A-Olefin mixtures

FIG. 2 Molecular weight distribution in the homologous a-olefin mixtures of the single-step and two-step Alfen process, x —x, Single-step reaction O—O, two-step reaction. 

Afterward the new aluminum alkyl is transalkylated with a C,2-Cl8 n-a-olefin mixture ... 

Use of less sterically hindered examples of 5 in combination with MAO allows for active catalysts for the linear (head-to-head) dimerisation of a-olefins such as 1-butene, 1-hexene, 1-decene and Chevron Phillips C20-24 a-olefin mixture (Scheme 4) [47], The mechanism for dimerisation is thought to involve an initial 1,2-insertion into an iron-hydride bond followed by a 2,1-insertion of the second alkene and then chain transfer to give the dimers. Structurally related cobalt systems have also been shown to promote dimerisation albeit with lower activities [62], Oligomerisation of the a-olefms propene, 1-butene and 1-hexene has additionally been achieved with the CF3-containing iron and cobalt systems 5j and 6j yielding highly linear dimers [23],... 

Polyolefins with vinyl end groups can be readily transformed into end-functionalized polyolefins by post-polymerization functionalization to yield a wide variety of end-functionalized polyolefins, which include epoxy-, amine-, and hydroxy-terminated polyolefins. Brookhart, Gibson, and co-workers reported on diimine-pyridine-ligated Fe complexes incorporating sterically less hindered alkyl substituents such as a methyl group ortho to the imine-A s, F12-1, that selectively converted ethylene to oligomers, affording linear a-olefin mixtures (>99%) (see also Section... 

Fall, J., Mdczewska, K., and Voelkel, A. (2001) Characterization of mineral oil/ polyester, mineral oil/poly-a-olefin mixtures by inverse gas chromatography. 

The presumed 14 electron Ti(C5Me5)(2,4-C7Hn), Ti(Ph2CH)2, and Ti(Ph2C-SiMc3)2 complexes (Section IIIA), as well as a variety of other open and half-open titanocenes, have been reported to yield, upon activation with MAO and/or poorly coordinating borate ions, catalysts for the polymerization of ethylene/a-olefin mixtures, styrene, vinylcyclohexane, vinylcyclohexene, butadiene, and related spedes." The polystyrene was isolated predominately in the syndiotactic form. 

If alkyl groups are attached to the ylide carbon atom, cis-olefins are formed at low temperatures with stereoselectivity up to 98Vo. Sodium bis(trimethylsilyl)amide is a recommended base for this purpose. Electron withdrawing groups at the ylide carbon atom give rise to trans-stereoselectivity. If the carbon atom is connected with a polyene, mixtures of cis- and rrans-alkenes are formed. The trans-olefin is also stereoseiectively produced when phosphonate diester a-carbanions are used, because the elimination of a phosphate ester anion is slow (W.S. Wadsworth, 1977). 

Ziegler found that adding certain metals or their compounds to the reaction mixture led to the formation of ethylene oligomers with 6-18 carbons but others promoted the for matron of very long carbon chains giving polyethylene Both were major discoveries The 6-18 carbon ethylene oligomers constitute a class of industrial organic chemicals known as linear a olefins that are produced at a rate of 3 X 10 pounds/year m the... 

Shell Higher Olefin Process) plant (16,17). C -C alcohols are also produced by this process. Ethylene is first oligomerized to linear, even carbon—number alpha olefins using a nickel complex catalyst. After separation of portions of the a-olefins for sale, others, particularly C g and higher, are catalyticaHy isomerized to internal olefins, which are then disproportionated over a catalyst to a broad mixture of linear internal olefins. The desired fraction is... 

Chromium Oxide-Based Catalysts. Chromium oxide-based catalysts were originally developed by Phillips Petroleum Company for the manufacture of HDPE resins subsequendy, they have been modified for ethylene—a-olefin copolymerisation reactions (10). These catalysts use a mixed sihca—titania support containing from 2 to 20 wt % of Ti. After the deposition of chromium species onto the support, the catalyst is first oxidised by an oxygen—air mixture and then reduced at increased temperatures with carbon monoxide. The catalyst systems used for ethylene copolymerisation consist of sohd catalysts and co-catalysts, ie, triaLkylboron or trialkyl aluminum compounds. Ethylene—a-olefin copolymers produced with these catalysts have very broad molecular weight distributions, characterised by M.Jin the 12—35 and MER in the 80—200 range. 

Properties of other higher a-olefins and those of some commercially significant cycloolefins are given in Table 2. These monomers are fiquids at ambient temperature and pressure. They are highly combustible and can form explosive mixtures with air. The primary health hazards presented by these monomers are associated with inhalation or prolonged skin contact that can cause irritation. 

Idemitsu Process. Idemitsu built a 50 t x 10 per year plant at Chiba, Japan, which was commissioned in Febmary of 1989. In the Idemitsu process, ethylene is oligomerised at 120°C and 3.3 MPa (33 atm) for about one hour in the presence of a large amount of cyclohexane and a three-component catalyst. The cyclohexane comprises about 120% of the product olefin. The catalyst includes sirconium tetrachloride, an aluminum alkyl such as a mixture of ethylalurninumsesquichloride and triethyl aluminum, and a Lewis base such as thiophene or an alcohol such as methanol (qv). This catalyst combination appears to produce more polymer (- 2%) than catalysts used in other a-olefin processes. The catalyst content of the cmde product is about 0.1 wt %. The catalyst is killed by using weak ammonium hydroxide followed by a water wash. Ethylene and cyclohexane are recycled. Idemitsu s basic a-olefin process patent (9) indicates that linear a-olefin levels are as high as 96% at C g and close to 100% at and Cg. This is somewhat higher than those produced by other processes. 

Coal tar is the condensation product obtained by cooling to approximately ambient temperature, the gas evolved in the destmctive distillation of coal. It is a black viscous Hquid denser than water and composed primarily of a complex mixture of condensed ring aromatic hydrocarbons. It may contain phenoHc compounds, aromatic nitrogen bases and their alkyl derivatives, and paraffinic and olefinic hydrocarbons. Coal-tar pitch is the residue from the distillation of coal tar. It is a black soHd having a softening point of 30—180°C (86—359°F). 

Commercially, sulfonic acid ion-exchange resins are used in fixed-bed reactors to make these tertiary alkyl ethers (14). Since the reaction is very selective to tertiary olefins and also reversible, a two-step procedure is also used to recover commercially pure tertiary olefins from mixed olefin process streams. The corresponding tertiary alkyl ether is produced in the olefin mixture and then easily separated from the unreacted olefins by simple fractionation. The reaction is then reversed in a second step to make a commercially pure tertiary olefin, usually isobutylene or isoamylene. 

In the production of a-olefins, ethylene reacts with an aluminum alkyl at relatively low temperature to produce a higher aLkylalumiaum. This is then subjected to a displacement reaction with ethylene at high temperatures to yield a mixture of a-olefins and triethylalumiaum. In an alternative process, both reactions are combiaed at high temperatures and pressures where triethylalumiaum fuactioas as a catalyst ia the polymerization process. 

Evaporative emissions from vehicle fuel systems have been found to be a complex mixture of aliphatic, olefinic, and aromatic hydrocarbons [20,24,33]. However, the fuel vapor has been shown to consist primarily of five light paraffins with normal boiling points below 50 °C propane, isobutane, n-butane, isopentane, and n-pentane [33]. These five hydrocarbons represent the more volatile components of gasoline, and they constitute from 70 to 80 per cent mass of the total fuel vapor [24,33]. 

The product is predominantly the A -olefin, which is neither the more stable isomer (the equilibrated mixture is 2 1, A A ) nor the product expected from 1 elimination (this would be the A -olefin). It is noteworthy that this elimination was conducted in the absence of pyridine. 

While the dehydrohalogenation of 3-halo-5a-steroids gives the A -olefin selectively, it has been shown that in the 5j5-series dehydrochlorination of 3j5-chloro compounds with quinoline gives a mixture of A - and A -olefins in a 45 55 ratio. 

The pure olefin is best prepared via the bromohydrin (131) a more direct route from the tosylate (129) yields a mixture of (132) and its A -isomer. The indirect method is most suitable for preparing A -olefins in the 5jS-series. 

Optimum conditions for allylic alcohol formation ( 65% yield of olefin mixture) appear to be those originally described by Wharton, rather than strongly basic forcing conditions. The pyrazole (147) is a by-product. 

In some reactions intramolecular chalcogen nitrogen interactions may lead to stereochemical control. For example, selenenyl bromides react with C=C double bonds, providing a convenient method of introducing various functional groups. The reaction proceeds readily, but affords a racemic mixture. The modified reagent 15.22 contains a chiral amine in close interaction with the selenium atom. It reacts with olefins affording up to 97% ee of isomer A (Scheme 15.2). ... 

For the regioselectivity similar rules as for the ester pyrolysis do apply. With simple, alkylsubstituted amine oxides a statistical mixture of regioisomeric olefins is obtained. On the other hand with cycloalkyl amine oxides the regioselectivity is determined by the ability to pass through a planar, five-membered transition state. This has been demonstrated for the elimination reaction of menthyl dimethylamine oxide 10 and neomenthyl dimethylamine oxide 11 ... 

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