Ethylene/ethene reactions

Small olefins, notably ethylene (ethene), propene, and butene, form the building blocks of the petrochemical industry. These molecules originate among others from the FCC process, but they are also manufactured by the steam cracking of naphtha. A wealth of reactions is based on olefins. As examples, we discuss here the epoxida-tion of ethylene and the partial oxidation of propylene, as well as the polymerization of ethylene and propylene. 

In 1954, Ziegler and coworkers observed that the course of the reaction of ethene with trialkylalanes was drastically altered by the presence of traces of nickel salts [25]. Instead of low molecular weight polyethylene, the only product was 1-butene. Obviously, the transition metal strongly supports the displacement reaction of the alkyl group bonded to the aluminum by ethylene, a reaction which can be formally described as transfer of a hydridoalane. 

Perhaps the next simplest molecular adsorbates for which quantitative structural information exists are the unsaturated C2 hydrocarbons, notably acetylene (ethyne, HC CH) and ethylene (ethene, H2C=CH2), adsorbed on a number of metal surfaces (especially, Cu, Ni and Pd), and also on Si(100), studied by LEED, SEXAFS, and PhD. In some systems adsorption of ethylene is accompanied by a surface reaction. In particular, on both Pt(lll) [74] and Rh(lll) [75] ethylene is converted to an ethylidyne species, H3C—C—, which bonds to these surfaces through the C atom with the —C axis essentially perpendicular to the surface, in three-fold coordinated hollow sites. In addition, ethylene adsorbed on Ni(l 11) at low temperature dehydrogenates to produce adsorbed acetylene as the surface is warmed towards room temperature this particular system actually provided the first example of the... 

With the advent of sophisticated experimental techniques for studying surfaces, it is becoming apparent that the structure of chemisorbed species may be very different from our intuitive expectations.10 For example, ethylene (ethene, H2C=CH-2) chemisorbs on platinum, palladium, or rhodium as the ethylidyne radical, CH3—C= (Fig. 6.2). The carbon with no hydrogens is bound symmetrically to a triangle of three metal atoms of a close-packed layer [known as the (111) plane of the metal crystal] the three carbon-metal bonds form angles close to the tetrahedral value that is typical of aliphatic hydrocarbons. The missing H atom is chemisorbed separately. Further H atoms can be provided by chemisorption of H2, and facile reaction of the metal-bound C atom with three chemisorbed H atoms dif-... 

In 1897, Sabatier and Senderens ( ) made a pioneering study of the use of a nickel as a catalyst for the hydrogenation of ethylene (ethene) to ethane. This investigation led to the award of the Nobel Prize to Sabatier in 1912. Since that time the importance of heterogeneous catalysts has continued to increase greatly, decade by decade, extending the boundaries of laboratory chemical researches and promoting new and more cost-effective processes within the chemical industry (2). The correct choice of a catalyst allows a desired reaction to proceed under milder conditions of temperature and pressure than would be... 

Bromine (Br2) is brown, and one of the classic tests for alkenes is that they turn a brown aqueous solution of bromine colourless. Alkenes decolourize bromine water alkenes react with bromine. The product of the reaction is a dibromoalkane, and the reaction below shows what happens with the simplest alkene, ethylene (ethene). 

In 1864, ethylene was first expressed graphically in its modem form with a double bond connecting the two carbon atoms (CH2=CH2). This was adopted by Wanklyn to represent the constitutional formula of rosaniline (6), and made public in September of that year at the annual meeting of the British Association for the Advancement of Science, held in Bath. Wanklyn s ethylene-type formula showed two carbon atoms separated from the four hydrogen atoms by a bracket18. The ethylene type, unlike other type formulas, was used only to express the constitutions of coal-tar dyes. Wanklyn argued that the constitutions of the members of the rosaniline series could be expressed by his ethylene type by virtue of known reduction and replacement reactions. Thus he compared the conversion of 6 into colorless leucaniline (10) with the ready reduction of ethylene (ethene) (11) to ethane (12), both of which involved the addition of two hydrogen atoms (Scheme 4)19 21. 

The first step in the preparation of styrene involves the reaction between benzene (C6H6) and ethylene (ethene CH2=CH2), resulting in the formation of ethylbenzene (C6H5CH2CH3). The ethylbenzene is then dehydrogenated... 

When ethylene (ethene) is copolymerised with small proportions of higher alkenes (olefins), the resulting short-chain branches modify the polymer crystallinity (Section 3.4.1). Long-chain branched molecules (Fig. 2.8) can occur as a result of a side reaction for example when a propagating polyethylene molecule abstracts a H atom from a dead polyethylene molecule... 

Polyolefins belong to a group of thermoplastics polymerized through polyaddition reactions of olefins (unsaturated hydrocarbons). The most important polyolefins are ethylene (ethene), CH2=CH2, which gives polyethylene, and propylene (propene), CH2=CHCH3, which gives polypropylene when polymerized. 

Free radical polymerization, another example of a chain reaction (this chapter), is quite common and, for many alkenes and dienes, is the preferred method of polymer formation. Typically, as shown in Table 6.3 and Scheme 6.45, the initiator of the free radical process is a peroxide (such as di-fm-butylperoxide [(CH3)3C-0-0-C(CH3)3]). In Scheme 6.45a, the radical polymerization of ethylene (ethene, CH2=CH2) normally carried out at high pressure (>1(F atm) is shown, while as shown in Scheme 6.45b, the radical polymerization of a diene, 2-chloro-l, 3-butadiene [chloroprene, CH2=C(C1)CH=CH2], produces the all tram or (Z)-polymer called neoprene. ... 

Analysis of the three other 2 + 2 reactions in Table 6.5 (examples 3, 4, and 5) follows a similar course. Since the simplest reaction, the dimerization of ethylene (ethene [H2C=CH2]) with itself is thermally forbidden (A + A) and photochemi-cally allowed (,2s +, 2,) (Table 6.5, example 5) (Scheme 6.48a,b), it is reasonable to ask how the other examples might occur. Example 3, the cyclization of 1,1-dichloro-... 

For example, ethylene (ethene) can react with a free radical to form a stable O bond and a species which retains the free radical. This active site is capable of further reaction propagation of the polymerisation will continue until the active radical site is destroyed. Table 2.2 contains a list of a number of monomers and the corresponding vinyl based polymers. 

With primary or secondary amines, chlorosulfonic acid yields the corresponding sulfamic acid (Equation 5) this reaction with cyclohexylamine afforded the artificial sweetener sodium cyclamate 3 (Equation 9). In contrast to alkanes, alkenes readily react with chlorosulfonic acid to give the alkyl chlorosulfonates thus ethylene (ethene) is absorbed by chlorosulfonic acid to give ethyl chlorosul-fonate 4 (Equation 10). 

Monomers with carbon-to-carbon double bonds typically undergo chain-reaction pol3nnerization. The net result is that the double bonds open up and monomer units add to growing chains. As with other chain reactions, the mechanism involves three characteristic steps initiation, propagation, and termination. Let us illustrate this mechanism for the formation of the polymer polyethylene from the monomer ethylene (ethene). The key to the polymerization reaction is the free-radical initiator. In reaction (27.16), an organic peroxide dissociates into two radicals. The radicals add to the double bonds of ethylene molecules to form radical intermediates that attack more ethylene molecules and form new... 

CH2C1 CH2C1. Colourless liquid with an odour like that of chloroform b.p. 84 C. It is an excellent solvent for fats and waxes. Was first known as oil of Dutch chemists . Manufactured by the vapour- or liquid-phase reaction of ethene and chlorine in the presence of a catalyst. It reacts with anhydrous ethano-ales to give ethylene glycol diethanoate and with ammonia to give elhylenediamine, these reactions being employed for the manufacture of these chemicals. It burns only with difficulty and is not decomposed by boiling water. 

The much more stable MIL-lOO(Cr) lattice can also be impregnated with Pd(acac)2 via incipient wetness impregnation the loaded catalyst is active for the hydrogenation of styrene and the hydrogenation of acetylene and acetylene-ethene mixtures to ethane [58]. MIL-lOl(Cr) has been loaded with Pd using a complex multistep procedure involving an addition of ethylene diamine on the open Cr sites of the framework. The Pd-loaded MIL-lOl(Cr) is an active heterogeneous Heck catalyst for the reaction of acrylic acid with iodobenzene [73]. 

Norbornene-ethene copolymer, 16 113 Norbornene-ethylene copolymers, 20 433 physical properties of, 20 420-422 Norbornenodiazetine derivatives, 13 306 Nordel IP (metallocene), 7 637 Nordihydroguaiaretic acid, antioxidant useful in cosmetics, 7 830t Nordstrandite, 2 421, 425 activation, 2 394 classification, 2 422 decomposition sequence, 2 392 from gelatinous boehmite, 2 427 structural properties of, 2 423t NO-reduction reactions, TWC catalyst, 10 49... 

At 24 °C and 15-60 bar ethylene, [Rh(Me)(0H)(H20)Cn] catalyzed the slow polymerization of ethylene [4], Propylene, methyl acrylate and methyl methacrylate did not react. After 90 days under 60 bar CH2=CH2 (the pressure was held constant throughout) the product was low molecular weight polyethylene with Mw =5100 and a polydispersity index of 1.6. This is certainly not a practical catalyst for ethylene polymerization (TOP 1 in a day), nevertheless the formation and further reactions of the various intermediates can be followed conveniently which may provide ideas for further catalyst design. For example, during such investigations it was established, that only the monohydroxo-monoaqua complex was a catalyst for this reaction, both [Rh(Me)3Cn] and [Rh(Me)(H20)2Cn] were found completely ineffective. The lack of catalytic activity of [Rh(Me)3Cn] is understandable since there is no free coordination site for ethylene. Such a coordination site can be provided by water dissociation from [Rh(Me)(OH)(H20)Cn] and [Rh(Me)(H20)2Cn] and the rate of this exchange is probably the lowest step of the overall reaction.The hydroxy ligand facilitates the dissociation of H2O and this leads to a slow catalysis of ethene polymerization. 

So far, no reference has been made to the presence of more than one phase in the reactor. Many important chemicals are manufactured by processes in which gases react on the surface of solid catalysts. Examples include ammonia synthesis, the oxidation of sulphur dioxide to sulphur trioxide, the oxidation of naphthalene to phthalic anhydride and the manufacture of methanol from carbon monoxide and hydrogen. These reactions, and many others, are carried out in tubular reactors containing a fixed bed of catalyst which may be either a single deep bed or a number of parallel tubes packed with catalyst pellets. The latter arrangement is used, for exjimple, in the oxidation of ethene to oxiran (ethylene oxide)... 

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