Methylpentanes, oxidation

Radioactive tracer studies of 2-methylpentane oxidation at 515 K enabled Cullis et al. [200] to show that the overall mechanism was more strongly affected by abstraction from the four secondary C—H sites than fi"om the single tertiary C—H site, despite its lower bond strength. The temperature at which this study was performed would suggest that abstraction by OH radicals might be rather more important than abstraction by HO2 or RO2 radicals. 

Some companies are successfully integrating chemo- and biocatalytic transformations in multi-step syntheses. An elegant example is the Lonza nicotinamide process mentioned earlier (.see Fig. 2.34). The raw material, 2-methylpentane-1,5-diamine, is produced by hydrogenation of 2-methylglutaronitrile, a byproduct of the manufacture of nylon-6,6 intermediates by hydrocyanation of butadiene. The process involves a zeolite-catalysed cyciization in the vapour phase, followed by palladium-catalysed dehydrogenation, vapour-pha.se ammoxidation with NH3/O2 over an oxide catalyst, and, finally, enzymatic hydrolysis of a nitrile to an amide. 

Horstmann, S., Wilken, M., Fischer, K., Gmehling, J. (2004) Isothermal vapor-liquid equilibrium and excess enthalpy data for the binary systems propylene oxide + 2-methylpentane and difluoromethane (R32) + pentafluoroethane (R125). J. Chem. Eng. Data 49,1504-1507. 

These cycloadducts, at their most elementary level, are excellent intermediates for the synthesis of 3-substituted furan derivatives. For example, Kawanisi and coworkers reported a synthesis of perillaketone 174 in which the critical step was a Paterno-BUchi photocycloaddition between furan and 4-methylpentanal in the presence of methanesul-fonic acid (Scheme 39)82. This reaction furnished two initial photoadducts, 172 and 173. The unexpected product 173 presumably arises from a Norrish Type II cleavage of 4-methylpentanal to give acetaldehyde, and subsequent cycloaddition with furan. The desired cycloadduct 172 was then converted uneventfully to 174 via acid-catalyzed aromatization and oxidation. 

The oxidation reactions of 2-methylpentane provide a good example of how the hydroperoxy states are formed and why molecular structure is important in establishing a mechanism. The C—C bond angles in hydrocarbons are about 108°. The reaction scheme is then... 

H, Cl, Br, NO2, Me, MeO) by bromamine-B, catalysed in the presence of HCl in 30% aqueous methanol by RuCls have been smdied and a biphasic Hammett a-relationship derived. A kinetic study of the ruthenium(in)-catalysed oxidation of aliphatic primary amines by sodium A-bromo-j -toluenesulfonamide (bromamine-T, BAT) in hydrochloric acid medium has been undertaken and the mechanism of the reaction discussed. A concerted hydrogen-atom transfer one-electron transfer mechanism is proposed for the ruthenium(in)-catalysed oxidation of 2-methylpentane-2,4-diol by alkaline hexacyanoferrate(III). The kinetics of the oxidation of propane-... 

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... 

LXVIII), a constituent of aviation fuel. The reaction of acetone with acetylene may also lead to developments of importance in finding new uses for acetone. For example, acetone reacts with acetylene in the presence of a metal acetylide catal5rst to form the compound LXIX, which could be converted into isopentane (LXX), another constituent of aviation fuel. There may be possibilities of using the condensation products of acetone such as mesityl oxide (LXXI), which could be converted through the saturated ketone, methyl isobutyl ketone (LXXII), into 4-methylpentane (LXXIII). 

The data in Table 7 show that the selectivity for 2-oxygenated products in the oxidation of alkanes on TS-1 is somewhat higher than could be expected on statistical grounds. Only for 3-methylpentane, this selectivity becomes overcompensated by the higher reactivity of tertiary C-H compared to secondary C-H positions. This indicates that the first step of the oxidation, i.e. the formation of alcohols from alkanes is slightly regioselective. Within the ketone fraction, the selectivity for 2-ketones is even more pronounced, indicating that 2-alcohols are selectively oxidized to 2-ketones in the... 

HLADH oxidation of 3-methylpentane-l,3,5-triol yields, after silver oxide oxidation, (35)-(-l-)-mevalonolactone of 14% optical purity/" The synthesis of [4,5- C2]MVA using known procedures was omitted from last year s Report, " " and another synthesis of ( )-mevalonolactone has been reported. " ... 

During the oxidation of 2-methylpentane, five radicals CeHiaOO will be formed the rearrangement by hydrogen transfer of these can, in theory, produce a total of 21 radicals C HioOOH (24). 

This scheme (in which the reversible arrows are not meant to imply that equilibrium is attained) provides an excellent qualitative, and reasonably semiquantitative, description of the formation of products during the cool-flame oxidation at 523° to 580°K. of 2-methylpentane (24). Also, because of the different energy requirements for the various modes of Reactions 4 and 5, the scheme is capable of explaining, at least in principle, the complex dependence of rate on temperature during cool-flame oxidation (24, 51). 

Conflicting results have been reported for the products obtained in the oxidation of branched hydrocarbons. For 2-methylpentane, reaction at C2 with... 

Cracking and disproportionation in the reaction of hexane could be suppressed by the addition of cycloalkanes (cyclohexane, methylcyclopentane, cyclopentane).101 Furthermore, 3-methylpentane and methylcyclopentane also reduced the induction period. These data indicate that reactions are initiated by an oxidative formation of alkene intermediates. These maybe transformed into alkenyl cations, which undergo cracking and disproportionation. When there is intensive contact between the phases ensuring effective hydride transfer, protonated alkenes give isomerization products. 

The reactions of butane-2,3-diol by HCF in alkaline medium using Ru(III) and Ru(VI) compounds as catalysts leads to similar experimental rate equations for both the reactions. The mechanism involves the formation of a catalyst-substrate complex that yields a carbocation for Ru( VI) or a radical for Ru(III) oxidation. The role of HCF is in catalyst regeneration. The rate constants of complex decomposition and catalyst regeneration have been determined.89 A probable mechanism invoving formation of an intermediate complex has been proposed for the iridium(III)-catalysed oxidation of propane- 1,2-diol and of pentane-1,5-diol, butane-2,3-diol, and 2-methylpentane-2,4-diol with HCF.90-92 The Ru(VIII)-catalyzed oxidation some a-hydroxy acids with HCF proceeds with the formation of an intermediate complex between the hydroxy acid and Ru(VIII), which then decomposes in the rate-determining step. HCF regenerates the spent catalyst.93... 

Methyloxobismuthine, see Methylbismuth oxide, 0427 f 2-Methyl-1,3-pentadiene, 2410 f 4-Methyl-1,3-pentadiene, 2411 f 2-Methylpentanal, 2485 f 3-Methylpentanal, 2486 f 2-Methylpentane, see Isohexane, 2527 f 3-Methylpentane, 2528 f 2-Methyl-2-pentanol, 2539 f 2-Methyl-3-pentanone, 2487 f 3-Methyl-2-pentanone, 2488 f 4-Methyl-2-pentanone, 2489a f 2-Methyl-1-pentene, 2456 f 4-Methyl-1-pentene, 2457 f r .v-4-Methyl-2-pentene, 2458 f tra .v-4-Methyl-2-pentene, 2459 3-Methyl-2-penten-4-yn-1 -ol, 2378 Methyl perchlorate, 0435... 

Janot et al. [90] described the increased hydrogen adsorption of ball-milled Mg2Ni alloys and interpreted their findings with the removal of oxide layers. A Pd-Mg catalyst precursor used for the synthesis of methyl isobutyl ketone was prepared by milling PdO with Mg [91]. Dehydration and dehydrogenation reactions of 4-methylpentan-2-ol over ball-mined catalysts such as CuM (M = Ti, Zr, Hf) have also been investigated [92]. 

The detection limit for gallium determination at 287.4 nm in an air-acetylene flame is only about 70 ng ml - and that by flame AFS is not much better, and sometimes even worse.1 The detection limit by flame AES at 403.3 nm is appreciably better, especially if a nitrous oxide-acetylene flame is used. This reflects the low excitation energy. These values are too low to make the direct determinations useful in environmental applications, and therefore solvent extraction is often used for pre-concentration.1 One method often used is the extraction of the anionic keto-chloro complex from strong hydrochloric acid solution (e.g. 5.5M) into 4-methylpentan-2-one.25,26 Co-extraction of iron may... 

Indium has not proved to be an element of great interest in most environmental samples, in which it is usually present at very low concentrations. The flame AAS determination in a lean air-acetylene flame at 303.9 nm has a detection limit of around 50 ng ml -, and flame AFS is not much better.1 Flame AES in a nitrous oxide-acetylene flame gives a much lower detection limit at 451.1 nm, of around 2 ng ml"1. However the element has a low ionization potential, and addition of potassium at 5 mg ml"1 as an ionization buffer is therefore advised. Sensitivity may be enhanced by solvent extraction pre-concentration using a high extraction ratio.1 Even when pre-concentrated from geological samples by extraction into 4-methylpentan-2-one from 6M hydrochloric acid solution, ICP-AES may be the preferred method of analysis.27... 

These results suggest that if we want to design a molecular sieve to separate a mixture of normal hexane and 2-methylpentane, we should use a zeolite with normal sinusoidal pores but small-diameter straight pores such a zeolite will preferentially accept normal -hexane and preferentially reject 2-methylpentane. More important, perhaps, these results have implications for selective catalysis. If we want -hexane to react but not 2-methylpentane, then we should make a zeolite where the catalytically active centers (aluminum oxides) are situated in the sinusoidal pores but not in the straight pores. Conversely, if we desire preferential catalysis for the branched isomer, we want a zeolite where the active centers are at the intersections between straight and sinusoidal pores. 

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