Diaminostilbene

Many chemical compounds have been described in the Hterature as fluorescent, and since the 1950s intensive research has yielded many fluorescent compounds that provide a suitable whitening effect however, only a small number of these compounds have found practical uses. Collectively these materials are aromatic or heterocycHc compounds many of them contain condensed ring systems. An important feature of these compounds is the presence of an unintermpted chain of conjugated double bonds, the number of which is dependent on substituents as well as the planarity of the fluorescent part of the molecule. Almost all of these compounds ate derivatives of stilbene [588-59-0] or 4,4 -diaminostilbene biphenyl 5-membeted heterocycles such as triazoles, oxazoles, imidazoles, etc or 6-membeted heterocycles, eg, coumarins, naphthaUmide, t-triazine, etc. 

Approximately 75% of fluorescent brighteners belong to the stilbene class. These are almost invariably derived from 4,4, diaminostilbene 2,2, disulphonic acid (1.6 X = NH2), often condensed with cyanuric chloride to take advantage of the further contribution of the s-triazine rings to substantivity for cellulose. 

It is possible to tailor dyes, by use of the stepwise reactivity of the chlorine atoms in cyanuric chloride (B-59MI11200), to a variety of applications. For example, in structure (16), two molecules of cyanuric chloride may be reacted with one molecule of a suitable diamine, such as 4,4 -diaminostilbene-2,2 -disulfonic acid, at 0-5 °C and then the subsequent bis-dichlorotriazinyl product condensed with two molecules of an azo dye with a primary amino group at 35-40 °C. The resultant dyes are applied very efficiently to cellulosic fibres at 85-90 °C with very little dye remaining in the dyebath. The same molecule may also be prepared by condensation of the dye with cyanuric chloride at 0-5 °C and then with the diamine at higher temperature. Dyes more suitable for printing application may be prepared by condensation of a dye-amino group with cyanuric chloride followed by a diamine and then a further molecule of cyanuric chloride. The various applications are manifested in the various ranges of ICI s Procion dyes. 

Bis-substitution of stilbene produces stronger fluorescence and the bis-triazine derivatives of diaminostilbenes have proved to be the most successful brighteners for cellulosics, in particular, and polyamides (60MI11200). The variety of substitution permutations in (90) is almost endless and many primary and secondary homocyclic and heterocyclic amines, thiols and phenols have been used. Synthesis of such compounds is straightforward and utilizes the convenient selectivity to substitution of cyanuric chloride. 4,4 -Diaminostilbene-2,2 -disulfonic acid condenses readily at 0-5 °C with cyanuric chloride, under slightly acidic conditions. In this case cyanuric chloride behaves as a monofunctional acid chloride and, although some by-products are unavoidable, two molecules of cyanuric chloride condense... 

C. I. Direct Yellow 12, 24895 [2870-32-8] 4,4 -Diaminostilbene-2,2 -disulfonic acid is bis-diazotized with an aqueous solution of sodium nitrite at 5°C. Next, phenol is dissolved in water, and sodium hydroxide solution and soda are added. To this solution is added the above bis-diazotized solution. Then, more 30 % sodium hydroxide solution is added. On the following morning, the solution is heated to 70 °C, and after addition of 30 % hydrochloric acid, the dye is salted out with rock salt. The damp press cake, ethanol, soda, 30 % sodium hydroxide solution, and ethyl chloride are kept in a closed stirrer vessel for 24 h at 100 °C (5 - 5.5 bar). The mixture is then cooled to 70 °C and transferred at its own pressure to a distilling vessel, from which the ethanol is distilled. After being cooled to 80 ° C, the mixture is suction filtered and dried at 100 °C. 

Walther obtained the first direct dyes by self-condensation of 4-nitrotoluene-2-sulfonic acid. So-called Sun Yellow is a mixture of different components, depending on the concentration of sodium hydroxide, the temperature, and the duration of the reaction. Oxidation of the intermediate dye and subsequent reduction with iron and hydrochloric acid gives 4,4 diaminostilbene-2,2 -disulfonic acid, which is used for fluorescent whitening agents and azo dyes. The shades are mostly yellow to red. The structure of Direct Yellow 11, 40000 [65150-80-3] (13 is one of the main components) probably contains a mixture of stilbene, azo, and/or azoxy groups. 

With the l,3,5-triazin-2-yl derivatives of 4,4 -diaminostilbene-2,2 -disulfonic acid proposed by B. Wendt in 1940 [25], optical brighteners came into full-scale industrial use. In 1941, 4,4 -bis (4-anilino-6-hydroxy-l,3,5-triazin-2-yl)aminoJstil-bene-2,2 -disulfonic acid disodium salt was introduced commercially under the trade name Blankophor B (3) [1264-32-0],... 

Triazinyl derivatives of 4,4 -diaminostilbene-2,2 -disulfonic acid have been available since 1941 and remain the most important class of optical brighteners in terms of quantity. Some 75 derivatives have been put on the market [1], In the textile industry, they find use in brightening cotton, regenerated cellulosic fibers, and polyamides. They can also be included in detergent formulations and used to brighten paper, either in the pulp or in the coating. 

The starting compound for all triazinylaminostilbenes is 4,4 -dinitrostilbene-2,2 -disulfonic acid [128-42-7], which is obtained by oxidizing 4-nitrotoluene-2-sulfonic acid with aqueous sodium hypochlorite in the presence of sodium hydroxide or, more recently, by atmospheric oxidation in an aqueous ammoniacal medium [39], The Bechamps reduction using iron filings etched with hydrochloric acid yields 4,4 -diaminostilbene-2,2 -disulfonic acid [81-11-8] (DAS). 

Polyamides. Batch brightening usually takes place in combination with reductive bleaching (dithionite). Continuous processes (padding) are followed by steam, heat, or acid treatment (acid shock) [129], Anionic FWAs are absorbed similarly to acid dyes, or insoluble dispersion brighteners are suitable. Examples of products listed in order of increasing fastness are diaminostilbenes (14 and 19) pyra-zolines (50 and 54) distyrylbiphenyls (10) and bis(triazolyl)stilbenes (32). 

Sorensen M, Frimmel FH. Photochemical degradation of hydrophilic xenobiotics in the UV/H202 process influence of nitrate on the degradation rate of EDTA, 2-amino-1-naphthalenesulfonate, diphenyl-4-sulfonate and 4,4 -diaminostilbene-2,2 -disulfonate. Water Res 1997 31 2885-2891. 

They obtained the following results p-Dinitrostilbene, reduced in alkaline solution, gives p-azoxystilbene in hydrochloric-acid solution with addition of stannous chloride (method of C. F. Boehringer Sohne), p-diaminostilbene. 

Fig. 13.93. Tetrazotization of a di-n-propoxybenzidine (top) and a diaminostilbene disulfonic acid (bottom).

Diaminostilbene-2,2 -disulfonate KrCl + H2O2 hv n.s. 0.01 mmol HPLC Sorensen and Frimmel (1997)... 

Sorensen M, Frimmel F (1997) Photochemical Degradation of Hydrophilic Xenobiotics in the UV/H2O2 Process Influence of Nitrate on the Degradation Rate of EDTA, 2-Amino-l-naphthalenesulfonate, Diphenyl-4-sulfonate and 4,4 -Diaminostilbene-2,2 -disulfonate, Wat. Res. 31 2885-2891. 

Diammonium phosphate 4, 6-Diamidino-2-phenyUndole dihydrochloride 4,4 -Diaminostilbene-2,2 -disulfonic acid N,iV-Diethylaminosulfur trifluoride iV,iV-Dimethylaminosulfur trifluoride Diethylaluminium 2,2,6,6-tetramethylpiperidide... 

Certain unsaturated amino compounds like the cis- and trans-p,p r diaminostilbenes and -diaminotolane are prepared by selective hydrogenation of the corresponding dinitro compounds using Raney nickel catalyst (60-8S>%). The reduction has also been accomplished with hydrazine hydrate in the presence of alkali. ... 

Aromatic nitro compounds are reduced to amines by hydrazine in hot diethylene glycol with or without base. In the presence of alkali p-nitrotoluene affords the dimeric p,p -diaminostilbene, while p-to-luidine is obtained without the base. ... 

---