ROOH-amine systems

Less attention has been paid to the ROOH-amine system, but we [34] have investigated the effect of amine... 

We have proposed an initiation mechanism for the ROOH-amine system in which some H-bond complex may be formed [36]. Then Sun et al. [37,38] thoroughly investigated the initiation mechanism of ROOH-Amine through IR spectra of TBH-triethylamine, TBH-DMT, and CHP-DMT. From the wideness of the shift of OH absorption bands at 3120, 3336, and 3257 cm were... 

Table 5 Rp of MMA Initiated with ROOH-Amine System...

Hydrocarbon oxidation may also be considered a free radical chain-type reaction. At elevated temperatures, hydrocarbon free radicals (R) are formed which react with oxygen lo form peroxy radicals (R(X These, in turn, take up a hydrogen atom from the hydrocarbon to form a hydroperoxide (ROOH) and another hydrocarbon free radical. The cycle repeals itself with the addition of oxygen. The unstable hydroperoxides remaining are the major points for degradation and lead to rancidity and color development in oils, fats, and waxes decomposition and gum formation in gasolines sludging in lubricants and breakdown of plastics and rubber products. Antioxidants, such as amines and phenols, are often introduced into hydrocarbon systems in order lo prevent this free radical oxidation sequence. 

The Ru(II)/ROOH system can also be used to oxidize tertiary amines. The intermediate iminium ion is formed, as described earlier for secondary amines, and can be trapped by nucleophiles. Thus, the ruthenium-catalysed oxidation of tertiary amines with hydrogen peroxide in methanol can be performed to give the corresponding a-methoxyamines with high efficiency as illustrated in Fig. 24 [ 137]. Another example is the selective demethylation of tertiary amines in methanol with a combination of Ru(II) and H202, followed by hydrolysis of the intermediate a-methoxylated amines. For example, the methoxylation of N,N-dimethyl-p-toluidine followed by treatment with 2 N HC1 solution gave N-methyl-p-toluidine in 75% yield (Eq. 35) [137]. 

Fig. 24 Ru(II)/ROOH system in methanol for oxidation of tertiary amines...

Iron porphyrins have been studied extensively over the past 30 + years as model systems of cytochrome P450.13 Biomimetic model studies included variants in axial ligands (thiolate and other bases), the oxidation of alkanes, olefins, sulfides, and amines, and utilization of several oxidants such as hypochlorite (bleach), iodoso-benzene (ArlO), hydrogen peroxide, and organic peroxides (ROOH). The first-generation models employed the mevo-tetraary I porphyrins (Figure 3.5). These were... 

Instead of the dioxygen-reductant pair, one can employ oxo componds containing an oxygen atom which is already partly reduced H2O2 [68], ROOH [69], PhIO [70], NaOCl [71], KHSO. [72], amine Af-oxides [73], and magnesium monoperoxyphtalate [74] (see also Chapter X). One of the most efficient (in terms of reaction rate and turnover number) systems is the combination of ruthenium porphyrin and 2,6-dichloropyridine A-oxide [73]. A simplified mechanism of alkane oxidation with iodosylbenzene catalyzed by iron porphyrinate is demonstrated in Scheme XI. 17. 

In systems where such radicals appear (alcohols, amines, some unsaturated compounds), variable-valence metal ions manifests themselves as catalysts for chain termination (see Chapter 11). The reaction of the ions with peroxyl radicals appears also in the composition of the oxidation products, especially at the early stages of oxidation. For example, the only primary oxidation product of cyclohexane autooxidation is hydroperoxide the other products, in particular, alcohol and ketone, appear later as the decomposition products of hydroperoxide. In the presence of stearates of such metals as cobalt, iron, and manganese, all three products (ROOH, ROH, and ketone) appear immediately with the beginning of oxidation and in the initial period (when ROOH decomposition is insignificant), they are formed in parallel with a constant rate. The ratio of rates of their formation is determined by the catalyst. The reason for this behavior is evidently related to the fast reaction of R02 with the catalyst. Thus, the reaction of peroxyl radicals widi variable-valence ions manifests itself in the kinetics as well (the induction period appears imder certain conditions), and alcohol and ketone are formed in parallel with ROOH from R02 among the oxidation products. 

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