Peracids precursors

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). 

The pify of the leaving group and the hydrophobe chain length can dramatically affect the efficiency of the perhydrolysis reaction. Additionally, the stmcture of the acid portion of the precursor can affect the yield and sensitivity of the reaction to pH. The mono-4-hydroxybenzenesulfonic acid ester of a-decylsuccinic acid (13) undergoes extremely efficient perhydrolysis at much lower pHs than other peracid precursors, eg, decanoyloxybenzene sulfonate (14). This may be because of the neighboring group participation of the adjacent carboxylate as shown in Table 2 (115). 

The peracid—exotherm control agent mixtures can be granulated using a variety of techniques common in the industry, including agglomeration. As with peracid precursors, the surface area to volume ratio can impact the stabiUty of the peracid. Particles are thus made as large as possible to maintain stabihty (141). 

In contrast to sensitive preformed peracids, bleach activators are safe to handle and, in granulated form, reasonably storage-stable in alkaline detergent powders or tablets. Bleach activators are organic compounds having at least one reactive acyl group R-CO (peracid precursor group), which... 

Providiug delayed release of ingredients which degrade enzymes in the wash water. This approach has been used for peroxygen bleaches [70], accomplished by coating the peracid precursor with polyethylene glycol (MW 4000) and citric acid and the percarbonate with silicate. 

Attempts have also been made to reduce the odor associated with the peracid in the home laundry. Use of a precursor that generates the peracid of a fatty acid can result in an objectionable odor in the wash bath (106). This odor is exacerbated by the higher piC of the peracid versus its parent acid resulting in a greater proportion of the peracid in the unionized and therefore less water-soluble form. To mitigate this circumstance, functionalization of the fatty tail typically alpha to the carbonyl has been utilized (112). The modifications include alpha-chloro and alpha-methoxy substituents on the parent acid portion of the precursor ester. 

It has been proposed that oxygen adds to the excited keto group [- (112)]. The rearrangement of the resulting hydroxyhydroperoxy diradical (112) could then proceed by intramolecular hydrogen abstraction involving a six-membered cyclic transition state, followed by fission of the former C —CO bond to form the unsaturated peracid (113) as the precursor of the final product. Such a reaction sequence demands a hydrogen atom in the J -position sterically accessible to the intermediate hydroperoxy radical. 

Catalytic oxidation of ozonides over platinum appears to be accompanied by the same ester by-product disadvantage found in the thermal process. Chain degradation by other reactions is less serious, however, and transesterification does not occur. The method can therefore be used to prepare a half-ester of a dicarboxylic acid from an ester of a suitable unsaturated acid. If ozonide autoxidation occurs by the route, ozonide — aldehyde — peracid, with the latter acting as precursor of both acid and ester products (20-24), it is interesting to compare reaction rates observed in the present study with the rate of uptake of oxygen by... 

Diels-AUer reactions. This diene can serve as a precursor to the highly oxygenated cyclohexane derivative shikimic acid (3), as shown in Scheme 1. Oxidative desilylation of the Diels-Alder adduct 2 could not be effected with peracids, but was effected by cis-dihydroxylation (Upjohn procedure, 7, 256-257) followed by p-elimination of (CH3)3SiOH with TsOH. Introduction of the 4a,5P diol system was effected indirectly from the 4a,5a-epoxide in several steps, since direct hydrolysis of the epoxide resulted in a mixture of three triols.1... 

Oxaspiropentanes have been synthesized by the epoxidation of methylenecyclo-propanes with peracetic49), peroxybenzimidic 50), with p-nitroperbenzoic46) and m-chloroperbenzoic acid51). The parent oxaspiropentane 95, a convenient precursor of cyclobutanone 46was obtained from the peracid oxidation of a methylene chloride solution of methylenecyclopropane 94, Eq. (27)46,51). 

Purines react slowly with peracids, such as perbenzoic acid (within a week), to yield the 1-oxide. An early report of the synthesis of a purine A -oxide by direct oxidation was the preparation of adenine 1-oxide (1) from the treatment of adenine with acetic acid/hydrogen peroxide. Related purine 1-oxides can be obtained from adenine 1-oxide by deamination. As most purine 7- and 9-oxides are not accessible by direct oxidation, the cyclization of the corresponding pyrimidine or imidazole precursors was undertaken. A review on heterocyclic A-oxides has appeared. ... 

Krief et al. have shown that selenium ylides behave as their sulfur analogues and convert a variety of carbonyl compounds to oxiranes <89H(28)1203>. The latter compounds can be directly obtained by using R2Se=CHR /i-hydroxyalkylselenides (available from carbonyl compounds by addition of RSeCH2Li) may serve as suitable precursors as well, either in a two-step protocol, via the selenonium salt by alkylation with magic methyl (MeS03F), or directly by treatment with thallous ethoxide in chloroform. Oxidation of the /t-hydroxyalkylselenides with peracid, followed by treatment of the resulting selenone with base, results in oxirane formation (Scheme 60). 

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