Hydroperoxides branched alkyl

Figure 6 shows the variation of peroxide concentration in methyl ethyl ketone slow combustion, and similar results, but with no peracid formed, have been found for acetone and diethyl ketone. The concentrations of the organic peroxy compounds run parallel to the rate of reaction, but the hydrogen peroxide concentration increases to a steady value. There thus seems little doubt that the degenerate branching intermediates at low temperatures are the alkyl hydroperoxides, and with methyl ethyl ketone, peracetic acid also. The tvfo types of cool flames given by methyl ethyl ketone may arise from the twin branching intermediates (1) observed in its combustion. 

The /-butyl alcohol can be used to increase the octane number of unleaded gasoline or it can be made into methyl t-butyl ether (MTBE) for the same application. The alcohol can also be dehydrated to isobutylene, which in turn is used in alkylation to give highly branched dimers for addition to straight-run gasoline. An alternative reactant in this method is ethylbenzene hydroperoxide. This eventually forms phenylmethylcarbinol along with the propylene oxide, and the alcohol is dehydrated to styrene. Thus, the yield of the by-product can be varied depending on the demand for substances such as /-butyl alcohol or styrene. 

There is ample experimental evidence for the formation of alkyldihydro-peroxides, especially from the longer chain n-alkanes (Section 6.5) but, as noted in Chapter 1, the rate of chain branching which arises from the homolysis of molecular hydroperoxides, regardless of whether they are alkyl hydroperoxides or dihydroperoxides, is too slow to account for the short duration of ignition delays in high-pressure gases at low-temperature. There is also experimental evidence for the formation of alkylketohydro-peroxy radicals of the form... 

An added advantage of the TS-1 catalyst, which could have commercial benefits, is the possibility for accomplishing shape-selective epoxidations. Owing to the limited dimensions (5.6 A X 5.4 A) of its micropores, linear olefins are epox-idized much faster than branched or cyclic olefins, e.g., 1-hexene is smoothly epoxidized while cyclohexene is virtually unreactive [45]. This reactivity is completely the opposite to that observed with the metal catalyst-alkyl hydroperoxide reagents (see earlier). It could be utilized in, for example, the selective epoxidation of linear olefins in mixtures of linear and branched or cyclic olefins. 

Of course, in special cases when the modeling is aimed at the formation of higher hydrocarbons (Marinov et al., 1996 Mims et al., 1994), their reactions must be included. However, due to a relatively low concentration of these compounds, the requirements to the complete accounting of their reactions can be not very strict due to their relatively low importance. A typical example of such kind could be a chain-branching at the expense of hydroperoxides containing higher alkyl-groups. 

Transition Metai-Catalyzed Epoxidation with Alkyl Hydroperoxides. Alkyl hydroperoxides are attractive oxidants on a technical scale because they can be produced by autoxidation of branched alkanes with oxygen. This concept has been realized on the largest scale in the so-called Halcon process, i.e., the transition metal-catalyzed epoxidation of propylene to propylene oxide (35) (Fig. 9). Homogeneous and heterogeneous titanium, vanadium, and molybdenum catalysts are capable of catalyzing the C=C-epoxidation by alkyl hydroperoxide (for a review see Ref. 36). 

Preventive and secondary antioxidants decompose hydroperoxides without intermediate formation of free radicals, preventing chain branching [20]. They are termed secondary because their best performance is achieved in the presence of primary antioxidants. They also contribute to melt flow and odor stabilization during processing. Aliphatic phos-ph(on)ites esters act only as secondary HD antioxidants while sterically hindered ortho-tcrt-alkylated aromatic compounds are capable of acting also as a primary radical chain breaking reaction. 

Phosphite and phosphonite esters act as antioxidants by three basic mechanisms depending on their structure (1). Basically, phosphites and phosphonites are secondary antioxidants that decompose hydroperoxides. Their performance in hydroperoxide decomposition decreases from phosphonites, alkyl phosphites, aryl phosphites, down to hindered aryl phosphites. Five membered cyclic phosphites act catalytically by the formation of acidic hydrogen phosphates. In contrast, hindered aryl phosphites are interrupting the branched kinetic chain. 

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