1-hexene solubility

Figure 5.3-4 Turnover frequency of Rh-catalyzed hydroformylation as a function of 1-hexene solubility in ionic liquids. Reactions conditions Rh(CO)2(acac) 0.075 mmol, 1 -hexene/Rh = 800, TPPTS/Rh = 4, heptane as internal standard, CO/Hj = 1 (molar ratio), P = 2 MPa, T = 80 °C, TOP determined at 25 % conversion of 1 -hexene ([BMP]= N,N-butylmethylpyrolidinium [BMMIM] = 1-butyl-2,3-dimethylimidazolium)...

Literature indicates that in the presence of olefins like 1-hexene, solubility of both CO and hydrogen is substantially increased and hence a rate enhancement higher than first order is observed (16). 

Hexene solubility with [BMIM] as cation Bp4 < Pp0 < TfO < Cp3S02 < Tf2N ... 

Figure 7.14 Typical cations and salts of ionic liquids and the order of 1-hexene solubility in [BMIM][X] in dependence on the anion X.

Figure 5.3-1 Solubility of 1-hexene in different ionic liquids as a function of the nature of...

In the rhodium-catalyzed hydroformylation of 1-hexene, it has been demonstrated that there is a correlation between the solubility of 1-hexene in ionic liquids and reaction rates (Figure 5.3-4) [28]. 

It is possible to synthesize cobalt complexes which are soluble in polyethylene glycols and not in. solvents like hexane, hexene, heptenal etc. Ritter et al. (1996) have reported the oxo reaction of 1-hexene in such a system. 

The substituted-cyclopentadiene derivatives analogs of [Cp2Zr(H)Cl]n (1), (MeCp)2Zr(H)Cl (2) [38], Cp CpZr(H)Cl (3) [39], and [(Me2Si)(C5H5)2Zr(H)Clj [40] are more soluble in non-polar organic solvents, and consequently they are more reactive. Thus, the direct competition between 1 and 2 for the hydrozirconation reaction of 1-hexene affords predominantly (86%) the product derived from the methylated derivative (Scheme 8-3) [41]. 

As described in Section 9.1.2.2.3, several lanthanocene alkyls are known to be ethylene polymerization catalysts.221,226-229 Both (188) and (190) have been reported to catalyze the block copolymerization of ethylene with MMA (as well as with other polar monomers including MA, EA and lactones).229 The reaction is only successful if the olefin is polymerized first reversing the order of monomer addition, i.e., polymerizing MMA first, then adding ethylene only affords PMMA homopolymer. In order to keep the PE block soluble the Mn of the prepolymer is restricted to <12,000. Several other lanthanide complexes have also been reported to catalyze the preparation of PE-b-PMMA,474 76 as well as the copolymer of MMA with higher olefins such as 1-hexene.477... 

Reported aqueous solubilities of 1 -hexene at various temperatures... 

FIGURE 2.1.2.1.10.1 Logarithm of mole fraction solubility (In x) versus reciprocal temperature for 1-hexene. 

Platinum on carbon did almost exactly the same thing but required a temperature of about 100°C to do so. With excess acetylene, only III formed. With tcrt-butylacetylene no II formed, probably because of steric hindrance, but I and III formed readily. 3-Hexyne reacted more slowly, required heat with chloroplatinic acid, and formed exclusively c/s-3-di-chlorosilyl-3-hexene. Trichlorosilane with platinum on carbon also added (57) to 1-alkynes or to phenylacetylene exclusively by cis addition to give only trans adducts. Later works (55) indicate that chloroplatinic acid and other soluble catalysts also give exclusively cis addition with a wide variety of Si—H compounds. 

Soluble metathesis catalysts yield trans products in reactions with // / v-2-pentene, but generally are not very stereospecific with c/.v-2-pen-tene. In the latter case, the initially formed butenes and hexenes are typically about 60 and 50% cis, respectively. Basset noted (19) that widely diverse catalyst systems behaved similarily, and so it was suggested that the ligand composition about the transition metal was not a significant factor in the steric course of these reactions. Subsequently, various schemes to portray the stereochemistry have been proposed which deal only with interactions involving alkyl substituents on the reacting olefin or on the presumed metallocyclobutane intermediate. 

In 2004, Pardey et al.170 reported hydroformylation activity of 1-hexene and styrene for water soluble Rh2(p-Pz)2(CO)2(TPPMS)2. 

Water-soluble l,3-bis(di(hydroxyalkyl)phosphino)propane derivatives were thoroughly studied as components of Pd-catalysts for CO/ethene (or other a-olefins) copolymerization and for the terpolymerization of CO and ethene with various a-olefins in aqueous solution (Scheme 7.17) [59], The ligands with long hydroxyalkyl chains consistently gave catalysts with higher activity than sulfonated DPPP and this was even more expressed in copolymerization of CO with a-olefins other than ethene (e.g. propene or 1-hexene). Addition of anionic surfactants, such as dodecyl sulfate (potassium salt) resulted in about doubling the productivity of the CO/ethene copolymerization in a water/methanol (30/2) solvent (1.7 kg vs. 0.9 kg copolymer (g Pd)" h" under conditions of [59]) probably due to the concentration of the cationic Pd-catalyst at the interphase region or around the micelles which solubilize the reactants and products. Unfortunately under such conditions stable emulsions are formed which prevent the re-use... 

Similar to the above case, hydroformylation of 1-hexene using a water-soluble rhodium catalyst [RhH(CO)(TPPMS)3] gave lower yields when a-cyclodextrin was added to the biphasic reaction system [14]. Again, the reason was suspected in the interaction between the cyclodextrin and the rhodium catalyst. 

The solubilities of aromatic compounds in the ionic liquid are dramatically higher than those of saturated compounds. Benzene has a solubility of 4.9mol/mol of ionic liquid, and thiophene has a solubility of 6.7mol/mol of ionic liquid. A dramatic steric effect was observed on the solubility of aromatics the alkyl-substituted aromatics showed reduced solubility. Although the solubility of hexene in the ionic liquid is considerably lower than that of the aromatics, it is still measurably higher than that of hexane. Similar structure-solubility relationships characteristic of organic molecules were observed with the ionic liquids [BMIM]BF4, [BMIM]PFg, and [EMIM]BF4 (Fig. 10) (27). 

An ionic liquid was fully immobilized, rather than merely supported, on the surface of silica through a multiple-step synthesis as shown in Fig. 15 (97). A ligand tri(m-sulfonyl)triphenyl phosphine tris(l-butyl-3-methyl-imidazolium) salt (tppti) was prepared so that the catalyst, formed from dicarbonylacetylacetonate rhodium and the ligand (P/Rh = 10), could be soluble in both [BMIMJBFq and [BMIM]PF6. The supported ionic liquid-catalyst systems showed nearly three times higher rate of reaction (rate constant = 65 min ) that a biphasic system for the hydroformylation of 1-hexene at 100°C and 1500 psi in a batch reactor, but the n/i selectivity was nearly constant the same for the two ( 2.4). Unfortunately, both the supported and the biphasic ionic liquid systems exhibited similar metal leaching behavior. 

Hydrocarbon bond saturation and cyclization also play roles in water solubility. Figure 6.7 shows that, among the six-carbon hydrocarbons, the various forms of hexane, C6H14, have the lowest solubility, and the hexenes and cyclohexane with the formula C6H12 have three times the solubility. Fewer hydrogen atoms consistently lead to higher solubilities, and benzene has one hundred times the water solubility of normal and iso-hexanes. 

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