Activation 2-methylpentane

Methylpentane (mixture of isomers). Passage through a long column of activated silica gel (or alumina) gave material transparent down to 200nm by UV. 

Microwave activation of alkane transformations was studied in detail by Roussy et al., who summarized their results in several papers [2, 28, 29, 79]. Isomerization of hexane, 2-methylpentane, 2-methyl-2-pentene, and hydrogenolysis of methylcydo-pentane have been investigated, and the diversity of possible effects has been specified [2]. The course of 2-methylpentane isomerization on a 0.3% Pt/Al203 catalyst depended on the mode of heating - the distribution of hexane products was different... 

Table 3 Arrhenius and Eyring activation parameters for the debrominations of 2,3-dibromo-2-methylpentane (27) and 1,2-dibromodecane (29) with di-n-hexyltelluride (26) and tetra-n-butylammonium iodide...

Benzene formation from all isohexanes had a similar energy of activation value. With platinum this was nearly twice as high as that of n-hexane aromatization (62) with palladium black, however, nearly the same values were found for -hexane and isohexanes (97a). This indicates a common rate-determining step for aromatization with skeletal rearrangement. This is not the formation and/or transformation of the C5 ring. We attribute benzene formation to bond shift type isomerization preceding aromatization. It requires one step for methylpentanes and two steps for dimethyl-butanes this is why the latter react with a lower rate, but with the same energy of activation. 

Fig. 12. A possible accommodation of 3-methylpentane suitable for ring closure assuming positions on the top of metal atoms as active sites 144).

Rate constants have been determined for solvolyses of 2-bromo- (or -chloro-) -2-methylbutane and 3-chloro-3-methylpentane in 10 diols at 298.15 K. By combining kinetic data with thermodynamic data, transfer Gibbs energies of the reactants (initial state) and of the activated complex (transition state) were obtained, which allowed the solvent effects on both states to be quantitatively analysed. 

The reaction of [RhCl(COD)2] and four equivalents of P(CH20H)3 in THF gave cis-[RhH2 P(CH20H)3 4], which actively catalyzed the biphasic hydroformylation of 1-pentene [74]. In a water/benzene mixture, at 100 °C and 40 bar syngas this substrate was quantitatively converted to hexanal (43 % yield) and 2-methylpentanal (57 %) in 20 h. At the [substrate]/[catalyst] ratio of 90 this is equivalent to a minimum TOP of 4.5 h" . The catalyst was recycled in the aqueous phase three times with no changes in its activity or selectivity. 

Rhodium-phosphine catalysts are unable to hydroformylate internal olefins, so much that in a mixture of butenes only the terminal isomer is transformed into valeraldehydes (see 4.1.1.2). This is a field still for using cobalt-based catalysts. Indeed, [Co2(CO)6(TPPTS)2] -i-lO TPPTS catalyzed the hydroformylation of 2-pentenes in a two-phase reaction with good yields (up to 70%, but typically between 10 and 20 %). The major products were 1-hexanal and 2-methylpentanal, and n/i selectivity up to 75/25 was observed (Scheme 4.12). The catalyst was recycled in four mns with an increase in activity (from 13 to 19 %), while the selectivity remained constant (n/i = 64/36). 

The hexasila-Dewar benzene 13 is thermally stable at —150 °C, but it gradually reverted to the hexasilaprismane 1243. The half-life is 11/2 = 0.52 min at 0 °C in 3-methylpentane. The activation parameters for the isomerization of 13 to 12 are a = 13.7 kcalmol-1, A= 13.2 kcalmol-1 and A= — 17.8 cal K-1 mol-1. The small Ea value is consistent with the high reactivity of Si=Si double bonds. Most probably, the small HOMO-LUMO gap of 13 makes it possible that the Si=Si double bonds undergo a formally symmetry forbidden [2 + 2] thermal reaction. Hexasila-Dewar benzene is a key... 

Photolytically generated 1-silabuta-l,3-dienes undergo a thermal reverse reaction to 2-silacyclobutenes. Thus 2-phenylsilacyclobut-2-ene 360 is easily opened to the 2-phenylsilabuta-1,3-diene 361 by irradiation in 3-methylpentane matrix at 77 K or by flash photolysis at ambient temperature (equation 97)183. The rate for the thermal reverse reaction was measured at room temperature and the activation energy for the 1 -siladiene ring closure was estimated to be 9.4 kcalmol-1183. 

Component 1 in Singapore buildings was correlated with compounds associated with humans and their activities. Human effluents have been reported to contain isoprene (Ellin et al, 1974) while tetrachloroethylene is a VOC found in dry-cleaned clothes worn by building occupants (Wallace, Pellizzari and Wendel, 1991) or from the use of consumer products (Sack et al., 1992). Tetradecane, benzaldehyde, o-xylene, naphthalene are emissions from dry process photocopiers (Leovic et al., 1996). Component 2 with high loadings ofn-decane, n- undecane, toluene, styrene, n-nonane, 1,2,4-trimethyl benzene probably reflects the emissions of carpets and vinyl floorings (Yu and Crump, 1998). Component 3 was primarily correlated with heptane and methylcyclopentane, which could be due to the emissions of water-based paints. Finally, component 4 was associated with 2-methylpentane, hexane, cyclohexane, methylcyclohexane and limonene, which is reflective of the emissions of air fresheners and cleaning products (Sack et al., 1992). 

Relative hydrogen transfer activity can be determined using an HTI test (11), where the index is a measure of the degree of saturation in the reaction product. The test determines the product ratio of 3-methylpentenes to 3-methylpentane derived from a 1-hexene feed. While the branched products come mainly from oligomerization followed by cracking, the results should be relevant here as well. The higher the index, the lower the relative hydrogen transfer activity. 

The catalytic activities of the modified Na,H-ZSM-5 and the fully protonated H-ZSM-5 were measured for several reactions. The constraint index experiment was carried according to the literature A 1 1 molar mixture of n-hexane and 3-methylpentane was fed over the catalyst bed at 300°C at a rate of 1 ml/hr with a helium diluent at 12.5 ml/min. The effluent stream was sampled after 20 minutes by syringe and analyzed by gas chromatography. The constraint index is given by Equation 5. 

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. 

The noble metal component may be either palladium or platinum the effect of the concentration of both metals on methylpentane as well as on dimethylbutane selectivity in C6 hydroisomerization on lanthanum and ammonium Y-zeolite with Si/Al of 2.5 has been studied by M.A. Lanewala et al. (5). They found an optimum of metal content for that reaction between 0.1 and 0.4 wt.-%. The noble metal has several functions (i) to increase the isomerization activity of the zeolite (ii) to support the saturation of the coke precursors and hence prevent deactivation, as was shown by H.W. Kouvenhoven et al. (6) for platinum on hydrogen mordenite (iii) to support the hydrodesulfurization activity of the catalysts in sulfur containing feedstocks. 

Asymmetric hydroformylation." Optically active aldehydes can be obtained by hydroformylation (CO/H2 = 1 1) of conjugated dienes with HRhfCOjCPfCaHsljjj-(-)-DIOP as catalyst. The highest optical yield (32%) was obtained in the hydroformylation of isoprene to give 3-methylpentanal. 

Recently, AEDA and SHA-0 yielded 41 and 45 odor active compounds for Scheurebe and Gewurztraminer wines, respectively (P). Ethyl 2-methylbutyrate, ethyl isobutyrate, 2-phenylethanol, 3-methylbutanol, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 3-ethylphenol and one unknown compound, named wine lactone, showed high flavor dilution (FD)- factors (Table I) in Gewurztraminer and Scheurebe wines. 4-Mercapto-4-methylpentan-2-one belongs to the most potent odorants only in the variety Scheurebe whereas cis-rose oxide was perceived only in Gewurztraminer (Table I). 4-Mercapto-4-methylpentan-2-one was identified for the first time in Sauvignon blanc wines (JO). The unknown compound with coconut, woody and sweet odor quality, which has not yet been detected in wine or a food, was identified as 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) (JJ). 

The relative activities of ketones formed from 2-methylpentanes (From ref. 113.)... 

Examination of the alkylperoxy radicals which may be formed from 3-ethylpentane, 3-methylpentane and 2-methylpentane shows that, in each case, some may undergo isomerization reactions with relatively low activation energies [58], examples of which are shown in Table 20. 

Estimated activation energies 2-methylpentane [58] for isomerization of some alkylperoxy radicals derived from 3-ethylpentane, 3-methylpentane and... 

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