High purity isoprene

Since most of the C, hydrocarbons boil extremely close to isoprene, simple distillation of the C, cut would not produce high purity isoprene. Two stages of extractive distillation with acetonitrile are used where the ACN modifies the relative volatilities of the hydrocarbons and thus enables the separation to be made. 

Takagi, K, Single-step synthesis of isoprene , Petroleum and Paroehm. internal, 12 (11) 62-66 (1972) Heath, K, High-purity isoprene fitnn acetone acetylene", Chem Engng, 80 (22) 48-49 (1973)... 

Dehydrogenation of Tertiary Amylenes, The staiting material here is a fiaction which is cut from catal57tic clacking of petroleum. Two of the tertiary amylene isomers, 2-methyl-l-butene and 2-methyl-2-butene, are recovered in high purity by formation of methyl tertiary butyl ether and cracking of this to produce primarily 2-methyl-2-butene. The amylenes are mixed with steam and dehydrogenated over a catalyst. The cmde isoprene can be purified by conventional or extractive distillation. 

Materials. 5-Methyl-1,4-hexadiene was obtained by the codimerization of isoprene and ethylene with a catalyst (18) consisting of iron octanoate, triethylaluminum and 2,2 -bi-pyridyl. The product mixture which contained principally 5-methyl-1,4-hexadiene and 4-methy1-1,4-hexadiene was fractionated through a Podbielniack column to yield high purity (>99%) 5-methylxhexadiene, b.p. 92.80C,njj 1.4250 (Lit. (19) b.p. 88-89°C, np 1.4249). 1-Hexene (99.9% purity), 1-decene (99.6% purity), 4-methyl-1-hexene (99.5% purity) and 5-methyl-l-hexene (99.7% purity) were obtained from Chemical Samples Co. 6-TiCl3 AA (Stauffer Chemical Co.j contains 0.33 mole AICI3 per mole of TiClj). Diethylaluminum Chloride was obtained from Texas Alkyls (1.5 M in hexane). 

Polymerization of isoprene can yield high-purity cis-l,4-polyisoprene and trans-l,4-polyisoprene. Isoprene is 2-methyl-1,3-butadiene, 2-methyldivinyl, or 2-methylerythrene. Isoprene is polymerized by 1,4 or vinyl addition, the former producing cis-1,4 or trans-1,4 isomer. ... 

Polymerization of isoprene can yield high purity ci5 -l,2-polyisoprene and trans-1,4-polyisoprene. Depolymerized polyisoprene liquid is used as a reactive plasticizer for adhesive tapes, hot melts, brake linings, and wire and cable sealants. 

Organoaluminum compounds are used as polymerization catalysts of butene, isoprene and butadiene besides ethylene and propylene, dimerization catalysts of linear higher a-olefins, linear higher-a-alcohols and olefins, productions of organo-metallic compounds such as organotin compounds and organolead compounds, productions of high purity alumina and aluminum thin film. 

Method of synthesis cationic polymerization of high purity Isobutylene and isoprene is used to produce butyl rubber in the presence of complex systems of catalysts polymerization is terminated by irreversible destruction of the propagating carbenium ion by the collapse of the ion pair, by hydrogen abstraction from the comonomer, by formation of stable allylic carbenium ions, or by reaction with nucleophilic species such as alcohols or amines ... 

A liquid synthetic polyisoprene is marketed by the Japanese company Kuraray. This product, which is made by the polymerization of isoprene monomer, is available in a wide range of different viscosity and chemically modified grades. Because of its high purity, there is a significant market in surgical adhesives. 

The potentially useful synthetic isoprene unit , 3-methylbut-2-enylmagnesium chloride (31), reacts with various epoxides to give the product (32) in high yield (80%) and high purity (>98%). In the presence of 10% cuprous iodide, however, the reaction takes a different course to give the product (33) in equally... 

Table 3 provides typical specifications for isoprene that are suitable for Al—Ti polymerization (89). Traditional purification techniques including superfractionation and extractive distillation are used to provide an isoprene that is practically free of catalyst poisons. Acetylenes and 1,3-cyclopentadiene are the most difficult to remove, and distillation can be supplemented with chemical removal or partial hydrogenation. Generally speaking distillation is the preferred approach. Purity is not the main consideration because high quaUty polymer can be produced from monomer with relatively high levels of olefins and / -pentane. On the other hand, there must be less than 1 ppm of 1,3-cyclopentadiene. 

Monomers for manufacture of butyl mbber are 2-methylpropene [115-11-7] (isobutylene) and 2-methyl-l.3-butadiene [78-79-5] (isoprene) (see Olefins). Polybutenes are copolymers of isobutylene and / -butenes from mixed-C olefin-containing streams. For the production of high mol wt butyl mbber, isobutylene must be of >99.5 wt % purity, and isoprene of >98 wt % purity is used. Water and oxygenated organic compounds iaterfere with the cationic polymerization mechanism, and are minimized by feed purification systems. 

Another issue important to the success of this chiral titanium reagent 31 was the discovery of a marked solvent effect. When the fumaric acid derivative is reacted with isoprene in the presence of 10 mol% of the titanium reagent 31 in toluene, poor optical purity results (36-68% ee). Interestingly the optical purity of the adduct greatly increased in the order benzene, toluene, xylenes, and mesitylene, with 92% ee obtained in the last. Mesitylene is difficult to remove, because of its high boiling point, and other solvents were screened in detail. As a result, the mixed solvent system toluene petroleum ether (1 1) was discovered to be very effective. 

The Diels-Alder reaction catalyzed by this chiral titanium catalyst 31 has wide generality (Scheme 1.53, 1.54, Table 1.22, 1.23). Acryloyl- and fumaroyl-oxazolidinones react with isoprene giving cycloadducts in high optical purity. 2-Ethylthio-l,3-buta-diene can also be successfully employed as the diene [42]. 

Similarly a marked increase of regioselectivity has been shown in the catalyzed Diels-Alder reactions of the chiral bicyclic lactame 24 (Scheme 3.9) with a variety of dienes [27] (isoprene, mircene, (E,E)-L4-dimethylbutadiene, 2,3-di-methylbutadiene, 2-siloxybutadiene). The catalyzed reactions were more regio-selective and totally enJo-antz-diastereoselective anti with respect to the bridgehead methyl group). The results of the cycloadditions with isoprene and mircene are reported in Scheme 3.9. The cycloadducts have then been used to provide interesting fused carbocycles [28] with high enantiomeric purity as shown in Scheme 3.10. 

Figure 19.7. Cyclic batch elution chromatography obtaining high product purity and high throughput by using incomplete resolution (overlapping bands) and recycling the mixed fraction (mf) to the feedstock (a) Control of band separation and cut points determines fractional impurities t mij mr and Ami /mr2-<4l)> (b) Chromatogram for separation of pure ds- and trans- 1,3-pentadiene. Components 1, isoprene 2, trans- 1,3-pentadiene 3, cis-l,3-pentadiene 4, cyclo-pentadiene. Component 1 is eluted at almost the same time as component 4 of the...

Kraton synthetic isoprene rubbers are offered as an alternative to natural rubber products, and provide an option for use in applications requiring no discolouration, odour and a high degree of purity. The benefits are described of two currently available synthetic isoprene processing technologies, - Kraton anionically polymerised IR marketed by Shell and Ziegler-Natta IR, with reference to their ability to reduce problems of discolouration, odour and adverse skin reactions, and to improve the overall quality and performance of finished products without sacrificing the traditional benefits of NR. 2 refs. 

Ceresa drew attention to the fact that out of 1400 copolymers only 5% of the products had been isolated with a reasonable degree of purity and only 20 species had been properly characterized. Exploitation of anionic polymerization, however, soon improved the situation markedly. The use of alkyllithium initiators, which were initially evaluated by Stavely and co-workers at Firestone for the synthesis of high-cis polyisoprene, in the preparation of block copolymers from styrene and butadiene, and styrene and isoprene, is particularly noteworthy. 

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