Olefin trimerization

Reactions of TaCfr with alkylating agents such as MeLi are believe to give in situ TaCl3Me2, which catalyzes selective trimerization of ethene to 1-hexene. Theoretical studies of the detailed mechanism of the olefin trimerization provide insights why this catalyst selectively trimerizes rather than dimerizes or polymerizes ethene. 

SASOL [C2dmim][NTf2] ILs in metathesis olefin trimerization. Self-metathesis of oct-l-ene to yield tetradec-7-ene and ethene... 

The stringency of the conditions employed in the unmodified cobalt 0x0 process leads to formation of heavy trimer esters and acetals (2). Although largely supplanted by low pressure ligand-modified rhodium-catalyzed processes, the unmodified cobalt 0x0 process is stiU employed in some instances for propylene to give a low, eg, - 3.3-3.5 1 isomer ratio product mix, and for low reactivity mixed and/or branched-olefin feedstocks, eg, propylene trimers from the polygas reaction, to produce isodecanol plasticizer alcohol. 

The feedstock, usuaHy consisting of propylene and butylenes (various isomers of C Hg) from cracking processes, may even consist of selective olefins for dimer, trimer, or tetramer production ... 

Highly Branched Acids. These acids, called neoacids, are produced from highly branched olefins, carbon monoxide, and an acid catalyst such as sulfuric acid, hydrogen fluoride, or boron trifluoride. 2,2,2-Trimethylacetic acid (pivaUc acid) is made from isobutylene and neodecanoic acid is produced from propylene trimer (see Carboxylic Acids, trialkylacetic acids). 

Other olefins applied in the hydroformylation process with subsequent hydrogenation are propylene trimer and tetramer for the production of decyl and tridecyl alcohols, respectively, and C7 olefins (from copolymers of C3 and C4 olefins) for isodecyl alcohol production. 

The addition of one olefin molecule to a second and to a third, etc. to form a dimer, a trimer, etc. is termed oligomerization. The reaction is normally acid-catalyzed. When propene or butenes are used, the formed... 

The minor products are generally 1-3% of the total yield and arose from (a) side-chain fragmentation producing hydrogen and low-molecular-weight hydrocarbons (b) addition of these fragments to the free olefin (c) dimerization and trimerization of the free olefin (d) fragmentation of the alkyl radical and cation intermediates. 

This has been found to be a general reaction for many types of olefins. It has also been applied to highly branched structures, such as 2,4,4-trimethyl-2-pen-tane and propylene trimers and tetramers [177], to unbranched olefins with internal double bonds, such as methyl oleate [178] and tricosane, and to a-ole-fins [179], In all cases the data indicate that the reaction occurs at the double... 

Meier et al. have also contributed to the field of cyclic PAV oligomers with the synthesis of cyclic dl -trans (all- ) trimers (e.g. 113) containing alkoxy-substituted 1,7-naphthylene and 1,9-phenanthrylene building blocks, via a Siegrist-type trimerizing olefination [134,135]. Suitable substitution at the periphery of the cyclic trimers allows for the formation of stable, thermotropic discotic mesophases [134]. 

Another highly active chromium-based catalyst family is the triazacyclohexane series (103).269 Activities are dependent upon the length of the alkyl substituents attached to the nitrogen donors, reaching 717 g mmol- 1h 1 bar-1 for R = n-dodecyl. With higher a-olefins, or when branched R substituents such as 3-propyl-heptyl are employed, these compounds behave as trimerization catalysts 270,271... 

Let us return to the thermal decomposition of Fe(CO)(l,3-C4H6)2. Once the calibration constant is known, the enthalpy of the net process 9.10 can be calculated as the product of s and the area (A + B). The next step is to correct this value to 298.15 K by using heat capacity data. This exercise is, however, complicated by the cyclobutadiene polymerization. Brown et al. analyzed the reaction products by mass spectrometry and found several oligomers, in particular the dimer (C4H6)2 and the trimer (C4H6)3 [163]. With such a mixture, it is difficult to ascribe the observed enthalpy change to a well-defined chemical reaction. This is discussed in the paper by Brown and colleagues, who were nevertheless able to recommend a value for the standard enthalpy of formation of the iron-olefin... 

In 55 to 80% aqueous H2SO4 the simple alcohol olefin equilibrium (found in 0-55% H2SO4) is complicated by a polymerization process which produces predominantly dimer, trimer, and some traces of higher boiling olefins. This behaviour was first noticed by Butlerow (1879). Two fundamental papers by Whitmore (1932, 1934) first presented the now generally accepted mechanistic pathway with carbonium ion... 

Olefins possessing allylic hydrogens undergo reactions similar to those of aromatics with benzylic hydrogen. These reactions lead to combination of the olefins, usually to dimers and trimers. 

Zirconium hydride(s) supported on oxide materials catalyze several classical reactions such as hydrogenation, reductive cyclizahon, cyclo-trimerization and olefin polymerization [43-47]. Notably, it also catalyzes the hydrogenolysis of polyolefins... 

Phosphinodihydroxazole (PHOX) compounds, L2-4, act as P/N bidentate ligands showing excellent enantioselectivity in Ir-catalyzed hydrogenation of simple a,a-disubstituted and trisubstituted olefins (Figure 1.12). " The use of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArp) as a counter anion achieves high catalytic efficiency due to avoidance of an inert Ir trimer... 

Triosmium dodecacarbonyl reacts with the simple ligand vp in an atypical manner 37) the trimeric osmium nucleus is retained and the olefin attacked to give a complex of formula Os3(CO)8(vp), which has two hydrides attached to osmium atoms. These are possibly a and one / -hydrogen of the olefin, the remainder being r-bonded to the trimeric osmium core. 

In polymerization an olefin can react with another olefin to generate dimers, trimers, and tetramers of the olefin. As a simple example, isobutylene reacts to give a highly branched Cg olefin. 

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