The studies described in this paper show that hydrocarbon oligomers are alternatives for low molecular weight alkane solvents. These oligomeric solvents are nontoxic, nonvolatile, and recyclable alternatives to heptane in thermomorphic solvent mixtures that use a polar solvent such as methanol, aqueous ethanol, or DMF or in biphasic mixtures that use acetonitrile. Regardless of which polar solvent is used, hydrocarbon oligomers like poly(α-olefin)s (PAOs) exhibit very low leaching into the polar phase. UV-visible spectroscopy studies show that these solvents have the solubility properties of heptane. For example, PAOs dissolve heptane soluble dyes and quantitatively separate them from polar phases in thermomorphic solvent mixtures. PAOs either as pure solvents or as additives in heptane act as antileaching agents, decreasing the already low leaching of such dyes into a polar phase in heptane/polar solvent mixtures. These oligomeric hydrocarbon solvents were also compared to heptane in studies of azo dye isomerization. The results show that thermal isomerization of an azo dye occurs at the same rate in heptane and a PAO. Further studies of carboxylic acid promoted dye isomerization in heptane and a PAO show that low molecular weight and oligomeric carboxylic acids are kinetically equivalent at accelerating this isomerization. The results suggest that these and other hydrocarbon oligomers behave as solvents like their low molecular weight nonpolar hydrocarbon solvents and that they can be substituted successfully for conventional solvents like heptane.
Low‐viscosity poly(α‐olefin)s (PAOs) either alone or with functional hydrocarbon oligomer cosolvents are nontoxic, nonvolatile, recyclable solvent systems that effectively and efficiently sequester trace amounts of nonpolar organic compounds such as benzene and halogenated organics from water. More polar compounds including perfluorooctanoic acid and nitrobenzene or water‐miscible compounds such as THF and triethylamine can also be sequestered if the PAO phase contains an H‐bonding PAO‐anchored cosolvent.
This study describes the use of polyisobutylene
(PIB) to phase-anchor
pyridine ligands that form a phase-separable Grubbs third-generation
catalyst. We further show that this complex is useful in ring-opening
metathesis polymerization (ROMP) reactions. These PIB-bound pyridine-ligated
Grubbs catalysts provide the same benefits of control over polymer
chain growth and polydispersity of the product as their low-molecular-weight
analogs and reduce Ru leaching in ROMP products from approximately
16% (820 ppm residues) as seen with a similar pyridine-ligated catalyst
to a value of approximately 3% (160 ppm residues). These labile ligands
are shown to be as effective at generating separable metal complexes
as less labile PIB-functionalized N-heterocyclic carbene catalyst
ligands that are typically used for immobilization but that require
a multistep synthesis.
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