1-Hexene, from ethylene

Historically, McGuinness and Wasserscheid first reported on the preparation of bis (phosphino)amine chromium(III) chloride complexes, which, upon activation with MAO, act as highly selective catalysts for the production of 1-hexene from ethylene [156]. Bis(sulfanyl)amine-type ligands were subsequently found to be less expensive and easier to prepare [157]. These systems were then optimized by researchers at Sasol Technology and patented as selective catalysts for the formation of 1-hexene (>97%) using a low amount of MAO (30-100 equiv.) [158]. 

Oligomerization Dimerization or oligomerization of low molecular mass alkenes is regularly carried out industrially, with the aim of preparing linear 1-alkenes for synthetic use. In these applications, the presence of strong Lewis acids is undesirable, so neutral ionic liquids are used, exemplified by [bmim]PFg. ([bmim]+ is l-butyl-3-methylimidazolium.) This has been successful in the manufacture of hexenes from ethylene using a nickel complex as catalyst (Wasserscheid et al, 2001), with... 

Linear a-olefins were produced by wax cracking from about 1962 to about 1985, and were first commercially produced from ethylene in 1965. More recent developments have been the recovery of pentene and hexene from gasoline fractions (1994) and a revival of an older technology, the production of higher carbon-number olefins from fatty alcohols. 

Cr-based catalysts have been utilized for the synthesis of specific a-olefms, such as 1-hexene, and have been further developed by the use of ligands with novel structures. " Very recently, unprecedented selective tetramer-ization of ethylene was reported by Bollmann e/a/. to form 1-octene at >70% selectivity by using Gr(iii) precursors in conjunction with diphosphinamine ligands activated with MAO F12-10. Hessen and co-workers discovered that a hemilabile aryl group incorporated into the mono-Gp based Ti complexes F12-11 induced the unusual transformation of Ti complexes from ethylene-polymerization catalysts to selective trimerization catalysts. ... 

C are given in Table IV. The relatively greater proportion of 1-butene from ethylene-hexene copolymers indicates that there are two mechanisms for the formation of the butenes, one involving the butyl branches and that this pathway yields a much higher proportion (perhaps 100%) of 1-butene. The C4 hydrocarbons are apparently also formed by fragmentation of chain ends in the polymers. These are probably formed mainly by radiation-induced scission. 

The title olefins form complexes with Ni(0) with equilibrium constants for formation decreasing in the order ethylene > styrene > propylene 1-hexene > disubstituted alkenes (28). With ethylene and styrene the (olefin)NiL2 complexes have been isolated with L = P(0-o-tolyl)3. Addition of HCN to solutions of the pure olefin complexes results in rapid and complete conversion to alkylnickel cyanide intermediates which are spectroscopically detectable subsequent C—C coupling gives the observed nitrile products propionitrile from ethylene and (predominantly) 2-phenylpropion-itrile from styrene (47). The same alkyl intermediates are formed when ethylene and styrene are added to HNiL3CN [L = p(0-o-tolyl)3]. 

Reaction Mechanism. Any mechanism proposed for the vinylation of acetic acid by the hexenes must be able to account for the production of the high boiling products, 1,2-hexandiol mono- and diacetates (VIII, IX and X), and possibly hexylidene diacetate, as well as the hexenyl acetates. The currently accepted mechanism for synthesizing vinyl acetate from ethylene and acetic acid is derived from that postulated by Henry (i, 19), based on studies of the Wacker acetaldehyde synthesis. The key step in this mechanism is an insertion reaction (18). 

Formation of 1,1-diacetates—e,g., ethylidene diacetate from ethylene or hexylidene diacetate from hexene—by simple acetate displacement of palladium (Reaction 16) is a much more satisfactory reaction scheme than any previously proposed. On the other hand, accounting for 1,2-diol type products is diflBcult by this scheme, necessitating a reverse hydrogen transfer to form a two-carbon insertion product intermediate. This type... 

Ethylene for polymerization to the most widely used polymer can be made by the dehydration of ethanol from fermentation (12.1).6 The ethanol used need not be anhydrous. Dehydration of 20% aqueous ethanol over HZSM-5 zeolite gave 76-83% ethylene, 2% ethane, 6.6% propylene, 2% propane, 4% butenes, and 3% /3-butane.7 Presumably, the paraffins could be dehydrogenated catalyti-cally after separation from the olefins.8 Ethylene can be dimerized to 1-butene with a nickel catalyst.9 It can be trimerized to 1-hexene with a chromium catalyst with 95% selectivity at 70% conversion.10 Ethylene is often copolymerized with 1-hexene to produce linear low-density polyethylene. Brookhart and co-workers have developed iron, cobalt, nickel, and palladium dimine catalysts that produce similar branched polyethylene from ethylene alone.11 Mixed higher olefins can be made by reaction of ethylene with triethylaluminum or by the Shell higher olefins process, which employs a nickel phosphine catalyst. 

Addition of aliphatic hydrocarbons to ethylenic compounds occurs under the influence of catalysts such as sulfuric acid, phosphoric acid, and aluminum chloride.1 For instance, isobutane and propene afford the three isomeric heptanes. This reaction is not of particular importance in laboratory practice. However, addition of aromatic compounds to olefins is often a practicable method of alkylation.2 Thus ethylbenzene is formed from ethylene and benzene under the influence of aluminum chloride or when the hydrocarbon mixture is passed over a silica-alumina catalyst and Brochet3 obtained 2-phenyl-hexane from benzene and 1-hexene. The C-C bond is always formed to the doubly bonded carbon atom carrying the smaller number of hydrogen atoms benzene and propene, for instance, give cumene, which is important as intermediate in the preparation of phenol. Corson and Ipatieff4 report that benzene reacts especially readily with cyclohexene, yielding cyclohexylbenzene ... 

FIGURE 4.6 Expanded hydrogenated pyrograms of ethylene-propylene (EP), ethylene-1-butene (EB), ethylene-1-hexene (EHX), ethylene-l-heptene (EHP), and ethylene-l-octene (EO) reference copolymers and LDPE in the Cu region. 2M, 3M, 4M, 5M, 3E, 4E, and 5E are the same as those in Figure 4.5, and 4P is 4-propyloctane [12]. (From H. Ohtani et al.. Macromolecules 17 2558—2559 (1984). With permission.)... 

Recently, Choo and Way mouth performed the copolymerization of ethylene with 1,5-HD using various metallocene catalysts (12, 13, 14, Figure 19.2). 1,5-HD cyclopolymerized exclusively to give MCP units in the copolymers, with only traces of uncyclized 1,2-inserted 1,5-HD. The diaste-reoselectivity of the cyclocopolymerization favored the formation of 1,3-cyclopentane rings for metallocenes (74% trans for 12, 81% trans for 13, and 66% trans for 14). For metallocenes 12 and 14, the ethylene/1,5-HD copolymerization yielded copolymers with similar comonomer compositions and sequence distributions to those observed for ethylene/1-hexene copolymerization with these catalysts. On the other hand, the copolymers derived from metallocene 13 showed very different compositions and sequence distributions. At comparable comonomer feed ratios, the poly(ethylene-c -l,5-HD)s were enriched in the 1,5-HD comonomer and deficient in ethylene as compared to the analogous polymers prepared from ethylene and 1-hexene. The copolymerization behavior of 13 provided support for a dual-site alternating mechanism for 1,5-HD incorporation, wherein one coordination site of the active catalyst center is highly selective for the initial 1,2-inserion of 1,5-HD and the other site is selective for cyclization. 

Figure 10.7 Single branched fragments (Cjo) from ethylene-hexene-1 copolymer. Reproduced with permission from M. Seeger and E.H. Barrall,/oz/m/j/ of Polymer Science, Polymer Chemistry Edition, 1975,13, 7,1515. 1975, Wiley...

Fig. 4.35. A plot of the degree of crystallinity calculated from Raman internal modes, ac, against the mole percentage of branchpoints A hydrogenated poly butadiene ethylene-vinyl acetate ethylene-butene , ethylene-octene and f ethylene-hexene. From [206].

On February 28,1978, A. W. Anderson and G. S. Stamatoff received US. Patent 4,076,698. It was assigned to DuPont de Nemours and Company and provided DuPont the composition of matter on ethylene/1-olefin copolymers in which the 1-olefin contained 5 to 18 carbons. The original patent was filed on January 4, 1957. After a series of court proceedings that took place in the early 1980s, the court awarded DuPont the composition of matter claim on these copolymers. Hence, any polyethylene producer that offered ethylene/1-hexene or ethylene 1-octene copolymers from approximately 1978-1995 was obligated to pay DuPont a royalty. The copolymers produced by Anderson and coworkers were prepared with the solution... 

According to these experiments the polymerization of olefins is caused by a member (all members ) of the A species, while the B type centres cause some isomerization of the monomer. With catalysts of the same preparative history the specific polymerization activity is not dependent on the Cr concentration up to 1% [61, 62]. The reaction rate (as measured by the decrease of the monomer) is decreasing with tic from ethylene to 1-hexene [22],... 

X) was shown in Scheme 3.13. As previously reported in Ti (Blok et ah, 2003 de Bruin et ah, 2003, 2008 Tobisch and Ziegler, 2003, 2004a,b, 2005), Ta (Yu and Houk, 2003), and Cr (Bhaduri et ah, 2009 Budzelaar, 2009 Klemps et ah, 2009 Qi etak, 2010 vanRensburget ah, 2004) ethylene trimerization systems, the formation of 1-butene and 1-hexene from the metaUacyclopentane and metaUacycloheptane species, respectively, could foUow two different routes (1) one-step route that through a direct intramolecular-hydrogen transfer to the opposite a-carbon atoms (2) two-step route that via a Cr-H intermediate followed by reductive elimination. 

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