Alkenes lower

Production of specific higher and lower alkenes Diproportionation... 

Calculated Equilibrium Distributions for the Metathesis of Some Lower Alkenes at 898.16 Ka... 

Of course, even in the case of acyclic alkenes reaction enthalpy is not exactly zero, and therefore the product distribution is never completely statistically determined. Table V gives equilibrium data for the metathesis of some lower alkenes, where deviations of the reaction enthalpy from zero are relatively large. In this table the ratio of the contributions of the reaction enthalpy and the reaction entropy to the free enthalpy of the reaction, expressed as AHr/TASr, is given together with the equilibrium distribution. It can be seen that for the metathesis of the lower linear alkenes the equilibrium distribution is determined predominantly by the reaction entropy, whereas in the case of the lower branched alkenes the reaction enthalpy dominates. If the reaction enthalpy deviates substantially from zero, the influence of the temperature on the equilibrium distribution will be considerable, since the high temperature limit will always be a 2 1 1 distribution. Typical examples of the influence of the temperature are given in Tables VI and VII. 

In the hydroformylation of lower alkenes using a modified cobalt catalyst complex separation is achieved by distillation. The ligands are high-boiling so that they remain with the heavy ends when these are removed from the alcohol product. Distillation is not possible when higher alcohols or aldehydes are produced, because of decomposition of the catalyst ligands at the higher temperatures required. Rhodium complexes can usually also be removed by distillation, since these complexes are relatively stable. 

An important feature of biphasic hydroformylation is the separability due to density differences. Because of the differences in density of the polar compound water (1.0 gem"1) and the hydrophobic oxo products (average 0.8), no problems occur. Additionally, the hydroformylation products are not sensitive to water. Another important question is to what extent water and the reactants are mixed. Therefore, the reactor in Figure 5.3 b), a continuously stirred tank reactor (CSTR) [22], normally contains usual installations to guarantee excellent mixing. For the lower alkenes with their significant water solubility (propene, butene) this is no problem. In these cases, the hydroformylation reaction takes place at the interfacial region [23]. 

The lower alkenes and the heavy alkenes must be "disproportionated" to give the full range of alkenes. In the second part of the process the higher and... 

The promotion effects of Mn on unsupported Fe-based F-T catalysts were also studied by Jensen and Massoth. " These authors concluded that the incorporation of Mn chemically and electronically promotes the active Fe surface. More particularly, it appears to alter the CO hydrogenation reaction path by suppressing the direct formation of paraffins from the reactive intermediate, leading to the increased production of higher olefins. Finally, Das et al. also observed that the addition of moderated amounts of Mn promoter to unsupported Fe F-T catalysts promotes the catalytic activity as well as the selectivity towards lower alkenes. ... 

The reaction of adamantane with lower alkenes (ethylene, propylene, and butylenes) in the presence of superacids [CF3SO3H or CF3SO3H—B(0S02CF3)3] shows the involvement of both alkylations.34 In the predominant reaction the 1-adamantyl cation formed through protolytic C—H bond ionization of adamantane adamanty-... 

The reaction of aromatic compounds with alkenes giving alkylaromatic compounds has obtained more attention. A typical transformation is the alkylation of benzene by lower alkenes, e.g. 

Superacid-catalyzed alkylation of adamantane with lower alkenes (ethene, propene, isomeric butenes) has been investigated by Olah et al.151 in triflic acid and triflic acid-B(0S02CF3)3. Only trace amounts of 1 -ferf-butyladamantane (37) were detected in alkylation with 1- and 2-butenes, whereas isobutylene gave consistently relatively good yield of 37. Since isomerization of isomeric 1-butyladamantane under identical conditions did not give even traces of 37, its formation can be accounted for by (r-alkylation, that is, through the insertion of the ferf-butyl cation into the C—H bond (Scheme 5.22). This reaction is similar to that between ferf-butyl cation and isobutane to form 2,2,3,3-tetramethylbutane discussed above (Scheme 5.21). In either case, the pentacoordinate carbocation intermedate, which may also lead to hydride transfer, does not attain a linear geometry, despite the unfavorable steric interactions. 

The property of the polymers in question to form nonspherical nanostructures was confirmed in experimental studies. Shih et al. [29] synthesized alternating copolymers of 1-alkenes with maleic anhydride. The maleic anhydride units were hydrolyzed to maleic acid units. Fully hydrolyzed macromolecules associated into microstructures of cylindrical and ellipselike shape. The cylindrical shape was characteristic of copolymers with octadecene and hexadecene moieties, while the copolymers with lower alkene copolymers (tetradecene, dodecene, decene, octene) formed ellipsoidal structures. Wataoka et al. [30] investigated the formation of nonspherical helices in a system of maltopentaose-carrying polystyrene (PS). The polymer was synthesized via the homopolymerization of vinylbenzyl maltopentaose amide (Scheme 3). 

A system that has received considerable interest in recent years is the catalytic conversion of methanol to gasoline. Numerous hypotheses have been advanced to explain the mechanism, and solid-state 13 C n.m.r. has played an important role in this respect, in that it can directly examine the organic species in the zeolite without any interference from the inorganic matrix. The initial formation of dimethyl ether from methanol over H-ZSM-5 was proposed by van Hooff 141 subsequent dehydration and methylation reactions lead to lower alkenes,142 which in turn oligomerize at ambient temperature to linear alkyl chains.143 At temperatures of about 373 K, branched alkyl chains are also formed. Many more promising applications can be anticipated in this area. 

It has been suggested that alkene or alkyne complexes are mechanistically important intermediates in hydroalumination and carboalumination reactions (124-126). Clear spectroscopic evidence for n interactions stems from investigations of alkenylaluminum compounds having a suitable intramolecular separation between the aluminum center and the double bond (127). IR and NMR data of these compounds show comparably lower alkene stretching frequencies and deshielded vinylic protons. Furthermore, these molecules are monomeric in solution this indicates that the tendency toward 7i-complex formation is stronger than that toward the dimeric bonding usual in aluminum alkyls. 

Diphenyl carbonate from dimethyl carbonate and phenol Dibutyl phthalate from butanol and phthalic acid Ethyl acetate from ethanol and butyl acetate Recovery of acetic acid and methanol from methyl acetate by-product of vinyl acetate production Nylon 6,6 prepolymer from adipic acid and hexamethylenediamine MTBE from isobutene and methanol TAME from pentenes and methanol Separation of close boiling 3- and 4-picoline by complexation with organic acids Separation of close-boiling meta and para xylenes by formation of tert-butyl meta-xyxlene Cumene from propylene and benzene General process for the alkylation of aromatics with olefins Production of specific higher and lower alkenes from butenes... 

Early investigations on the oxidative addition of halogens to alkenes have mainly been focused on the preparation of epoxides from lower alkenes such as ediylene and propene. ... 

The production of carbonyl compounds and lower alkenes in pairs may be accounted for qualitatively in this way [77]. C-tracer studies [113,114] leave little doubt that these reactions occur to an appreciable extent. Even so they have received little attention from the thermokinetic point of view. The likely order of magnitude of 1 may be assessed, however, from consideration of the strengths of the bonds broken and of those formed. Thus, for the decomposition of the 2-hydroperoxy-3-ethylpent-4-yl radical... 

It was pointed out in Sect. 3.2.2(a)(iv) that on the basis of, 6-scission decompositions of hydroperoxyalkyl radicals equal yields of lower carbonyl compounds and their corresponding lower alkene would be expected, but that this is not found in experiment where the yield of the... 

As emphasized earlier, alkenes are major primary products with 50-99% yields of conjugate alkene in the oxidation of C2—alkanes between 600 and 800 K. Increasing amounts of lower alkenes are formed above 800 K, as homolysis competes favourably with oxidation. 

As a final comment here, it is pertinent to point out that the problem over lower alkene formation arises solely with CaHg and isobutene which are the only alkenes to give stable electron delocalized radicals, allyl and methylallyl, which do not have a facile reaction with O2 and are consumed (at least in the range 600-1000 K) mainly through radical-radical processes. Together with the mutual reactions of the two species, their reactions with HO2 will be the major processes involved. It is conceivable that C2H4 is formed in one of the reaction channels from the CH2CHCH2 + HO2 reaction. 

Alkylation is a synthetic process in which lower alkenes (from catalytic cracking) are reacted in an acid medium (sulphuric or hydrofluoric acid) with small branched alkanes to produce Cg to Cg branched alkanes. These are probably the most desirable constituents of a gasoline, with good knock resistance and with fewer undesirable properties, such as tendencies to... 

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