Unsaturated hydrocarbons oligomerization

C. Dynamic Aspects of Unsaturated Hydrocarbons Oligomerization and Polymerization on Metal-Containing Catalysts... 

Oligomeric polyperoxide is formed as a result of such copolymerization of the monomer and dioxygen. During oxidation of many unsaturated hydrocarbons, both reactions (abstraction and addition) occur in parallel to produce a mixture of hydroperoxides and oligomeric polyperoxides. The relative amounts of the products of R02 addition to the Tr-bond of olefins are given below [13] ... 

All unsaturated hydrocarbons that possess removable allylic hydrogens or activated double bonds readily undergo oligomerization in the presence of basic reagents.30,31 Alkali metals, organoalkali compounds, and alkali alcoholates are most frequently applied. 

The silyl fragmentation in superacids initiated by a controlled temperature increase is a method to generate persistent carbocations, such as the vinyl cation 378, which are not accessible by direct protonation of unsaturated hydrocarbons because of excessive formation of oligomeric and polymeric products. 

IV. Reactions Catalyzed by Bronsted Acid Sites The MTO Process and Oligomerization of Unsaturated Hydrocarbons... 

As part of the same comprehensive study Ziegler and Gellert also showed that at 180-200 °C complex (10) did catalyze the oligomerization of ethylene into higher ot-alkenes. Subsequently, the unstable AIH3 was found to add even more readily to ethylene and other a-alkenes (11) regioselectively to provide quantitative yields of the tri-n-alkylaluminum (12b). This reaction is thus the prototype for the hydroalumination of unsaturated hydrocarbons (equation 5). 

Secondary spectral features such as shake up satellites are frequently observed for polymeric materials containing unsaturated hydrocarbons. Theoretical studies have shown that these are associated with ti-ti transitions in aromatic materials. The shake up peak is clearly visible in the spectra of an oligomeric polyalkylthiophene that is being subjected to attack by and polystyrene (Figure 9.15). It should be noted that the difference between the binding energy for aliphatic carbons in the backbone of polystyrene and the... 

A number of reviews with relevant material address K-complexes of various kinds and iiKlude reviews on the syntheses of cationic 7t-complexes of the transition metals, die activation of C-C bonds in unsaturated hydrocarbons by metal complexes, a review on phosphorus heterocycles and phosphorus analogues of unsaturated hydrocarbon transition metal n-omiplexes J metal-complex catalyzed polymerizations of a-alkenes, coordination equilibria and coupling leactitms of unsaturated hydrocarbons at a metal centre, oligomerization of a-alkenes to higher oligomers, an annual survey on the chemistry of selected n-complexes for the year 1989, an annual survey on the chemistry of ferrocene for the year 1989, and in a number of articles in a journal issue devoted to alkene metathesis. 

As described above, nickel is liable to form Ti-coordination with unsaturated hydrocarbons as shown in Figures 19.3—19.6. By taking advantage of the readiness of these r-coordination formation reactions, oligomerizations such as dimerization and trimerization, cyclizations, polymerizations and coupling reactions of nickel compounds with unsaturated compounds are liable to proceed as shown in eqs. (19.36)-( 19.38). For example, the coupling reaction, coupling cyclization and intramolecular cyclization are shown in eqs. (19.46)-( 19.49). These reactions are considered to proceed via -coordination of unsaturated bonds such as double bonds, tripled bonds and allyl bonds [49,65, 86-91]. 

There are three possible pathways of the reactions of hydrides with unsaturated hydrocarbons a) the addition of hydride to the multiple bond [18, 27, 55, 56], b) the polymerization or the oligomerization of olefine [18, 21, 57] and c) the hydrogenation of olefin (when the reaction is carried out in H2 atmosphere) [55, 58]. All three processes apparently begin with the formation of an adduct in which the added ligand is T - or T - bonded with the metal. When an excess of the olefine is used, the following insertion of it into the a-bond Ln-R leads to a polymer or oligomer. In the... 

General methods of obtaining functionalized HRs with carboxylic groups include thermal grafting with initiators forming free radicals, or with cationic catalysts of the Friedel-Crafts type. Also included are cationic co-oligomerization of unsaturated hydrocarbons or of some Diels-Alder adducts (obtained from dienic hydrocarbons) with MA or other filodienes with carboxylic functions [155,1561. 

Unsaturated fluorinated compounds are fundamentally different from those of hydrocarbon chemistry. Whereas conventional alkenes are electron rich at the double bond, fluoroal-kenes suffer from a deficiency of electrons due to the negative inductive effect. Therefore, fluoroalkenes react smoothly in a very typical way with oxygen, sulfur, nitrogen and carbon nucleophiles.31 Usually, the reaction path of the addition or addition-elimination reaction goes through an intermediate carbanion. The reaction conditions decide whether the product is saturated or unsaturated and if vinylic or allylic substitution is required. Highly branched fluoroalkenes, obtained from the fluoride-initiated ionic oligomerization of tetrafluoroethene or hexafluoropropene, are different and more complex in their reactions and reactivities. 

Unsaturated fluorocarbons are much more reactive toward nucleophiles than then hydrocarbon counterparts owing to fluorine s ability to both stabilize carban ions and inductively increase the electrophihcity of multiple bonds and aromauc rings Nucleophilic attack dominates the chemistry of unsaturated fluorocarbons, and the role of fluoride ion in fluorocarbon chemistry is analogous to that of the proton in hydrocarbon chemistry [729] Lake the related electrophilic reactions for hydrocarbons, there are fluoride-promoted isomenzations and dimerizations (equation 9), oligomerizations (equation 10), additions (equation 11), and amomc Fnedel-Crafts alkylations (equation 12) that all proceed via carbamomc intermediates [729 141]... 

Lithium naphthalene and sodium naphthalene (11) in solvents such as THF, diglyme, or aliphatic amines were found to be effective agents for the hydrodimerization of isoprene. Although this reaction is not strictly catalytic, it contributes to a better understanding of the base-catalyzed oligomerization of unsaturated conjugated hydrocarbons. 

The difference in Cs-hydrocarbon concentrations observed for Pt/Ga-silicate and Ga-silicate can be related to the Pt reactivity in hydrogen spillover. Since Cs-hydrocarbons are likely to be Cs-dimer cracking products produced over acidic sites, they can also be involved in subsequent oligomerization reactions over acidic sites, too. Cs-hydrocarbon reactions are more probable than Cs-hydrocarbon reactions, because C3-hydrocarbons are more volatile. However, Cs-unsaturated intermediates are rapidly hydrogenated over Pt/Ga-silicate by hydrogen which was activated on platinum and spills over the acidic sites. Consequently, they did not participate in further conversion and their concentration remained constant. The platinum hydrogenation activity was confirmed by the data on the hydrogen effect on the activity for Pt/Ga-silicate and Ga-silicate. 

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