CO in Aqueous Solutions

Carbon dioxide readily dissolves in water to produce the weak acid carbonic acid, H2C03. The presence of CO, in aqueous solution results in equilibria involving carbon dioxide,... 

ATI. Falchetti, A., Giavarini, C Moresi, M and Sebastian , E., Absorption of CO in aqueous solutions reaction kinetics of modified tetrac-thylenepentamine, hig. Chim. Ital.. 17, I, 1981 Chim. hid, 63, 1981. 

On quartz, however, the formation of a precipitate that has similar lattice dimensions as the surface is not favorable unless Co undergoes a coordination change from octahedral to tetrahedral. Such a coordination change is unlikely for Co in aqueous solution (70) and the XAFS spectra of the Co/quartz sorption system showed no evidence of a change. Thus, the Co hydroxide-like precipitate that formed on quartz was attached only to comers of selected Si tetrahedra on the surface. 

TABLE 3 Estimated percentage of hydrogen ions, a, resulting from the hydrolysis of Co in aqueous solutions of cobalt (ft) chloride at 298.15K, using equation similar to Equations (20) and (21) [4]. 

Empirical expressions have been reported for presenting the Setschenow constants for a large variety of solutes and ions. Weisenberger and Schumpe [63] presented an expression for gaseous solutes that do not interact chanicaUy with the solvents (excluding, e.g., NHj, HCl, and CO in aqueous solutions) ... 

Fig. 17 Enhancement factor with physical absorption of CO in aqueous solutions as a function of the activated carbon concentration in a stirred cell with O) = 1.33 s and d < 5 ym.

The absorption of COS in aqueous solutions of MDEA was studied by Al-Ghawas et al. (1988). They concluded that the overall reaction between COS and MDEA is given by the following equation ... 

Thus, it can be concluded that bimetalhc complex (C0M04CA) with stmcture described in [6,13] can be obtained using any of the above specified compounds of Mo and Co in aqueous solutions containing components with the molar ratio of Mo/CA/ Co=2/1.2/l and pH laying in the range of 2.0-3.5. 

Copper(II) salts (blue in aqueous solution) are typical M(II) salts but generally have a distorted co-ordination (Jahn-Teller distortion, 4 near plus 2 far neighbours). Extensive ranges of complexes are known, particularly with /V-ligands. 

Half-reaction (i) means that Co(II) in aqueous solution cannot be oxidised to Co(III) by adding ammonia to obtain the complexes in (ii), oxidation is readily achieved by, for example, air. Similarly, by adding cyanide, the hexacyanocobaltate(II) complex becomes a sufficiently strong reducing agent to produce hydrogen from water ... 

The method has severe limitations for systems where gradients on near-atomic scale are important (as in the protein folding process or in bilayer membranes that contain only two molecules in a separated phase), but is extremely powerful for (co)polymer mixtures and solutions [147, 148, 149]. As an example Fig. 6 gives a snapshot in the process of self-organisation of a polypropylene oxide-ethylene oxide copolymer PL64 in aqueous solution on its way from a completely homogeneous initial distribution to a hexagonal structure. 

Note. Methyl oxalate, unlike most other esters, hydrolyses very rapidly in aqueous solution hence it will evolve CO in the above test, owing to the formation of methanol and free oxalic acid. 

The use of indium in acpieous solution has been reported by Li and co-workers as a new tool in org nometallic chemistry. Recently Loh reported catalysis of the Mukaiyama-aldol reaction by indium trichloride in aqueous solution". Fie attributed the beneficial effect of water to a eg tion phenomena in connection with the high internal pressure of this solvenf This woric has been severely criticised by... 

Jaeger and co-workers studied the regioselectivity of the reaction of a surfactant diene with a surfactant dienophile in micellar media" ". The orientational effects in the aggregates could result in an increase in the regjoselectivity in aqueous solutions of these compounds as compared to the reaction in organic media. 

Chapter 2 describes the results of the first detailed study of Lewis-acid catalysis of a Diels-Alder reaction in water. Substituted 3-phenyl-l-(2-pyridyl)-2-propen-l-one dienophiles (la-gin Scheme 1) were found to coordinate to Co, Cu" and Zn ions in aqueous solution. This process forms... 

Oxidation. Maleic and fumaric acids are oxidized in aqueous solution by ozone [10028-15-6] (qv) (85). Products of the reaction include glyoxyhc acid [298-12-4], oxalic acid [144-62-7], and formic acid [64-18-6], Catalytic oxidation of aqueous maleic acid occurs with hydrogen peroxide [7722-84-1] in the presence of sodium tungstate(VI) [13472-45-2] (86) and sodium molybdate(VI) [7631-95-0] (87). Both catalyst systems avoid formation of tartaric acid [133-37-9] and produce i j -epoxysuccinic acid [16533-72-5] at pH values above 5. The reaction of maleic anhydride and hydrogen peroxide in an inert solvent (methylene chloride [75-09-2]) gives permaleic acid [4565-24-6], HOOC—CH=CH—CO H (88) which is useful in Baeyer-ViUiger reactions. Both maleate and fumarate [142-42-7] are hydroxylated to tartaric acid using an osmium tetroxide [20816-12-0]/io 2LX.e [15454-31 -6] catalyst system (89). 

Ozone in the gas phase can be deterrnined by direct uv spectrometry at 254 nm via its strong absorption. The accuracy of this method depends on the molar absorptivity, which is known to 1% interference by CO, hydrocarbons, NO, or H2O vapor is not significant. The method also can be employed to measure ozone in aqueous solution, but is subject to interference from turbidity as well as dissolved inorganics and organics. To eliminate interferences, ozone sometimes is sparged into the gas phase for measurement. 

Syntheses in Solvent Systems. Very few examples of syntheses of metal carbonyls in aqueous solution are reported. An exception is the preparation of Co2(CO)g from CoSO (66% yield) or C0CI2 (56% yield) and CO at 9.6—11 MPa (95—110 atm) in aqueous ammonia at 120°C for 16—18 h (101). Triiron dodecacarbonyl is prepared almost exclusively in aqueous solution. Quantitative yields of Fe2(CO)22 have been obtained by oxidising alkaline solutions of carbonyl ferrates with manganese dioxide (102—104). 

Studies on metal-pyrazole complexes in solution are few. The enthalpy and entropy of association of Co(II), Ni(II), Cu(II) and Zn(II) with pyrazole in aqueous solution have been determined by direct calorimetry (81MI40406). The nature of the nitrogen atom, pyridinic or pyrrolic, involved in the coordination with the metal cannot be determined from the available thermodynamic data. However, other experiments in solution (Section 4.04.1.3.3(i)) prove conclusively that only the N-2 atom has coordinating capabilities. 

TABLE 23-8 Correlation of Kgo for Absorption of CO by Aqueous Solutions of Monoethanolamine in Packed Towers ... 

The coordination chemistry of Zn" and Cd", although much less extensive than for preceding transition metals, is still appreciable. Neither element forms stable fluoro complexes but, with the other halides, they form the complex anions [MX3] and [MX4] , those of Cd" being moderately stable in aqueous solution. "" By using the large cation [Co(NH3)6] + it is also possible to isolate the trigonal bipyramidal [CdCls] "... 

A. Miilier and co-workers [Ber, deut. Chem. Ges. 76, 856 (1943) Ber. deut. chem. Ges. 75, 891 (1942) Acta Chim. Acad. Sci. Hung., in press observed similar behavior with some isobenzopyrylium salts. If warmed in aqueous solution they are transformed into isobenzop5Tapols and these change on warming in ethyl acetate into the isomeric diketoues by ring opening. 

Copper electrodeposition on Au(111) Copper is an interesting metal and has been widely investigated in electrodeposition studies from aqueous solutions. There are numerous publications in the literature on this topic. Furthermore, technical processes to produce Cu interconnects on microchips have been established in aqueous solutions. In general, the quality of the deposits is strongly influenced by the bath composition. On the nanometer scale, one finds different superstmctures in the underpotential deposition regime if different counter-ions are used in the solutions. A co-adsorption between the metal atoms and the anions has been reported. In the underpotential regime, before the bulk deposition begins, one Cu mono-layer forms on Au(lll) [66]. 

Suspension (co)polymerization is carried out in aqueous solutions of monomers dispersed in the form of 0.1-5 mm diameter droplets by stirring in nonmixed water-organic liquids in the presence of initiators. The organic liquids that are not dissolving monomers and (co)polymers are represented by solvents that either form azeotropic water mixtures (toluene, heptane, cy-... 

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