3- Methyl-1-pentene, carbon

Besides the eight well documented condis phases of flexible, carbon-backbone macro-molecules described in Sects. 4.1 to 4.5, ttere is evidence of an even larger abxmdance of condis crystals as stable phase, intermediate in crystallization, and possibly also on large scale deformation. In this section some indication of the existence of condis phases for aliphatic nylons, polyallene and pofy[(S)-3-methyl-pentene-1] will be reviewed. Lateral and longitudinal disorder was noted much earlier for a larger series of polymers but little is known about the dynamic nature, i.e. if these macromolecules must be considered CD glasses or if they are stable condis crystals at any temperature. 

H2O plasma was used to modify poly(methyl pentene) hollow fiber membranes, making it possible to immobilize an enzyme (carbonic anhydrase) on them. Such treatment significantly improved the respiratory assistance devices for CO2 removal... 

An interesting sidelight of this work is the use of the magnetized carbon described herein as an olefin isomerization catalyst. In the presence of this material we have been able to form thermodynamically less stable methyl pentene isomers at elevated temperatures. 

BBL = -butyrolactone DTC = 2,2-dimethyl tri-methylene carbonate HTC = 2,2-(2-pentene-l,5-diyl)fri-methylene carbonate 1-MeTMC = 1-methyl trimethylene carbonate MMA = methylmethacrylate MMAO = modified methyMuminoxane PBD = polybutadiene PIP = polyiso-prene PHAs = polyhydroxyalkanoate PLA = polylactide ROP = ring-opening polymerization TMC = trimethylene carbonate. 

The cracking pattern given by zinc di (4-methyl 2-pentyl) dithiophosphate is more informative, and the results obtained may be compared with those obtained by Legate and Burnham. Having two beta carbon atoms from which hydrogen may be removed, two olefins are likely to be formed, 4-methyl pentene-1 and 4- methyl pentene-2. 

The versatility of the oligomerization of propylene is very much evident from the extensive applications the individual products and their mixtures find. The oligomerization of ethylene essentially involves the addition of a C-H bond of one olefin molecule across the double bond of a second one. On the other hand, in the oligomerization of propylene four products are possible if only the vinylic C-H bonds are considered, two products involving a C-H bond of methylene carbon and another two involving a C-H bond of the methine carbon. The major products of the initial step of the oligomerization reaction are n-hexenes, 4-methyl-pentene, 2-methylpentene, and 2,3-dimethylbutene. The selectivity of the products depends on the metal, the ligands, and the mode of activation of the olefin. 

Particular studies of the IR spectra of homopolymers include isotactic poly(l-pentane), poly(4-methyl-l-pentene), and atactic poly(4-methyl-pentene) [16], chlorinated polyethylene (PE) [17], aromatic polymers including styrene, terephthalic acid, isophthalic acid [18], polystyrene (PS) [19-21], trans 1,4-polybutadiene [22], polyether-carbonate-silica nanocomposites [23], polyhydroxyalkanoates [24], poly(4-vinyl-n-butyl) [25], polyacetylenes [26], polyester urethanes [27], miscellaneous... 

Poly (4-methyl-1 -pentene) carbon dioxide and n-pentane 2006FA1... 

Note SAN styrene/acrylonitril copolymer CR-39 diethylene glycole bisallyl carbonate TPX poly-4-methyl-pentene-1. 

The following points may be noted. First, in 7.5 and 7.7 other /3-carbons are also available and eliminations from those will produce isomers of alkenes, which are not shown. Second, 7.1 can catalyze the isomerization of the products into the other isomers of -hexenes, methyl pentenes, and dimethyl butenes by the chain walk type of mechanism discussed earlier. 

Together these two products contain all eight carbons of the starting alkene The two carbonyl carbons correspond to those that were doubly bonded m the original alkene One of the doubly bonded carbons therefore bears two methyl substituents the other bears a hydrogen and a tert butyl group The alkene is identified as 2 4 4 trimethyl 2 pentene (CH3)2C=CHC(CH3)3 as shown m Figure 6 15... 

Methyl-l-Pen ten e. This olefin is produced commercially by dimeriza tion of propylene in the presence of potassium-based catalysts at 150—160°C and - 10 MPa. Commercial processes utilize several catalysts, such as sodium-promoted potassium carbonate and sodium- and alurninum-promoted potassium hydroxide (12—14) in a fixed-bed reactor. The reaction produces a mixture of C olefins containing 80—85% of 4-methyl- 1-pentene. 

Temperature control during pressure hydrogenation of cis- or tram-isomers is essential, since at 155°C violent decomposition to carbon, hydrogen and carbon monoxide with development of over 1 kbar pressure will occur. The material should not be heated above 100°C, particularly if acid or base is present, to avoid exothermic polymerisation [1], The m-isomer is readily cyclised to 2,3-dimethylfuran, which promotes lire and explosion hazards. These were measured for the cis- and tram-isomers, and for fram-3-methyl-l-penten-4-yn-3-ol [2],... 

Information published from several sources about 1970 presented details on both the halide-containing RhCl(CO)(PPh3)2- and the hydride-containing HRh(CO)(PPh3)3-catalyzed reactions. Brown and Wilkinson (25) reported the relative rates of gas uptake for a number of different olefinic substrates, including both a- and internal olefins. These relative rates are listed in Table XV. 1-Alkenes and nonconjugated dienes such as 1,5-hexadiene reacted rapidly, whereas internal olefins such as 2-pentene or 2-heptene reacted more slowly by a factor of about 25. It should also be noted that substitution on the 2 carbon of 1-alkene (2-methyl-l-pentene) drastically lowered the rate of reaction. Steric considerations are very important in phosphine-modified rhodium catalysis. 

The longest carbon chain containing the double bond is 5 carbons long. The double bond is between carbons 1 and 2. There is a propyl group on carbon 2, and carbons 3 and 4 each have one methyl group. This is 3,4-dimethyl-2-propyl-l-pentene. 

The chiral sites which are able to rationalize the isospecific polymerization of 1-alkenes are also able, in the framework of the mechanism of the chiral orientation of the growing polymer chain, to account for the stereoselective behavior observed for chiral alkenes in the presence of isospecific heterogeneous catalysts.104 In particular, the model proved able to explain the experimental results relative to the first insertion of a chiral alkene into an initial Ti-methyl bond,105 that is, the absence of discrimination between si and re monomer enantiofaces and the presence of diastereoselectivity [preference for S(R) enantiomer upon si (re) insertion]. Upon si (re) coordination of the two enantiomers of 3-methyl-l-pentene to the octahedral model site, it was calculated that low-energy minima only occur when the conformation relative to the single C-C bond adjacent to the double bond, referred to the hydrogen atom bonded to the tertiary carbon atom, is nearly anticlinal minus, A- (anticlinal plus, A+). Thus one can postulate the reactivity only of the A- conformations upon si coordination and of the A+ conformations upon re coordination (Figure 1.16). In other words, upon si coordination, only the synperiplanar methyl conformation would be accessible to the S enantiomer and only the (less populated) synperiplanar ethyl conformation to the R enantiomer this would favor the si attack of the S enantiomer with respect to the same attack of the R enantiomer, independent of the chirality of the catalytic site. This result is in agreement with a previous hypothesis of Zambelli and co-workers based only on the experimental reactivity ratios of the different faces of C-3-branched 1-alkenes.105... 

The final stereochemistry of a metathesis reaction is controlled by the thermodynamics, as the reaction will continue as long as the catalyst is active and eventually equilibrium will be reached. For 1,2-substituted alkenes this means that there is a preference for the trans isomer the thermodynamic equilibrium at room temperature for cis and trans 2-butene leads to a ratio 1 3. For an RCM reaction in which small rings are made, clearly the result will be a cis product, but for cross metathesis, RCM for large rings, ROMP and ADMET both cis and trans double bonds can be made. The stereochemistry of the initially formed product is determined by the permanent ligands on the metal catalyst and the interactions between the substituents at the three carbon atoms in the metallacyclic intermediate. Cis reactants tend to produce more cis products and trans reactants tend to give relatively more trans products this is especially pronounced when one bulky substituent is present as in cis and trans 4-methyl-2-pentene [35], Since the transition states will resemble the metallacyclobutane intermediates we can use the interactions in the latter to explain these results. 

The most satisfactory species fulfilling these requirements is a half-hydrogenated radical. This is linked to the surface preferably through the tertiary carbon atom (which has the lowest C—H bond energy). The loss of a second hydrogen atom from its vicinity may lead to 3-methyl-2-pentene... 

The fact that about five times as much of 2,3,4,4-tetramethyl-l-pentene (XXXVIII) was obtained as its 2-isomer (XXXIX) indicates that the loss of a proton from either of the two methyl groups takes place about five times as easily as do the loss of the proton on the tertiary carbon atom that is part of the neopentyl system. Similarly, the relative amounts of 3,5,5-trimethyl-2-hexene and its 3-isomer (XL and XLI) indicates that the loss of a proton from the ethyl group occurs about five times as readily as from the neopentyl group no loss of a proton from the methyl group appears to have occurred. By analogy with the formation of the two isomeric diisobutylenes from the ear-bonium ion VI it would be expected that the carbonium ion XLII which leads to the formation of 2,4,4-trimethyl-2-hexene (XLIII) would yield the 1-isomer in about four to five times the amount of the 2-isomer. The failure to find any of the 1-isomer was little less than startling (Whitmore and Mixon, 47). 

Figure 13.6 is the proton-decoupled carbon-13 NMR distortionless enhancement of polarization transfer (DEPT) spectra of poly(methyl-l-pentene) [29]. This experiment, after data manipulation, separates the methine, methylene, and... 

Some representative examples of the [3+2] annulation are listed in Table I. Both cyclic and acyclic allenophiles participate in the reaction, a-Alkylidene ketones undergo annulation to provide access to spiro-fused systems, and acetylenic allenophiles react to form cyclopentadiene derivatives. The reactions of (E)- and (2)-3-methyl-3-penten-2-one illustrate the stereochemical course of the annulation, which proceeds with a strong preference for the suprafacial addition of the allene to the two-carbon allenophile. The high stereoselectivity displayed by the reaction permits the stereocontrol led synthesis of a variety of mono- and polycyclic systems. 

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