2,3,4-trimethylpentane, reaction

Esters. The monoisobutyrate ester of 2,2,4-trimethyl-1,3-pentanediol is prepared from isobutyraldehyde ia a Tishchenko reaction (58,59). Diesters, such as trimethylpentane dipelargonate (2,2,4-trimethylpentane 1,3-dinonanoate), are prepared by the reaction of 2 mol of the monocarboxyhc acid with 1 mol of the glycol at 150—200°C (60,61). The lower aUphatic carboxyHc acid diesters of trimethylpentanediol undergo pyrolysis to the corresponding ester of 2,2,4-trimethyl-3-penten-l-ol (62). These unsaturated esters reportedly can be epoxidized by peroxyacetic acid (63). 

Propylene. Propylene alkylation produces a product that is rich in dimethylpentane and has a research octane typically in the range of 89—92. The HF catalyst tends to produce somewhat higher octane than does the H2SO4 catalyst because of the hydrogen-transfer reaction, which consumes additional isobutane and results in the production of trimethylpentane and propane. 

The alkylate contains a mixture of isoparaffins, ranging from pentanes to decanes and higher, regardless of the olefins used. The dominant paraffin in the product is 2,2,4-trimethylpentane, also called isooctane. The reaction involves methide-ion transfer and carbenium-ion chain reaction, which is cataly2ed by strong acid. 

A solution of 25.8 g. (0.20 mole) of 4-amino-2,2,4-trimethyl-pentane (ierf-octylamine) (Note 1) in 500 ml. of C.P. acetone is placed in a 1-1. three-necked flask equipped with a Tru-Bore stirrer and a thermometer and is diluted with a solution of 30 g. of magnesium sulfate (Note 2) in 125 ml. of water. Potassium permanganate (190 g., 1.20 moles) is added to the well-stirred reaction mixture in small portions over a period of about 30 minutes (Note 3). During the addition the temperature of the mixture is maintained at 25-30° (Note 4), and the mixture is stirred for an additional 48 hours at this same temperature (Note 5). The reaction mixture is stirred under water-aspirator vacuum at an internal temperature of about 30° until most of the acetone is removed (Note 6). The resulting viscous mixture is steam-distilled approximately 500 ml. of water and a pale-blue organic layer are collected. The distillate is extracted with pentane, the extract is dried over anhydrous sodium sulfate, and the pentane is removed by distillation at atmospheric pressure. The residue is distilled through a column (Note 7) at reduced pressure to give 22-26 g. (69-82%) of colorless 4-nitro-2,2,4-trimethylpentane, b.p. 53-5473 mm., < 1.4314, m.p. 23.5-23.7°. 

The results are discussed in terms of strength and number of protonic sites and the presence of mesoporosity is shown to be important for the production of trimethylpentanes in the alkylation reaction. 

Neopentane does not undergo isomerization 185) on chromia/alumina (non-acidic) at 537°C, the only significant reaction been hydrogenolysis to methane and iso-C4. However, the reality of isomerization is made clear from, for instance, the formation of xylenes from 2,3,4-trimethylpentane. For o- and p-xylene, the reactions are (24) and (25) 182, 93). These processes are formally quite analogous to those we have described in previous... 

Observed product distributions, however, make it clear that there must exist reaction pathways in addition to those of the sort in (24) and (25). Thus m-xylene is also a product from 2,3,4-trimethylpentane. This is illustrative of a reaction for which an adsorbed cyclo-C4 intermediate has been suggested (89, 95, 98, 8,185,188, 189). 

The products for which the cyclo-C4 isomerization intermediate has been suggested, can also be explained by a sequence of vinyl insertions. Thus, two vinyl insertions would be adequate to explain the formation of m-xylene from 2,3,4-trimethylpentane. Although we have seen in previous sections that extensive reaction sequences are possible on platinum, isomerization by a single vinyl insertion process on chromium oxide is relatively difficult, and the chance of two occurring in sequence would therefore be expected to be very low. In fact, the proportion of m-xylene is comparable to that of o- and p-xylene. 

Table I gives the compositions of alkylates produced with various acidic catalysts. The product distribution is similar for a variety of acidic catalysts, both solid and liquid, and over a wide range of process conditions. Typically, alkylate is a mixture of methyl-branched alkanes with a high content of isooctanes. Almost all the compounds have tertiary carbon atoms only very few have quaternary carbon atoms or are non-branched. Alkylate contains not only the primary products, trimethylpentanes, but also dimethylhexanes, sometimes methylheptanes, and a considerable amount of isopentane, isohexanes, isoheptanes and hydrocarbons with nine or more carbon atoms. The complexity of the product illustrates that no simple and straightforward single-step mechanism is operative rather, the reaction involves a set of parallel and consecutive reaction steps, with the importance of the individual steps differing markedly from one catalyst to another. To arrive at this complex product distribution from two simple molecules such as isobutane and butene, reaction steps such as isomerization, oligomerization, (3-scission, and hydride transfer have to be involved.

Only large-pore zeolites exhibit sufficient activity and selectivity for the alkylation reaction. Chu and Chester (119) found ZSM-5, a typical medium-pore zeolite, to be inactive under typical alkylation conditions. This observation was explained by diffusion limitations in the pores. Corma et al. (126) tested HZSM-5 and HMCM-22 samples at 323 K, finding that the ZSM-5 exhibited a very low activity with a rapid and complete deactivation and produced mainly dimethyl-hexanes and dimethylhexenes. The authors claimed that alkylation takes place mainly at the external surface of the zeolite, whereas dimerization, which is less sterically demanding, proceeds within the pore system. Weitkamp and Jacobs (170) found ZSM-5 and ZSM-11 to be active at temperatures above 423 K. The product distribution was very different from that of a typical alkylate it contained much more cracked products trimethylpentanes were absent and considerable amounts of monomethyl isomers, n-alkanes, and cyclic hydrocarbons were present. This behavior was explained by steric restrictions that prevented the formation of highly branched carbenium ions. Reactions with the less branched or non-branched carbenium ions require higher activation energies, so that higher temperatures are necessary. 

The bi-functional conversion of 2,2,4-trimethylpentane over Pt/DAY has been recently reported by Jacobs et al. (104). It was compared to the corresponding conversion over Pt/H-ZSM-5 and Pt/H-ZSM-11. All three zeolites had the same chemical composition. The authors found that 2,2,4-trime-thylpentane underwent 3-scission over Pt/DAY, while the formation of feed isomers was favored over the other two catalysts. The differences in reaction products were related to differences in the pore geometry of the zeolites. A similar study was carried out with n-decane. 

Despite the fact that Diels and Alder carried out a cycloaddition in water [2], it was not until 1980 that it was reported that large accelerations in the rates of the Diels-Alder reaction could be achieved in water [3], In addition, selectivity towards the endo product was also increased [4], For example, a 700-fold acceleration in the rate of reaction between cyclopentadiene and 3-buten-2-one (Scheme 7.3) was found in water as compared to reaction in 2,2,4-trimethylpentane. The addition of lithium chloride as a salting-out reagent... 

The 1-butene conversion and product distribution obtained at 25°C after 1 h of alkylation reaction of isobutane on JML-I50 and Beta catalysts are summarized in Table 6.1. The conversion (97%) with JML-I50 catalyst is higher than that (86%) with zeolite Beta. The primary products with the above catalysts are Cs compounds (59.9% with JML-I50 and 62% with Beta). The Cg products mainly consist of trimethylpentanes (TMPs), 58.7% for JML-I50 and 73% for zeolite Beta. The TMP/DMH (dimethylhexane) ratios are 13.5 for JLM-I50 and 4.1 for Beta, demonstrating that the selectivity of JML-I50 is higher than that of zeolite Beta. The yields of alkylate are 6.6 mL and 5.2 mL for JML-I50 and Beta zeolite, respectively. The weights of alkylate produced per weight of butene fed to the reactor are 1.13 and 0.95 for JML-I50 and zeolite Beta, respectively. 

Paraffin alkylation involves the add-catalyzed addihon of an olefin to a branched paraffin to give a highly branched, paraffinic product The representahve reaction is that of isobutane with 2-butene to give 2,2,4-trimethylpentane ... 

Products identified from the reaction of 2,2,4-trimethylpentane with OH radicals in the presence of nitric oxide included acetone, 2-methypropanal, 4-hydroxy-4-methyl-2-pentanone, and hydroxy nitrates (Tuazon et al., 2002). 

Photolytic. Atkinson (1990) reported a rate constant of 7.0 x 10 cmVmolecule-sec for the reaction of 2,3,4-trimethylpentane and OH radicals in the atmosphere at 298 K. Based on this reaction rate constant, the estimated lifetime is 20 h (Altshuller, 1991). 

The restriction for a nucleophile to penetrate and react with the confined cation-radical sometimes leads to unexpected results. Comparing the reactions of thianthrene cation-radicals, Ran-gappa and Shine (2006) refer to the zeolite situation. When thianthrene is absorbed by zeolites, either by thermal evaporation or from solution, thianthrene cation-radical is formed. The adsorbed cation-radical is stable in zeolite for a very long time. If isooctane (2,2,4-trimethylpentane) was used as a solvent, tert-butylthianthrene was formed in high yield. The authors noted it is apparent that the solvent underwent rupture, but the mechanism of the reaction remains unsolved. ... 

Electron attachment rates have been measured for numerous solutes. Many of these studies were limited to three solvents cyclohexane, 2,2,4-trimethylpentane, and tetrame-thylsilane (TMS), and those rates are discussed here. What to expect in other liquids can be inferred from these results. Considerable insight has been gained into certain reactions. Equilibrium reactions of electrons are particularly interesting since they provide information not only on energy levels, as mentioned above, but also on the partial molar volume of trapped electrons. This has led to a better understanding of the mechanism of electron transport. 

Many attachment reactions have been studied in 2,2,4-trimethylpentane, a liquid for which jUd is 6.6 cm /Vs at room temperature. Attachment rate constants for many solutes in 2,2,4-trimethylpentane are shown in Fig. 7 plotted vs. AGr(/). The dotted line shows the diffusion rate for the radius of 0.72 nm, derived for cyclohexane. In 2,2,4-trimethylpentane, only a few solutes, like SFg, CgFg, and the metal carbonyls, come close to the diffusion rate. 

Figure 9 Rate constants for electron attachment to CO2 vs. the free energy of reaction in different fluids 0—2,2,4-trimethylpentane [126], —2,2-dimethylbutane [139], O— TMS [126], —supercritical ethane [99],...

Photochemical irradiation of (i-Pr3Si)3SiH (14) with light of 254 nm in either 2,2,4-trimethylpentane or pentane leads to the elimination of f-Pr3SiH and the generation of bis(triisopropylsilyl)silylene (/-Pr3Si)2Si (15). Silylene 15 can also be generated by the thermolysis of the same precursor 14 at 225 °C in 2,2,4-trimethyl-pentane (Scheme 14.11). Reactions of 15 include the precedented insertion into an Si H bond, and additions to the ti bonds of olefins, alkynes, and dienes. 

H. Schlaad, K. Erentova, R. Faust, B. Charleux, M. Moreau, J.-P. Vairon, and H. Mayr, Kinetic study on the capping reaction of living polyisobutylene with 1,1-diphenylethylene. 1. Effect of temperature and comparison to the model compound 2-chloro-2,4,4-trimethylpentane, Macromolecules, 31(23) 8058-8062, November 1998. 

Isopentane and trimethylpentanes (C8 alkanes) are inevitably formed whenever isobutane is alkylated with any alkene. They are often called abnormal products. Formation of isopentane involves the reaction of a primary alkylation product (or its carbocation precursor, e.g., 3) with isobutane. The cation thus formed undergoes alkyl and methyl migration and, eventually, P scission ... 

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