2.4- Dimethylpentane, oxidation

Rust [55] studied the oxidation of branched alkanes and was the first to observe the formation of dihydroperoxides as primary products of the hydrocarbon oxidation [55], Dihydroperoxide was found to be the main product of 2,4-dimethylpentane oxidation by dioxygen at 388 K ... 

The peroxyl radical of a hydrocarbon can attack the C—H bond of another hydrocarbon. In addition to this bimolecular abstraction, the reaction of intramolecular hydrogen atom abstraction is known when peroxyl radical attacks its own C—H bond to form as final product dihydroperoxide. This effect of intramolecular chain propagation was first observed by Rust in the 2,4-dimethylpentane oxidation experiments [130] ... 

Tricarbonyl[t/M-(ethoxycarbonyl)-l//-azepine]iron(0) (30) with the 2-oxyallyl cation derived from 2,4-dibromo-2,4-dimethylpentan-3-one and nonacarbonyldiiron(O) yields a mixture of adducts which, after oxidative decomplexation with tetrachloro-l,2-benzoquinone (o-chloranil), affords the tetrahydrofuro[2,3-A)azcpine derivative 33 and the 3-substituted 1H-azepine-l-carboxylate 34.227... 

During PP oxidation, hydroxyl groups are formed by the intramolecular isomerization of alkyl radicals. Since PP oxidizes through an intense intramolecular chain transfer, many of the alkyl radicals containing hydroperoxy groups in the 0-position to an available bond can undergo this reaction. An isomerization reaction has also been demonstrated for the liquid-phase oxidation of 2,4-dimethylpentane [89], Oxidation products contain, in addition to hydroperoxides, oxide or diol. 

UN 1206, see 3,3-Dimethylpentane Heptane UN 1208, see 2,2-Dimethylbutane, 2,3-Dimethylbutane, Hexane, 2-Methylpentane UN 1212, see Isobutyl alcohol UN 1213, see Isobutyl acetate UN 1218, see 2-Methyl-l,3-butadiene UN 1220, see Isopropyl acetate UN 1221, see Isopropylamine UN 1224, see 3-Heptanone, 2-Hexanone, Isophorone UN 1229, see Mesityl oxide UN 1230, see Methanol UN 1231, see Methyl acetate UN 1232, see 2-Butanone UN 1233, see sec-Hexyl acetate... 

There is related evidence from the studies by Rust (13) on the oxidations of neat 2,3- and 2,4-dimethylpentanes that the strain energy in the five-membered ring is higher than 6.3 kcal. Rust found mainly diperoxy compound from the oxidation of the 2,4-isomer, showing that the internal hydrogen atom abstraction from the y-carbon atom competes favorably (/— 19-fold faster) with external abstraction of a similar hydrogen atom. With estimated A-factors of 1010-8 sec."1 and 108 3 liter/mole-sec., respectively for the internal and external abstractions and an effective liquid phase concentration of tertiary C—H bonds of lOAf, we predict a ratio... 

It was observed that 4,4-dimethyl-2-pentene was more readily oxidized than the saturated hydrocarbon—2,2-dimethylpentane—although the latter gave a significantly larger ion yield. In the case of this olefin, which was used as the stereoisomeric mixture, the cis and trans isomers were equally attacked in terms of hydrocarbon oxidized. 

Using chromium-based oxidants 2,4-Dimethylpentane-2,4-diol chromate(VI) diester, 122 Trimethylsilyl chlorochromate, 327 Using other oxidizing agents... 

Using chromium-based oxidants 2,4-Dimethylpentane-2,4-diol chromate(VI) diester, 122 Trimethylsilyl chlorochromate, 327 Using other oxidizing agents Bis(tributyltin) oxide, 41 Hydrogen hexachloroplatinate(IV)-Copper(II) chloride, 145 4-Methoxy-2,2,6,6-tetramethyl-1 -oxopiperidinium chloride, 183 Osmium tetroxide, 222 Potassium nitrosodisulfonate, 258 Samarium(II) iodide, 270 From alkenes by addition or cleavage reactions... 

The complex [PtCl2(DIOP)] in the presence of SnCl2 has been used as catalyst for the asymmetric hydroformylation of various alkenes. With a series of butene and styrene derivatives very low optical yields were obtained. The best results were achieved with 2,3-dimethyl-l-butene which gave 15% optically pure 3,4-dimethylpentanal, and with a-ethylstyrene which gave 15% optically pure 3-phenylpentanoic acid after oxidation of the aldehyde.373... 

Corey et al reported that the complex formed by chromium VI) oxide and 2,4-dimethylpentane-... 

Corey et al reported that the complex formed by chromium(VI) oxide and 2,4-dimethylpentane-2,4-diol can be used as a catalytic oxidant with peroxyacetic acid as a cooxidant. When used stoichiome-trically, secondary alcohols are oxidized quickly even at -20 C, but the oxidation of primary alcohols is slow and large amounts of ester coupling are observed. 

Recently, however, two pieces of direct experimental evidence have become available. First, in a low temperature (100 °C) liquid-phase investigation of the oxidation of 2,4-dimethylpentane Mill [105] found Ai4/5 = 10 ° sec" and ,4 = 15 kcal. mole" for... 

For some of the simple 4,5-dihydro-3//-pyrazoles not available by the diazoalkane-alkene route, an alternative to the hydrazine reaction discussed in the last section is oxidative cyclization of a 1,3-diamine. Hence, an alternative preparation of the ketone 1 is to react 2,4-dibromo-2,4-dimethylpentan-3-one with sodium azide, reduce the azide groups with ammonium polysul-fide " and oxidatively cyclize with sodium hypobromite. " ... 

It was calculated from analysis of y-radiation induced oxidation of 2,4-dimethylpentane [188], using value 15 x 10 3 moll-1 for the concentration of oxygen dissolved in the hydrocarbon, that only around 10% of R available in... 

Abstraction of H from 2,4-dimethylpentane (a model of PP) was proposed [207] as an alternative stabilizing mechanism instead of R trapping in gamma-induced oxidation ... 

The similarity between the CB AO mechanism of phenols and HAS was reported at 25 °C in radiation oxidation of 2,4-dimethylpentane performed in the dark [207]. It was concluded that the respective NOH formed from 28, R = H during the stabilization process was the species responsible for the antioxidant effect (Scheme 27). The NOH is considered to be formed via trapping H by lltNO . The authors declared that i NOR are not involved in the stabilization of the radiation-oxidation of hydrocarbons and have doubts about the importance of the involvement of NOR in the regenerative cycle in an oxygen containing environment. 

It has been observed that the intramolecular propagation plays an important role in the oxidations of 2,4-dimethylpentane (32,33), 2,4,6-trimethylheptane (34), and polypropylene (35,36). However, this intramolecular propagation must be unimportant in PVA oxidation since 2,4-pentanediol did not give 2,4-pentanedione under similar conditions (Run 18). Rust (37) also found no 2,4-pentanedione in the thermal oxidation of 2,4-pentanediol. Table III shows that 4-hydroxy-2-pentanone is the major primary product from 2,4-pentanediol. Therefore, the primary products from PVA must be /3-hydroxyketone and hydrogen peroxide. 

Obtained in 70% yield from CrOj and TiCU in CH2CI2 with ultrasound irradiation for 2.5 h. It can be used in the Etard oxidation or converted into Cr02(0Bu >2 and the cyclic chromate of 2,5-dimethylpentane-2,5-diol for other oxidations. 

The unusual feature of the oxidation of 2,4-dimethylpentane is the formation, even at the lowest measurable conversions, of the dihydroperoxide in yields of over 90%, viz. 

Rust [37] showed that among several branched alkanes which gave difunctional products on oxidation at 120°C, 2,4-dimethylpentane gave the highest yield of the dihydroperoxide and on the basis of this selectivity he proposed that the key reaction involved intramolecular H-atom transfer from C-4 through a sterically favorable six-center transition state... 

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