibers and leather. 

The most important leather dyes identified by typical chemical nomenclature are azo, stilbene, triaiylmethane, quinoline, azine, oxazine, thiazine, sulfur, and phthalocyanine. 

Cationic dyes include the basic dyes and some of the mordant dyes that are designed to bind acidic sites on a substrate, such as fibers. Useful t5q>es of such dyes include the azo compounds, diphenylmethane compounds, triarylmethanes, xanthene compounds, acridine compounds, quinoline compounds, methine or polymethine compounds, thiazole compounds, indamine or in-dophenyl compounds, azine compounds, oxazine compounds, and thiazine compounds. 

Dye Classification Based on chemical structure or chromophore, 20-30 different groups of dyes can be discerned. Azo (monoazo, disazo, triazo, polyazo), anthraquinone, phtha-locyanine and triarylmethane dyes are quantitatively the most important groups. Other groups are diarylmethane, indigoid, azine, oxazine, thiazine, xanthene, nitro, nitroso, methine, thiazole, indamine, indophenol, lactone, aminoketone and hydroxyketone dyes and dyes of undetermined structure (stilbene and sulphur dyes). The vast array of commercial colourants is classified in terms of colour, structure and application method in the Colour Index (C.I.), which has been edited since 1924 (and revised every three months) by the Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. Each dye is given a C.I. generic name determined by... 

Basic dyes are triarylmethane, xanthene, azine, oxazine, thiazine and acridine derivatives. Azo and methine dyes are encountered particularly as colouring agents for polyacrylonitrile fibres. 

Dyes, azine used for azines, thiazines, and oxazines (AziNEDYEs). 

Reduction and reoxidation tests. Reduction with hydrosulphite B X is effected by boiling the fabric in this reagent for about two minutes. Azines, thiazines, oxazines, etc., and most of the azo-dyestuffs are completely reduced in about half a minute, but insoluble azo-dyestuffs require more prolonged boiling for their complete reduction. 

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