Ethene, atmosphere

The organotitanium compounds produced by desulfurization of the diphenyl thioacetals of aldehydes 28 with the titanocene(II) species Cp2Ti[P(OEt)3]2 29 react with carbon—carbon double bonds to form the olefin metathesis-type products. Thioacetals 28 may be transformed into terminal olefins by desulfurization with 29 under an ethene atmosphere (Scheme 14.15) [27]. This reaction is believed to proceed through a titanacyclobutane intermediate, formed by cycloaddition of the titanocene-alkylidene with ethene. 

Bicyclic dienic products recently synthesized by this method (Scheme 36) are lactams 144a and b (07T8267) and enamine ester 145 (09CEJ4565). The precursor of the latter substance originates from a four-component synthesis followed by y-allylation. The alternative y-propargylation and subsequent ring-closing enyne metathesis performed under an ethene atmosphere lead to the 8-vinyl derivative of product 145. 

The complex [Re(CO)5(j/2-C2H4)][BF4] may also be obtained directly from the reaction of [Ph3C][BF4] with Re(CO)5(CH3) in an ethene atmosphere. Reaction time 3-4 days. Yield (95-98%). 

Dmphen)(ethene)platinum can be stored in ethene atmosphere at — 20°C without appreciable decomposition for several weeks. It is soluble in chloroform, which reacts with the complex within a few seconds, affording the five-coordinate product [PtCl(CHCl2)(dmphen)(ethene)].14 Methylene... 

The parent zirconacyclopentane 27a can be synthesised by either the reaction of Cp2ZrCl2 with BrMg(CH2)4MgBr as reported by Takahashi and co-workers or by warming dibutylzirconocene (Cp2ZrBu2) to room temperature under an ethene atmosphere 32... 

Solutions of the complexes are stable for several hours at room temperature under an ethene atmosphere. Decomposition takes place if the compound is heated (> 65°). If the solvent is removed under reduced pressure, a red-brown oil of uncertain composition is formed. 

The reactions of the dinuclear complex [Cp 2Rti2(li H)4l with ethene affoideactivated product [Cp 2Ru2(CH2=CH2)(CH=CH2)2]. which underwent tlwrmolysis under an ethene atmosphere to afford the C-C coupled product [Cp 2Ru2(CH2=CH2)(CMe=CHCH=CMe)]. 

Even more important is the stereoregular catalytic polymerization of ethene and other alkenes to give high-density polyethene ( polythene ) and other plastics. A typical Ziegler-Natta catalyst can be made by mixing TiCU and Al2Eti in heptane partial reduction to Ti " and alkyl transfer occur, and a brown suspension forms which rapidly absorbs and polymerizes ethene even at room temperature and atmospheric pressure. Typical industrial conditions are 50- 150°C and 10 atm. Polyethene... 

Ethene and propene are produced as bulk feedstocks for the chemical (polymer) industry and therefore their purities are important parameters. In particular, H2S and COS are compounds which may not only cause corrosion problems in processing equipment, but also may have detrimental effects on the catalysts in use. Eurthermore, air pollution regulations issued by, among others, the US Environmental Protection Agency (EPA) require that most of the sulfur gases should be removed in order to minimize Sulfur emissions into the atmosphere. Therefore, these compounds have to be determined to the ppb level. 

Solid catalysts for the metathesis reaction are mainly transition metal oxides, carbonyls, or sulfides deposited on high surface area supports (oxides and phosphates). After activation, a wide variety of solid catalysts is effective, for the metathesis of alkenes. Table I (1, 34 38) gives a survey of the more efficient catalysts which have been reported to convert propene into ethene and linear butenes. The most active ones contain rhenium, molybdenum, or tungsten. An outstanding catalyst is rhenium oxide on alumina, which is active under very mild conditions, viz. room temperature and atmospheric pressure, yielding exclusively the primary metathesis products. 

Fig. 8 Dependence of catalytic activity measured by TOP (rate of reaction per Rh atom) (squares) and IR intensity of hydride (2020-cm mode) (diamonds) during the induction period for ethene hydrogenation catalyzed by Rhg supported on La203 at 298 K and atmospheric pressure in a flow reactor (partial pressures in feed H2, 348 Torr C2H4, 75Torr He, 337 Torr) [37]...

Of the alkenes (Figure 5.5) only ethene has been detected and of the aromatics only benzene has been seen unambiguously surprisingly propene has not been seen despite its well-understood microwave spectrum. Of interest to the origins of life is the onset of polymerisation in HCN to produce cyanopolyynes. These molecules could provide a backbone for the formation of information-propagating molecules required for self-replication. The survival of these species in a planetary atmosphere depends on the planet oxidation would be rapid in the atmosphere of today s Earth but what of the early Earth or somewhere altogether more alkane-based such as Titan ... 

Much ethanol is manufactured by the hydration of ethene. The reaction is an addition reaction between steam and ethene at 300 °C, in the presence of a solid phosphoric acid catalyst, at a pressure of about 70 atmospheres. 

For low-density poly(ethene), a high pressure (over 1500 atmospheres), a temperature of 200 °C and a trace of oxygen as a catalyst are needed. 

For high-density poly(ethene), a pressure of 2 to 6 atmospheres, a temperature of 60 °C and a catalyst of titanium (IV) chloride and triethyl aluminium are needed. 

Performing the cross-metathesis reactions at reflux (open to an argon atmosphere in a glove box) was designed to help remove the unwanted ethene produced by the reaction. 

The reactions were performed under a steady stream of nitrogen to aid the removal of ethene from the reaction mixture. Changing from a static nitrogen atmosphere to this flow of nitrogen resulted in a 30% yield enhancement and appeared to extend the life of the catalyst. 

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