Isomerisation reaction

The Combined System of Acid-Base Addition, (Z)/(E) and Prototropic Isomerisation Reactions of Arenediazonium Ions... 

Volume 1 Volume 2 Volume 3 The Practice of Kinetics The Theory of Kinetics The Formation and Decay of Excited Species Section 2. HOMOGENEOUS DECOMPOSITION AND ISOMERISATION REACTIONS... 

The gas-phase isomerisation reaction of cyclopropane to propylene satisfies the following rate expression ... 

Section 2. homogeneous decomposition and isomerisation reactions Volume 4 Decomposition of Inorganic and Organometallic Compounds Volume 5 Decomposition and Isomerisation of Organic Compounds... 

The aim of the present work was the investigation of the catalytic reactivity of different salts (K, NH4, Cs ) of H3PW12O40 and H4SiWi2O40 with various compositions in continuous liquid phase alkylation and its comparison with n-butane isomerisation reaction in gas phase. 

The most common isomerisation reactions catalysed by transition metals are those involving the isomerisation of alkenes. Taller, Crabtree and co-workers have reported that the iridium bfy-NHC complex 55 is effective for the isomerisation of... 

Isomerisation Reactions of Naturally Occurring Allenes. J. Chem. Soc. [London] 1956, 3767. 

C02 elimination and the substitution with water were the most exothermic degradation reactions and this confirmed the observation of C02 evolved during degradation. Isomerisation reactions were also investigated and assessed for the possible reaction pathway exothermicity. The calculations did not try and assess the transition states or barriers along the reaction pathways. 

Larcher, A. V., Alexander, R., Rowland, S. J. and Kagi, R. I. (1986) Acid catalysis of alkyl hydrogen exchange and configurational isomerisation reactions acyclic isoprenoid acids. Organic Geochemistry 10, 1015. 

An excess of ligand, including CO, will often inhibit isomerisation. HCo(CO)4, an unstable hydrido-carbonyl complex, belongs to the examples of catalysts also active in an atmosphere of CO. This is the only homogeneous catalyst being commercially applied, albeit primarily for its hydroformylation activity. Higher alkenes are available as their terminal isomers or as mixtures of internal isomers and the latter, the cheaper product, is mainly converted to aldehydes/alcohols by hydroformylation technology. Later we will see that the isomerisation reaction also plays a pivotal role in this system. Since 1990 several catalysts based on rhodium, platinum and palladium have been discovered that will also hydroformylate internal products to terminal aldehydes. 

Another application of an isomerisation reaction can be found in the production of the third monomer that is used in the production of EPDM rubber, an elastomeric polymerisation product of Ethene, Propene and a Diene using vanadium chloride catalysts. The starting diene is made from vinylnorbomene via an isomerisation reaction using a titanium catalyst. The titanium catalyst is made from tetravalent salts and main group hydride reagents, according to patent literature. 

Again we see that an alkene isomerisation reaction has taken place. Another important, useful reagent applied in this field is also pictured in Figure 15.7, viz. the use of benzoquinone as the re-oxidant for palladium. Quinone takes the role of dioxygen as oxidising agent. It is very efficient and both quinone and hydroquinone are inert towards many substrates. Furthermore, no water is formed, as is the case when dioxygen is used. 

Metathesis of 1-octene leads cleanly to ethene and 7-tetradecene, but as the reaction proceeds also 2-octene is formed and metathesis products derived from the isomerisation reaction. It was found that after prolonged reaction times decomposition of the ruthenium alkylidene catalyst occurs. At least eight different products were formed and several of them have been identified [37], Figure 16.22 shows the identified compounds derived from Grubbs 1st generation catalyst (the 2nd generation gives basically the same result [38]). 

Dextrose is widely used as an isotonic media in parenteral formulations. Sterilisation using autoclaving has been reported to induce the formation of fructose via an isomerisation reaction, with the resultant formation of 5-hydroxymethyl-furfural [90]. 

Section 2. HOMOGENEOUS DECOMPOSITION AND ISOMERISATION REACTIONS (2 volumes)... 

The catalytic performance of the supported bimetallic nano-particles in the hydrogenation of unsaturated molecules was tested on a wide variety of unsaturated species hex-l-ene, phenyl acetylene, diphenyl acetylene, trans-stilbene, cis-cyclooctene and D-limonene. The highly efficient hydrogenation of hex-1 -ene was accompanied by the isomerisation reaction to cis-and trans-hex-2-ene, which were subsequently hydrogenated (albeit at a much slower rate) as reaction ensued. 

From these results, it could be concluded that the external acidic sites are effectively involved in the isomerisation reaction, since the untreated zeolite is the most active. But, when these sites are thought to be totally poisoned, the reaction always takes place even if it is slowed down, so that the involvment of intracrystalline acidic sites must be taken into account. Nevertheless, the internal acidic sites can also be altered either by phenan-... 

There are rather few reactions that can be described as fully atom economical , i.e. when there are no co-products and all the atoms in the starting material(s) appear in the product(s). However, all isomerisation reactions necessarily fall into this category. The use of a transition metal to catalyse such a process with an appropriate substrate brings the possibility of effecting asymmetric isomerisation, a very efficient method to generate enantiomerically enriched products. Indeed, the asymmetric Rh-catalysed isomerisation of an allylamine to an enamine, which proceeds in over 96% ee, was scaled up a number of years ago for industrial production. The enamine product forms a multi-tonne feedstock for menthol and perfumery synthesis. In contrast, the cyclo-isomerisation of dienes, an equally atom-economical process that generates synthetically useful cyclic products, has seen relatively little development despite the reaction having been known for some 30 years. 

Compared with the previous example involving Rh-catalysed phenylation of cyclohexenone, the mechanistic investigation presented in this section involves a much less direct approach. This arises from the nature of the cyclo-isomerisation reaction, involving a single reactant and rather unstable intermediates. It is thus hard to manipulate the resting state of the catalytic cycle in order to facilitate direct study, e.g. by NMR, although Widenhoefer has... 

For example, let us consider the following reaction scheme for decom-position/isomerisation reactions... 

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