Brighteners

Unsubstituted 2-aminothiazole was proposed as a food seasoning (1020). This product w as found the most effective brightener for a... 

Optical amplifiers Optical bleaches Optical brighteners... 

Mordant Red 27 [6539-224] 45180 Brightener 74 Chromoxane 4.5 4.5 American Hoechst Corp. 

Phenylstilben-4-yl)benzoxazoles are prepared by means of the anil synthesis from 2-(4-methylphenyl)benzoxazoles and 4-biphenylcarboxaldehyde anil, and used for brightening polyester fibers (24,25). An example is (3) [16143-18-3]. 

Bis(azol-2-5l)stilbenes (2(i]ll such as (4) have been prepared. 4,4 -Dihydrazinostilbene-2,2 -disulfonic acid, obtained from the diamino compound, on treatment with 2 moles of oximinoacetophenone and subsequent ring closure, leads to the formation of (4) [23743-28 ]. Such compounds are used chiefly as washing powder additives for the brightening of cotton fabrics, and exhibit excellent light- and hypochlorite-stabiUty. 

PyraZolines. l,3-Diphenyl-2-pyia2olines (7) (Table 2) aie obtainable from appiopiiately substituted phenyUiydiazines by the Knoii reaction with either P-chloro- or P-dimethylaminopropiophenones (30,31). They are employed for brightening synthetic fibers such as polyamides, cellulose acetates, and polyacrylonitriles. 

Bis(benZoxaZol-2-yl) Derivatives. Bis(benzoxazol-2-yl) derivatives (8) (Table 3) aie prepared in most cases by treatment of dicaiboxyhc acid derivatives of the central nucleus, eg, stilbene-4,4Cdicarboxyhc acid, naphthalene-l,4-dicarboxyhc acid, thiophene-2,5-dicarboxyhc acid, etc, with 2 moles of an appropriately substituted o-aminophenol, followed by a ring-closure reaction. These compounds are suitable for the brightening of plastics and synthetic fibers. 

Goumanns. By treatment of flax with escuUn, a glucoside of esculetin [305-01-1] (10), a brightening effect is achieved however, this effect is not fast to washing and light. The use of P-methylumbeUiferone [90-33-5] (11) and similar compounds as brighteners for textiles and soap has been patented. 

As improvements over P-methylumbeUiferone (55—57), 4-methyl-7-amino-coumarin [26093-31-2] (12a) and 7-dimethylamino-4-methylcoumarin [87-014] (12b) (58—61) were proposed. These compounds are used for brightening wool and nylon either in soap powders or detergents, or as salts under acid dyeing conditions. They are obtained by the Pechmaim synthesis from appropriately substituted phenols and P-ketocarboxyflc acid esters or nitriles in the presence of Lewis acid catalysts (see Coumarin). 

A further development in the coumarin series is the use of derivatives of 3-phenyl-7-aminocoumarin ((13) where R, R = Cl or substituted amines) as building blocks for a series of light-stable brighteners for various plastics and synthetic fibers, and, as the quatemi2ed compounds, for brightening polyacrylonitrile (62). 

The pyrene derivative (17) [3271-22-5] is obtainable by the Friedel-Crafts reaction of pyrene with 2,4-dimethoxy-6-chloro-j -triazine, and is used for brightening polyester fibers (75). 

Oiiaternized pyridotriazoles can be used for brightening acryflc fibers (76). 

Both -hydroxybenzaldehyde and its methyl ether, -methoxybenzaldehyde [123-11-5] (p-anisaldehyde) have found extensive use in electroplating. The most widespread appHcation has been in alkaline bright zinc plating, both in non-cyanide (77) and in cyanide-containing (78) baths. The aldehydes act as both brightening and leveling agents. 

Material Protection. The graft copolymers of ethylene sulfide on polyethyleneimine can be used as an antifouHng anticorrosion substrate for iron (439). PEIs or their derivatives are also used in electrolysis baths as brighteners in the electrochemical deposition of metals (440,441). 

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