Aqueous Systems with Additional Organic Solvent

2 Aqueous Systems with Additional Organic Solvent 

Triphenylphosphane monosulfonate (sodium salt) and triphenylphosphine disulfonate (disodium salt) were compared in one study with TPPTS and the results showed that each ligand together with 1.0mol% palladium catalyst is similarly effective for the Mizoroki-Heck reaction of iodobenzene with an olefin [162], Leaching levels are also comparable the percentaged leaching represents the amount of palladium contamination 

An intramolecular Mizoroki-Heck reaction was carried out with Pd(OAc)2 (10 mol%) in the presence of P(o-tol)3 in an acetonitrile-water mixture [182], while another group used the same solvent mixture in an intramolecular Mizoroki-Heck reaction with alkoxy groups as leaving groups [183, 184]. The reaction was conducted at room temperature in the presence of Pd(OAc)2 (10 mol%) and a variety of phosphine ligands tpp, P(o-tol)3, P(p-tol)3, P(2-furyl)3, diphenylphosphinopropane, diphenylphosphinobutane and diphenylphosphi-noferrocene. 

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Ultrasound in combination with an organic solvent facilitates the formation of binary systems with an aqueous electrolyte, thereby increasing the current intensity Figure 8.14B shows this effect on the sono-voltammogram of A/,A/,A/, /V -tetramethyl-p-phenylenediamine (TMPD) in 0.1 M aqueous KCI with and without the addition of 40% v/v heptane [156]. The increased current in the acoustically emulsified media was ascribed to enhanced transport of electroactive material in heptane droplets towards the electrode surface, and related to the analyte solubility in the organic phase. The ratio of the current increase to the volume fraction of organic solvent ([Pg.286]

The method in which palladium complexes with hydrophilic phosphines are used in a biphasic system of water-organic solvent can be considered complementary to the standard protocol. In this case, boronate and palladium catalyst reside in the aqueous phase, while halide substrate is in the organic phase. In order for the reaction to run, the latter should be partitioned into the aqueous phase. Alternatively, oxidative addition may occur at the interface. Due to the low efQcienc of both methods, high loads of palladium catalyst and phosphine are required. Recycling is possible but is hampered by the accumulation of inorganic salts (hahde, borate) in the aqueous layer. 

High molecular weight primary, secondary, and tertiary amines can be employed as extractants for zirconium and hafnium in hydrochloric acid (49—51). With similar aqueous-phase conditions, the selectivity is in the order tertiary > secondary > primary amines. The addition of small amounts of nitric acid increases the separation of zirconium and hafnium but decreases the zirconium yield. Good extraction of zirconium and hafnium from ca 1 Af sulfuric acid has been effected with tertiary amines (52—54), with separation factors of 10 or more. A system of this type, using trioctylarnine in kerosene as the organic solvent, is used by Nippon Mining of Japan in the production of zirconium (55). 

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