Direct Condensation Dyes

Condensation dyes from 4-nitrotoluene-2-sulfonic acid are the most important of the stilbene dyes. Direct YeUow 11 (Cl 40000), discovered in 1883 and commonly known as Sun YeUow [1325-37-7] is widely used in the paper industry (2,4). 

More conveniently, compound (13) was directly condensed with barbituric acid (14) in acetic acid (28) or in the presence of an acid catalyst in an organic solvent (29). The same a2o dye intermediate (13) and alloxantin give riboflavin in the presence of palladium on charcoal in alcohoHc hydrochloric acid under nitrogen. This reaction may involve the reduction of the a2o group to the (9-phenylenediamine by the alloxantin, which is dehydrogenated to alloxan (see Urea) (30). 

As in the case of the metal-free direct dyes, a large diversity of structures is encountered here, too, there are direct dyes with pyrazolones, substituted 4,4 -diphenylamines, or the 1,3,5-triazine ring, urea and stilbene derivatives, and condensation dyes. 

Isatin is used as such in the preparation of many valuable vat dyes. Still more important are the vat dyes prepiuea directly from a-isatinanilide by condensation with -hydroxythionaphthenes. As first observed by G. Engi, isatin and a-isatin-anilide lead to different dyes on condensation. In the case of isatin itself, the p group is reactive in the condensation reaction, while with a-isatinanilide, aniline is split out and o condensed dyes are formed. These a condensation products are much.more valuable as dyes than the isomeric p compounds. 

Azo-stilbene dyes formed by condensation of 4,4 -dinitro-2,2 -stilbenedisulfonic acid or 4,4 -dinitro-2,2 -dibenzyldisulfonic acid (1) with aminoazo compounds. Direct Orange 34 (Cl 40215) [32651-66-4] (5) is a representative ... 

Azo-stilbene dyes formed by diazotization of a condensation product containing primary amino groups and coupling with azo dye coupling components, eg. Direct Brown 29 (Cl 40505) (6) ... 

Direct Orange 15 (Cl 40003) [1325-35-5] (13), which is made by reducing the alkaline condensation product equivalent to Direct YeUow 11 with sulfide or formaldehyde, is an important paper dye used in dyeing brown paper for bags. 

In the ketone method, the central carbon atom is derived from phosgene (qv). A diarylketone is prepared from phosgene and a tertiary arylamine and then condenses with another mole of a tertiary arylamine (same or different) in the presence of phosphoms oxychloride or zinc chloride. The dye is produced directly without an oxidation step. Thus, ethyl violet [2390-59-2] Cl Basic Violet 4 (15), is prepared from 4,4 -bis(diethylamino)benzophenone with diethylaruline in the presence of phosphoms oxychloride. This reaction is very useful for the preparation of unsymmetrical dyes. Condensation of 4,4 -bis(dimethylamino)benzophenone [90-94-8] (Michler s ketone) with AJ-phenjl-l-naphthylamine gives the Victoria Blue B [2580-56-5] Cl Basic Blue 26, which is used for coloring paper and producing ballpoint pen pastes and inks. 

Three important direct yeUows of revealed chemical composition belong to the stUbene class. Direct YeUow 11 (24) was mentioned earUer in the discussion of the condensation of nitro compounds. Another stUbene dye. Direct YeUow 4 (63), an old dyestuff discovered in 1886, is produced by coupling bisdiazotized 4,4 -diainino-2,2 -stilbenedisulfonic acid to two moles of phenol. 

Miscellaneous Dyes. Other classes of dyes that stiU have some importance are the stilbene dyes and the forma2an dyes. Stilbene ( es are in most cases mixtures of dyes of indeterminate constitution that are formed from the condensation of sulfonated nitroaromatic compounds ia aqueous caustic alkah either alone or with other aromatic compounds, typically arylarnines (5). The sulfonated nitrostilbene [128-42-7] (79) is the most important nitroaromatic, and the aminoa2oben2enes are the most important arylarnines. Cl Direct Orange 34 [2222-37-6] (Cl 40215-40220), the condensation product(s) of (79) and the aminoa2oben2ene [104-23-4] (80), is a typical stilbene dye. 

A large number of 1,2,4-triazines that are condensed with one or more heterocycles are well known and a wide variety of synthetic methods for their preparations are available. Compounds containing the 1,2,4-triazine moiety are in use as pharmaceuticals, dyes, pesticides, herbicides, etc., and a great number of reports have been directed to the synthesis of the title heterocycles having potentially useful biological properties. 

The earliest polymeric cationic aftertreatments stemmed from the development of crease-resist finishes for cellulosic fibres. One such, promoted specifically for its colour fastness improvements when applied as an aftertreatment to direct dyeings, was a condensation product of formaldehyde with dicyandiamide (Scheme 10.82). Many similar compounds followed, such as condensation products of formaldehyde with melamine (10.212), polyethylene imine) with cyanuric chloride (10.213) and alkyl chlorides with polyethylene imine) (10.214 R = alkyl). 

DAS (11.7) is synthesised from 4-nitrotoluene-2-sulphonic acid (11.6) by the route outlined in Scheme 11.1. An important factor in the preparation of DAST brighteners in the purity necessary for good performance is the purity of the DAS used as starting material. At one time DAS made in this way contained significant amounts of yellow azoxy compounds similar to 11.8, which formed the main components of the obsolescent dye Sun Yellow (Cl Direct Yellow 11) made by the partial reduction and self-condensation of intermediate 11.6. Today the major manufacturers supply DAS essentially free from these undesirable impurities [37]. 

Stilbene dyes are mixtures of indeterminate constitution resembling polyazo direct dyes in their application properties. They result from the alkaline self-condensation of 4-nitrotoluene-2-sulphonic acid (1.5) or its initial condensation product (1.6 X = N02),... 

Triphenodioxazine compounds have been used to make brilliant blue direct and reactive dyes for cellulosic fibres, but only one pigment in this chemical class, Cl Pigment Violet 23 (2.43), is widely used. It is prepared by condensing 3-amino-9-ethylcarbazole with chloranil in trichlorobenzene [29]. As with many other pigments, manufacturers offer it in many physical forms adapted to the intended end-use. 

The dioxazine ring system is the source of some valuable violet pigments, such as Cl Pigment Violet 23 (6.211). This colorant is obtained by condensing 3-amino-9 ethylcarbazole with chloranil. Sulphonation of the pigment gives the dye Cl Direct Blue 108. Triphenodioxazines have recently been the source of some blue reactive dyes [241-Examples are known of symmetrical bifunctional structures (6.212 NHRNH = alkylenediamine, Z = haloheterocyclic system) and unsymmetrical monofunctional types such as 6.213 [37]. 

Selecting a sulphonated dye molecule containing an amino group as the nucleophile leads directly to a dichlorotriazine dye. In certain cases a suitable intermediate may be condensed with cyanuric chloride and then the chromogenic grouping is synthesised from this reaction product. Both of these routes are illustrated in a simple way for Cl Reactive Red 1 (7.1) in Scheme 7.7. In these dyes the electronic effects responsible for the lability of the chloro substituents are muted by feedback of electrons from the electron-donating imino bridging... 

Derived from tribenzodioxazine (79), coloured compounds of this type have been known since 1928 and have been used as reddish-blue direct dyes for cotton. An important violet, Carbazole Dioxazine Violet (80), was prepared by condensation of 3-amino-A-ethylcar-bazole with chloranil followed by cyclization of the intermediate diimine and pigmentary conditioning (56GEP946560). A second useful synthesis involves condensation of an o-alkoxyarylamine with chloranil followed by cyclization (65C242). 

Precursors for the grafting of the dyes can be anchored by different ways. In one route they are added to the structure directing surfactant and are encapsulated during the condensation process of the MCM-41 material.6 In an alternative route a preformed MCM-41 is modified by silylation.7 This paper reports an anchoring via the latter route. 

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