Copper solvent effects

The importance of solvent effects in the preparation of perfluoroalkyzinc reagents is further illustrated in the reaction of perfluoroalkyl iodides with zinc-copper couple. In DMSO, DMF, and HMPA, the main products are the fluo-roolefins The formation of the fluoroolefin is facilitated when the reaction is carried out in the presence of potassium thiocyanate [30] (equation 21)... 

This interesting solvent effect was explained by Baro et al. on the basis of the formation of cyclic dimers (13.7) as suggested earlier by Hunter (1937) and by Le Fevre and Vine (1937). It was later confirmed in an X-ray investigation by Omel chenko and Kondrashev (1967). The X-ray analysis of 1,3-diphenyltriazene copper(i) (Brown... 

Jorgensen et al. [84] studied how solvent effects could influence the course of Diels-Alder reactions catalyzed by copper(II)-bisoxazoline. They assumed that the use of polar solvents (generally nitroalkanes) improved the activity and selectivity of the cationic copper-Lewis acid used in the hetero Diels-Alder reaction of alkylglyoxylates with dienes (Scheme 31, reaction 1). The explanation, close to that given by Evans regarding the crucial role of the counterion, is a stabilization of the dissociated ion, leading to a more defined complex conformation. They also used this reaction for the synthesis of a precursor for highly valuable sesquiterpene lactones with an enantiomeric excess superior to 99%. 

Kitchens, C.L., McLeod, M.C. and Roberts, C.B. (2003) Solvent effects on the growth and steric stabilization of copper metallic nanoparticles in AOT reverse micelle systems. Journal of Physical Chemistry B, 107 (41), 11331-11338. 

Otto et al. studied asymmetric Diels-Alder reactions in the presence of the copper salts of glycine, L-valine, L-leucine, L-phenylalanine, L-tyrosine, l-tryptophan, and /V-a-L-tryptophan (L-abrine). The copper salt of L-abrine gave the highest enantioselectivity. Table 5 3 compares the solvent effect in this reaction, and clearly water is the best solvent among the solvent systems studied. 

TABLE 7.3 Solvent Effect on Enantioselectivity Catalysis by Copper (L-abrine) as the Lewis Acid... 

Examples of preparation of copolymers are scarce. Mun et al. [81, 82] showed that the binary system of cobaltocene/ bis(ethylacetoacetato) copper (II) effectively initiates the living radical polymerizaton of MMA at 25 °C in acetonitrile. The polymerization activity of this initiator system was markedly affected by the solvent used. The synthesis of PMMA-b-PS copolymers with molecular weights reaching 700000 was successfully attempted by adding styrene to the living PMMA. The yield of the copolymers reached 80% when the MMA polymerization was carried out for three days. The same team [91] also synthesized PS-b-PMMA copolymers from the polymerization of MMA with polystyrene obtained in the presence of reduced nickel/halide systems. The yields range from 84 to 91% depending on the halide complex used. 

In these complicated extraction systems containing the polymeric and/or hydroxo species, one would expect the solvent used as a diluent to exert a considerable effect on the extraction equilibrium. In the extraction of gallium (III) with decanoic acid it has been found that the less polar the solvent, the more polymerized the extracted species (150). More recently, the solvent effect on the extraction (156) and dimerization (151, 153) of copper(II) decanoate has been interpreted according to regular solution theory (141,142). 

As predicted from Eq. (21), log cx(262) is indeed linearly related with (<5W — d0)(d + d0 — 1.03<5(HA)2) with the theoretical slope of — 0.13 VlHA)JRT. Equation (21) describes the solvent effect on the copper decanoate extraction very nicely (156). 

Decarboxylation (solvent effect). Casini and Cioudman found lhal decarboxylation of 7-nitroindole-2-carboxylic acid by heating with a catalytic amount of the copper salt of the acid proceeded in higher yield and with simpler isolation of product when N,N-dimethylacetamide was used as solvent rather than the conventional quinoline. 

HEMA) [212]). Monomer 42 (MFC) spontaneously polymerizes at room temperature in aqueous solution and the choice of the slowest catalyst is therefore justified. Because poly-38 [212] is not soluble in water, the polymerization is run in a 50 50 MeOH water mixture. Consequently, rates are lower than in water (95% conversion requires 3-4 h reaction time at room temperature). A comparison of polymerization rates in aqueous and non-aqueous media reveals strong solvent effects. Polar solvents have been found to increase the polymerization rate, possibly because of the combined effect of an increase of rate constant [213] and a competitive coordination of the solvent and the ligand in the copper species [214]. 

Calvin, M., Belford, G.(1957) Bonding in copper(II) chelates solvent effects on their visible solution spectra. J. Chem. Phys. 26, 1165. 

The diluent in a sol van t extraction system does not serve simply as an inert carrier for the extractant and its metal compounds, it has been found repeatedly that the choice of diluent can affect significantly the perfomience of various extractants, presumably through both chemical and physical interactions with the solute species. For example. Mutiny and Bouboulis9 reported the effects of systematically varying the aromatic content of cha diluent on a copper extraction process, and Akiba aud F reiser5 demonstrated solvent effects on system chemistry. Ritcey and Ashbrook10 review the various solvent properties that influence extractant performance. 

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