Methylpentene, isomerization

We made two competitive runs with 2-hexene and 4-methyl-1-pentene. In run 277 on the amorphous catalyst of run 276, Table VI, at a total L of 1550 and an average ratio of methylpentene to 2-hexene of 1.4, the alkane yield was 12.4%. Correction of the alkane ratio by the olefin ratio in the feed (46) indicates that 2-hexene was hydrogenated 0.6 times as fast as methylpentene. Isomerization of methylpentene was negligible and that of 2-hexene, proportionately about as in run 276. 

Microwave irradiation of catalysts before their use in chemical reactions has been found to be a new promising tool for catalyst activation. Microwave irradiation has been found to modify not only the size and distribution of metal particles but probably also their shape and, consequently, the nature of their active sites. These phenomena might have a significant effect on the activity and selectivity of catalysts, as found in the isomerization of 2-methylpentene on a Pt catalyst [2],... 

The formation of 2-methyl and 3-methylpentenes requires long contact times due to the involvement of the primary cation 8. Under such conditions the concentration of the latter two compounds is near the equilibrium and only a very small amount of n-hexenes is detected (Scheme 4.8, b). This, again, indicates that further isomerization of methylpentenes to n-hexenes occurs through a primary cation (9). These distinct changes in product distribution strongly indicate that only 1,2 shifts are involved in skeletal rearrangement under these conditions. 

Dimerization of propylene leads to the formation of isomeric methylpentenes in the presence of alkali metals.34 The product distribution strongly depends on the metal used. 4-Methyl-1-pentene is formed with high selectivity in the presence of potassium and cesium. Because of extensive isomerization, an equilibrium mixture of the isomers with 4-methyl-2-pentene and 2-methyl-2-pentene as the main products was isolated in a reaction catalyzed with sodium. 

The Arrhenius parameters for the gas-phase unimolecular structural isomerizations of 1,1,2-trimethylcyclopropane28 to three isomeric methylpentenes and two dimethyl-butenes, and of 1,1,2,2-tetramethylcyclopropane29 to 2,4-dimethylpent-2-ene have been determined over a wide range of temperatures. Despite previous reports on substantial decreases in activation energies for structural isomerizations of methyl-substituted cyclopropanes, this study has revealed that the trend does not continue beyond dimethylcyclopropane isomerization. 

Bromine fluoride adds exothermally across the C=C bond of F-heptene-1, even F-heptene-2 and F-4-methylpentene-2 (6), but not isomeric F-2-methyl-pentene-2 [51] ... 

Methylbutene-l, 4-methylpentene-1 and 5-methylhexene-l represent a homologous series. Thus, it is conceivable that intramolecular hydride shift polymerization will also occur with the latter two monomers. Indeed NMR spectra seem to suggest that a predominantly 1,4 and 1,5 type isomerization polymerization occurs when 4-methylpentene-1 and 5-methylhexene-l are reacted with catalysts of the Lewis acid type at low temperatures (—73° C.) (163). According to the NMR evidence, low temperature cationic poly(4-methylpentene-l) shows only 2 sharp peaks, characteristic for the CH3 and CH2 groups. This is in agreement with a gem. dimethyl structure of the a,a-dimethylbutane type ... 

Internal perfluoroalkenes react with trimethyl(perfluorophenyl).silanc under more forcing conditions than terminal alkenes. The reactions can also give biphenyl derivatives. An interesting dependence of the reaction results on the structure in the case of perfluorophenylation of isomeric perfluoro(methylpentenes) has been identified. Perfluoro(2-methylpent-2-ene) is transformed into pcrfluoro(2-methyl-3-phenylpent-2-cnc) (4) perfluoro(4-methylpent-2-cnc) forms pcrfluoro( 1.1,3-triinethy lindan) (6) as well as perfluoro(4-inethyl-2-phciiylpen t-2-ene) (5). 

Table IV contains the distribution of the Cc isomers using tri( isopropyl) phosphine as a catalyst component (neglecting isomerization). From the distribution of the products it follows that 13% of terminal (sum of n-hexenes and 4-methylpentene-2) and 84% of middle (sum of 2-methylpentene-l and 2,3-dimethylbutene-l) C—H bonds reacted. Similarly, the direction of addition was roughly 80% of the acidic and 20% of the hydridic type. The direction of addition remains roughly in the...

In run 270, on the crystalline catalyst of runs 267 and 271, L was 4500 the olefin ratio, 1.6 and the alkane yield, 9.2%. Here, 2-hexene hydrogenated 0.2 times as fast as methylpentene. In comparison with run 271, the yield of 4-methyl-2-pentene was slightly reduced but that of 2-methyl-2-pentene was cut nearly to 0.1 of its value in run 271. The degree of isomerization of 2-hexene was close to that in run 272 on a new sample of chromia activated at 400° in hydrogen. 

The isomerization polymerization with material transport makes it possible to distinguish between a polymerization by hydride shift as in 3-methylbutene-l (or 4-methylpentene-l, 4-methylhexene-l, or vinylcyclo-hexane),... 

C for 96 h produced an equilibrium mixture of anhydrides containing 60% 74a, 8% 74b, and 21% 74c. The olefin removed from the mixture also seemed to contain an equilibrium mixture of 2-methylpentene-l (27%) and 2-methylpentene-2 (73%). The effect of temperature on the unreacted olefin composition is shown in Table 5.7. It may be noted that in the absence of MA but using succinic anhydride, only 7% of the isomerized 2-methylpentene-1 was obtained. Thus, direct thermal isomerization of olefin plays an insignificant role. 

The opposite is true of ethylene-4-methylpentene-l copolymers obtained with the catalytic system V acetylacetonate—Al(isoC4H9)2Cl (153). These copolymers contain both units from normal 1,2-addition and isomerized units of the type —CH2—CH2—CH2—C(CH3)2—, diaracterized by the 1230 cm band. 

When Rj is different from R2 in Formula (1.1) the carbon atom is asymmetric and may have d or 7 forms. If all the asymmetric carbon atoms have either d or 7 forms, the polymer chain is said to be isotactic. If these carbon atoms are instead alternating d and 7 , the polymer chain is said to be syndiotactic. If the d and 7 assignments are random along the chain, it is said to be atactic [8,18-20] (see Fig. 1.1). Isotactic polypropylene, poly(butene-l) and poly(4-methylpentene-l) are commercially available. Both isotactic and syndiotactic polypropylene and polystyrene have been synthesized, subjected to extensive investigation. The two isomeric polymers have different crystal structures and their atactic forms do not crystallize. Isotactic and syndiotactic polymers were originally developed by Natta and his coworkers [18, 19] at Milan Polytechnic and Montecatini. In recent years, there has been interest in producing polyolefins with controlled intermediate tacticities [20]. 

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