Isomerization of pentene

It seems that the acidic cocaialysi is required to assure the rapid isomerization of pentene nitrile (equilibration step) and to promote the addition of 4-penteneniirile to the nuncunjugated double bond by assisting the formation of nickel hydride-type intermediates, since the Lewis acid acts as a cyanide acceptor (9). 

The reaction of T with the geometrical isomers of DMC lead mainly to the T-substituted isomer with configuration similar to the reactant however, there is a 5% trans contamination in the case of T 4- cis-DMC and an 8 % cis contamination in the case of T -f- trans-DMC. In other hot T for H substitution, it was found " that there is retention of the configuration. Here, however, substitution with inversion or late isomerization of the T-substituted parent molecule cannot be distinguished. The activation energy for the thermal isomerization of cis - trans and trans - cis is about 2 kcal mol lower than that of isomerization of pentenes. 

Rate of isomerization versus partial pressure of pentene. The slope gives the observed reaction order a = 0.5 for the isomerization of pentene... 

Tetrachloropalladate(II) ion catalyzes the interconversion of 1- and 2-butenes in aqueous solutions containing chloride and hydronium ions. Sodium tetrachloropalladate(II) catalyzes the conversion of allylbenzene to propenyl-benzene in acetic acid solutions. Tetrakis(ethylene))Lt,/x -dichlororhodium(l) catalyzes butene isomerization in methanolic hydrogen chloride solutions . Cyclooctadienes isomerize in benzene-methanol solutions of dichlorobis-(triphenylphosphine)platinum(11) and stannous chloride. Chloroplatinic acid-stannous chloride catalyzes the isomerization of pentenes. Coordination complexes of zero-valent nickel with tris(2-biphenylyl)phosphite or triphenyl-phosphine catalyze the isomerization of cis-1,2-divinylcyclobutane to a mixture of c/5,m-l, 5-cyclooctadiene and 4-vinylcyclohexene . Detailed discussions of reaction kinetics and mechanisms appear in the papers cited. 

Figure 4.10c. The calculated energy diagram for the isomerization of pentene to adsorbed isobutene .

Unimolecular reactions that take place by way of cyclic transition states typically have negative entropies of activation because of the loss of rotational degrees of freedom associated with the highly ordered transition state. For example, thermal isomerization of allyl vinyl ether to 4-pentenal has AS = —8eu. ... 

Isomerization of fluoroolefins by a shift of a double bond is catalyzed by halide 10ns [7] The presence of crown ether makes this reaction more efficient [74] Prolonged reaction time favors the rearranged product with an internal double bond (equations 3-5) Isomerization of perfluoro-l-pentene with cesium fluoride yields perfluoro-2-pentenes in a Z ratio of 1 6 [75] Antimony pentafluoride also causes isomenzation of olefins leading to more substituted products [76]... 

The extent of double-bond isomerization over homogeneous catalysts is influenced by choice of solvent. Saturation of the double bond in 4-(4-me-thoxyphenyl)-3-(2 nitro-4-methoxyphenyl)-l-pentene was achieved smoothly by reduction over RhCl(Ph3P)j in benzene wiihout any hydrogenation of the nitro function. If the solvent were benzene-ethanol, isomerization of the double bond to a conjugated position also occurred ihis styryl bond was inert to reduction under these conditions (77). 

The next step is the isomerization of 2-methyl-1-pentene to 2-methyl-2-pentene using an acid catalyst. 

Another difference between the two mechanisms is that the former involves 1,2 and the latter 1,3 shifts. The isomerization of 1-butene by rhodium(I) is an example of a reaction that takes place by the metal hydride mechanism, while an example of the TT-allyl complex mechanism is found in the Fe3(CO)i2 catalyzed isomerization of 3-ethyl-l-pentene. " A palladium acetate or palladium complex catalyst was used to convert alkynones RCOCSCCH2CH2R to 2,4-alkadien-l-ones RCOCH= CHCH = CHCHR. ... 

Mordenite Isomerization of 2-methyl-2-pentene Higher activity [78]... 

Sandelin, F., Salmi, T., and Murzin, D. (2006) Dynamic modelling of catalyst deactivation in fixed bed reactors skeletal isomerization of 1-pentene on ferrierite. Ind. Eng. Chem. Res., 45, 558-566. 

Ligand screening experiments were conducted on the alkenes 1-pentene and pent-4-en-l-ol, because such substrates were inert to 3a-3c (15). Pentene lacks any polar or protic group and pentenol contains the alkene and OH separated by 3 carbons. The preliminary studies involved phosphines with both imidazol-2-yl and pyrid-2-yl substituents on P as well as t-Bu, i-Pr, Ph, and Me groups (16). From the screening, complex 1 derived from the phosphine ligand 4 (17) was identified as the most capable (in terms of both reaction rate and final yield) of promoting isomerization of both 1-pentene and pent-4-en-l-ol. 

Yang has observed that cis-trans isomerization of 3-methyl-2-pentenes is accompanied by oxetane formation and concluded that intermediates such as (22) are common to both isomerization and oxetane formation/825 Deuterium isotope effects are also consistent with the involvement of this type of intermediate/83,845 ... 

As shown in Fig. 13, a variety of metal carbonyls upon sonication will catalyze the isomerization of 1-pentene to cis- and tram-2-pentene (186). Initial turnover rates are about 1-100 mol 1-pentene isomerized/mol of precatalyst/hour, and represent rate enhancements of 102 5 over thermal controls (174). The relative sonocatalytic and photocatalytic activities of these carbonyls are in general accord. An exception is Ru3(CO)12, which is... 

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... 

Cowley, M. 2006. Skeletal isomerization of Fischer-Tropsch-derived pentenes The effect of oxygenates. Energy Fuels 20 1771-76. 

In favorable cases for some single olefmic species, thermodynamic equilibria with respect to double-bond position can be attained at low temperatures without significant oligomerization. For example, ris-2-bu-tene has been isomerized with the P(CH3)3-modified catalyst at -20°C to give the thermodynamic equilibrium mixture having the composition 78.8% trarts-2-butene, 19.5% m-2-butene, and 1.7% 1-butene. The isomerization of 4-methyl-1-pentene (or of 2-methyl-1-pentene) in the presence of the same catalyst at 0°C also leads to the thermodynamic equilibrium mixture with the composition shown in Table II. If the reaction is carried out at low temperature, the individual isomerization steps can be followed At -58°C, isomerization to ci i-4-methyl-2-pentene occurs and is followed by isomerization to the trans isomer this is then con-... 

A second observation was the fact that isomerization of the starting asymmetric olefin was much faster than the formation of new symmetric olefins. In fact, 40% of the initial cis olefin (Fig. 1) had isomerized to trans after only 4% conversion to new olefins. This result formally parallels the highly selective regenerative metathesis of a-olefins (60, 61), except that steric factors now prevail, because electronic effects should be minimal. Finally, the composition of the initially formed butene from r/j-4-methyl-2-pentene was essentially identical to that obtained when cA-2-pentene was used (18). When tra .v-4-methyl-2-pentene was metath-esized (Fig. 2), the composition of the initially formed butenes indicated a rather high trans specificity. 

The rapid isomerization of c/s-4-methyl-2-pentene relative to productive metathesis suggests further information regarding the isomerization process. If regenerative metathesis proceded selectively via an isopropyl carbene. and assuming that the isopropyl groups maintained equatorial... 

C5 Pentesom [Pentene isomerization] A process for isomerizing linear pentenes to isopentenes, catalyzed by a zeolite. The isopentenes are intended for use as intermediates in the production of ethers for use as fuel additives. Developed by UOP in 1992 and offered for license in 1993. See also C4 Butesom. 

A closer examination by ex situ analysis using NMR or gas chromatography illustrates that intrazeolite reaction mixtures can get complex. For example photooxygenation of 1-pentene leads to three major carbonyl products plus a mixture of saturated aldehydes (valeraldehyde, propionaldehyde, butyraldehyde, acetaldehyde)38 (Fig. 33). Ethyl vinyl ketone and 2-pentenal arise from addition of the hydroperoxy radical to the two different ends of the allylic radical (Fig. 33). The ketone, /i-3-penten-2-one, is formed by intrazeolite isomerization of 1-pentene followed by CT mediated photooxygenation of the 2-pentene isomer. Dioxetane cleavage, epoxide rearrangement, or presumably even Floch cleavage130,131 of the allylic hydroperoxides can lead to the mixture of saturated aldehydes. 

Molybdenum complexes A (Figure 3.46) react efficiently with terminal and internal alkenes in toluene (e.g. 500 eq. Z-2-pentene are metathesized in 2 min at 25 °C 20 eq. of styrene in 2 h at 25 °C). These catalysts also oligomerize 2,4-hexadiene [808] and 1,5-hexadiene [809] and promote RCM of enol ethers. Isomerization of alkenes by catalysts A is a potential catalytic side-reaction [810-812]. 

Karapinka and Orchin (18) made an extensive study of the isomerization of 1-pentene under stoichiometric hydroformylation conditions. 

Most of the work with alumina was done, however, attempting to elucidate the nature of the catalytically active sites in dehydrated alumina. The catalytic activity of alumina is enhanced by treatment with hydrofluoric acid. Oblad et al. (319) measured a higher activity in the isomerization of 1- and 2-pentene. Webb (339) studied the effect of HF treatment on ammonia adsorption by alumina. There was no difference in the capacity. However, the ammonia was more easily desorbed at a given temperature from the untreated sample. Apparently, the adsorption sites grew more strongly acidic by the treatment. No NH4+ ions, only NHj molecules were detected by their infrared spectra, indicating that the ammonia was bound by Lewis acids rather than Bronsted acids. 

The isomerization of light olefins is usually carried out to convert -butenes to isobutylene [12] with the most frequently studied zeolite for this operation being PER [30]. Lyondell s IsomPlus process uses a PER catalyst to convert -butenes to isobutylene or n-pentenes to isopentene [31]. Processes such as this were in larger demand to generate isobutene before the phaseout of MTBE as a gasoline additive. Since the phaseout, these processes often perform the reverse reaction to convert isobutene to n-butenes which are then used as a metathesis feed [32]. As doublebond isomerization is much easier than skeletal isomerization, most of the catalysts below are at equilibrium ratios of the n-olefins as the skeletal isomerization begins (Table 12.5). 

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