Peroxygen oxidation

A good example of the competitiveness between chlorine and peroxygen oxidants is the preparation of rubber accelerators such as sulphenamides. Sulphenamides are prepared by the oxidative coupling of a mercaptan with an amine (Fig. 1). 

From a mechanistic point of view it is important to realize that polyoxometalates may interact with peroxygen oxidants in several different ways depending on the composition, structure, and redox potential of the polyoxometalate compounds. On the one hand, one may expect reaction pathways typical for any oxotungstate or... 

The peroxygen compounds, hydrogen peroxide and peracetic acid, have high killing activity and a broad spectrum against bacteria, spores, viruses, and fungi when used in appropriate concentration. They have the advantage that their decomposition products are not toxic and do not injure the environment. They are powerful oxidizers that are used primarily as disinfectants and sterilants. 

Doerge DR, Corbett MD (1991) Peroxygenation mechanism for chloroperoxidase-catalyzed N-oxidation of arylamines. Chem Res Toxicol 4 556-560... 

The facile oxidation of organic substrates in the presence of a Fenton system is believed to be due to the production of the hydroxyl radical, as mentioned earlier. Consequently, a number of techniques have been employed to generate the species independently of any iron centres. Two techniques worthy of a mention are photolysis and radiolysis. Photolytic activation can be used to cause homolysis of the peroxygen bond because peroxides have a relatively broad absorption band above 300 nm (Figure 2.13).29... 

Metal oxene compounds are formed from the interaction of a metal centre with a peroxygen and this reaction is classed as a two-electron transfer oxidation (Figure 2.16). 

The oxidation of alchols can be readily carried out using peroxygen reagents. The extensive range of methods available makes it possible to achieve the oxidation of a wide variety of both aliphatic and aromatic primary and secondary alcohols, often in a highly selective manner. 

A number of other peroxygen based methods are known for alcohol oxidations. These include both organic peroxides, such as i-butyl hydroperoxide, and inorganic species such as perdisulfates. In all cases, the presence of metal species to catalyse the reaction is required. 

Figure 3.40 Two competing pathways operating during the oxidation of aldehydes with peroxygen species.

A number of other peroxygen reagents have been used for aldehyde oxidation. In particular, solid adducts of hydrogen peroxide such as urea-hydrogen peroxide (UHP) can generate peracids conveniently in situ.230 This can be applied to the oxidation of benzaldehydes (Figure 3.47). The products are those expected to form typical peracid reactions and are obtained under mild conditions in good yield. 

Organic peroxygen compounds other than peracids have not found wide use in aldehyde oxidation, although some examples of the use of organic hydroperoxides, including /-butyl peroxides (TBHP) and 2-hydroperoxyhexafluoro-propan-2-ol have been reported.213... 

Ketones may be oxidized by peroxygen species under a range of conditions. The most common reaction involves the formation of esters, or in the case of cyclic ketones, lactones. This is known as the Baeyer-Villiger reaction.232-235 This reaction can occur under acidic or alkaline conditions (Figure 3.49), first outlined by Criegee.236... 

Peroxygen systems have three distinct advantages in industrial side chain oxidation compared to the employment of air. Firstly, the reactions can be conducted at atmospheric pressure, and moderate temperature, which makes this an option for small- to medium-volume production in general purpose (low cost) plant. Secondly, the selectivity to produce alcohols or aldehydes is easier to... 

The oxidation of substituted toluenes to benaldehydes employing the CAB system with solid peroxide sources has also been studied by Jones and coworkers.292 The group screened a range of solid peroxygens in place of aqueous... 

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