Bleach peracids

Peracids can be introduced into the bleaching system by two methods. They can be manufactured separately and deHvered to the bleaching bath with the other components or as a separate product. Peracids can also be formed in utilizing the perhydrolysis reaction shown in equation 17. 

Peracid Precursor Systems. Compounds that can form peracids by perhydrolysis are almost exclusively amide, imides, esters, or anhydrides (85). Two compounds were commercially used for laundry bleaching as of 1990. Tetraacetylethylenediarnine (TAED) [10543-57-4] is utilized in over 50% of Western European detergents (5). The perhydrolysis reaction of this compound is shown in equation 19. T A ED generates two moles of peracid and one mole of diacetylethylenediamine per mole of imide (93). 

The NOBS system undergoes an additional reaction that forms a diacyl peroxide as a result of the nucleophilic attack of the peracid anion on the NOBS precursor as shown in equation 21. This undesirable side reaction can be minimized by the use of an excess molar quantity of hydrogen peroxide (91,96) or by the use of shorter dialkyl chain acid derivatives. However, the use of these acid derivatives also appears to result in less efficient bleaching. The dependence of the acid group on the side product formation is apparentiy the result of the proximity of the newly formed peracid to unreacted NOBS in the micellar environment (91). A variety of other peracid precursor stmctures can be found (97—118). 

Two sohd organic peracids have been utilized ia textile bleaching products. Diperoxydodecanedioic acid, (16), [66280-55-5] a hydrotropic peracid, and the magnesium salt [78948-87-5] of monoperoxyphthaUc acid, (17), [2311-91-3] a hydrophilic peracid, were contained in bleaching products for a short period of time (142). 

In traditional peroxide bleaching, hydrogen peroxide is activated by alkali. Acids, both inorganic and organic, can also be used to activate peroxide by the formation of a peracid. Peracids can be effective oxidative bleaching agents and, at least potentially, offer an alternative to the environmentally sensitive chlorine bleaches. Although known for quite... 

In the context of peracid bleaching it is worthwhile recalling the reaction outlined in Scheme 10.30, in which peracetic acid is produced in situ by the action of the activator tetra-acetylethylenediamine (10.86) on hydrogen peroxide [244]. 

Peracids -acetic acid as by-product of [ACETIC ACID AND DERIVATIVES - ACETIC ACID] (Vol 1) -as disinfectant piSINFECTANTS AND ANTISEPTICS] (Vol 8) -10 hHLT [PEROXIDES AND PEROXIDE COMPOUNDS - ORGANIC PEROXIDES] (Vol 18) -for propylene oxide mfg [PROPYLENE OXIDE] (Vol 20) -as bleach [BLEACHING AGENTS - SURVEY] (Vol 4) -reactions of [IMINES, CYCLIC] (Vol 14)... 

Several oxidants (Fig. 1) are used as the oxygen source. Examples are bleach (NaOCl), hydrogen peroxide (H202), organic peroxides like dimethyldioxyrane (DMD) or ferf-butyl hydroperoxide (TBHP), peracids like m-chloroperbenzoic acid (mCPBA) or potassium monoperoxysulfate (KHSO5). 

The addition of either PhIO, C6F5IO, or excess peracid to an anaerobic solution of 19 at low temperatures in the absence of substrate generates a transient species with a dark orange-red color (44). This color bleaches rapidly upon precipitation of the /it-oxo dimer or the addition of substrate. This species has a solution half-life of 1.5 h at —80 °C. Characterization of the intermediate is not yet reported. 

The peroxygen bleaches, typically perborate or percarbonate salts, produce peroxide in aqueous solutions. The effectiveness of peroxide as an oxidizing agent at relatively low wash temperatures (120 to 140°F) is unfortunately minimal. Peracids (RC(O)OOH), which can be generated by the activation of carboxylic acids by peroxide or can be added directly, have not found use in LADD compositions in spite of their relatively high oxidation potentials because of their instability in aqueous solution. 

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