Oxides in aqueous solution

Perchlorates. Iron(II) perchlorate hexahydrate [13922-23-8], Fe(C10 2 6H20, is prepared by dissolving iron in cold, dilute perchloric acid or by dissolving FeS in perchloric acid. It crystallizes in hygroscopic, light green hexagonal prisms which are stable in dry air and extremely soluble (0.978 g/mL H2O at 0°C) in water and alcohol. It is susceptible to air oxidation in aqueous solution and decomposes above 100°C. Yellow iron(III) perchlorate... 

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). 

Only slightly less accurate ( 0.3—0.5%) and more versatile in scale are other titration techniques. Plutonium maybe oxidized in aqueous solution to PuO " 2 using AgO, and then reduced to Pu" " by a known excess of Fe", which is back-titrated with Ce" ". Pu" " may be titrated complexometricaHy with EDTA and a colorimetric indicator such as Arsenazo(I), even in the presence of a large excess of UO " 2- Solution spectrophotometry (Figs. 4 and 5) can be utilized if the plutonium oxidation state is known or controlled. The spectrophotometric method is very sensitive if a colored complex such as Arsenazo(III) is used. Analytically usehil absorption maxima and molar absorption coefficients ( s) are given in Table 10. Laser photoacoustic spectroscopy has been developed for both elemental analysis and speciation (oxidation state) at concentrations of lO " — 10 M (118). Chemical extraction can also be used to enhance this technique. 

Iron Reduction. The reduction of nitrophenols with iron filings or turnings takes place in weakly acidic solution or suspension (30). The aminophenol formed is converted to the water soluble sodium aminopheno1 ate by adding sodium hydroxide before the iron-iron oxide sludge is separated from the reaction mixture (31). Adjustment of the solution pH leads to the precipitation of aminophenols, a procedure performed in the absence of air because the salts are very susceptible to oxidation in aqueous solution. 

With hot metals, sulfur dioxide usually forms both metal sulfides as well as metal oxides. In aqueous solution, sulfur dioxide is reduced by certain metals or by borohydrides to dithionites. 

This is the only oxidation state which, with the possible exception of Pa, is displayed by all actinides. From U onwards, its resistance to oxidation in aqueous solution increases progressively with increase in atomic number and it becomes the most stable oxidation state for Am and subsequent actinides (except No for which the f " configuration confers greater stability on the +2 state). 

Zhou, Z Chu, B, Light-Scattering Study on the Association Behavior of Triblock Polymers of Ethylene Oxide and Propylene Oxide in Aqueous Solution, Journal of Colloid and Interface Science 126, 171, 1988. 

Hart and Henglein [14] also reported the sonolytic decomposition of nitrous oxide in aqueous solutions under pure argon, pure N2O and the mixture of the two gases and reported the formation of species such as N2, O2, N02 and N03 with the maximum yield being in the Ar/N20 mixture in the vol% ratio of 85 15. Although H20 is thermodynamically much more stable than N2O but they postulated that all H20 and N2O molecules in an argon bubble were converted into free radicals in the short time of adiabatic compression phase of the bubble. They proposed a series of free radical reactions for the formation of all these species in aqueous solutions. 

Hart Edwin J, Henglein Amim (1986) Sonolytic decomposition of nitrous oxide in aqueous solution. J Phys Chem 90 5992-5995... 

F. Lantoine, S. Trevin, F. Bedioui, and J. Devynck, Selective and sensitive electrochemical measurement of nitric-oxide in aqueous-solution - discussion and new results. J. Electrocmal. Chem. 392, 85-89 (1995). 

The UV/Vis, Mossbauer, EXAFS, and EPR spectroscopic data suggest a rather complicated picture regarding the speciation of oxidized TAML species derived from 1 and various oxidants in aqueous solution (Scheme 5). Peroxides ROOH have the capacity to function as two-electron oxidants and usually do. In cases where prior coordination occurs, they can oxidize metal ions via one-electron processes where the 0-0 bond is cleaved homo-lytically or two-electron processes where it is cleaved hetero-lytically. The two-electron oxidation of 1 presumably would give the iron-oxo intermediate 6, two electrons oxidized above the iron(III) state (see below). Before 6 was actually isolated, there... 

Cataban A process for removing small amounts of hydrogen sulfide from industrial gas streams by oxidation, in aqueous solution, to elemental sulfur. The oxidant is the ferric ion,... 

We may predict many redox reactions of metals by using an activity series. An activity series lists reactions showing how various metals and hydrogen oxidize in aqueous solution. Elements at the top of the series are more reactive (active) than elements below. A reaction occurs when an element interacts with a cation of an element lower in the series. The more active elements have a stronger tendency to oxidize than the less active elements. The less active elements tend to reduce instead of oxidize. The reduction reactions are the reverse of the oxidation reactions given in the activity series table, Table 4-1. This is an abbreviated table. Refer to your textbook for a more complete table. 

G. J. Stridh. On the Slow Oxidation of Arsenic(llT) Oxide to ArsenidV) Oxide in Aqueous Solution by Elemental Oxygen and its Effect on the Precise Determination of Energies of Combustion of Organic Chloro- and Bromo-compounds. J. Chem. Thermodynamics 1975, 7, 703-705. 

RNHCT oxidation in aqueous solution at pH 13 at an Hg anode (Iversen and Lund, 1969). RNHO oxidation in dimethyl sulfoxide-Et4NBF4 at a PT anode (Bordwell and Liu, 1996) the published potentials were converted from the ferricinium/ferrocene reference to SCE by adding 0.51V (Bordwell et al., 1991). c RNHOH oxidation in acetonitrile-NaC104 at a glassy carbon anode (Sayo et al, 1973 Ozaki and Masui, 1978). 

Fig. 12.7 (a) Fabrication schematic of a graphene-encapsulated metal oxide, (b) Zeta potentials of APS-modified silica ( ) and graphene oxide ( ) in aqueous solutions with various pH values, (c) and (d) typical SEM, and (e) transmission electron microscopy (TEM) images of graphene-encapsulated silica spheres. Reprinted with permission from [87]. Copyright 2010, John Wiley Sons, Inc. 

Fig. 8-28. Cathodic polarization curves for several redox reactions of hydrated redox particles at an n-type semiconductor electrode of zinc oxide in aqueous solutions (1) = 1x10- MCe at pH 1.5 (2) = 1x10 M Ag(NH3) atpH12 (3) = 1x10- M Fe(CN)6 at pH 3.8 (4)= 1x10- M Mn04- at pH 4.5 IE = thermal emission of electrons as a function of the potential barrier E-Et, of the space charge layer. [From Memming, 1987.]...

Figure 8-30 shows the normalized cathodic transfer current of redox electrons for several redox reactions as a function of the standard redox potential sbdox on n- semiconductor electrodes of zinc oxide in aqueous solutions. The bell-like curve observed in Fig. 8-30 is in agreement with the forgoing conclusion that the maximum current occurs at the electrode potential at whidi tox equals e. ... 

For metal oxide electrodes, the iso-electric point pH p is also located midway between the unitary acidic proton level and the unitary basic proton level of adsorbed water. Table 9-1 shows the iso-electric point pHi, of several metal oxides in aqueous solutions. 

TABLE 9-1. Iso-electric point pHi, of metal oxides in aqueous solution. [From Aikawa, 1992.]... 

Fig. 11-8. Polarization curves for a corroding metallic electrode of which corrosion rate is controlled by diffusion of oxidants in aqueous solution solid curve = observable polarization curve.

Zafiriou, O.C. and McFarland. M. Determination of trace levels of nitric oxide in aqueous solution. Anal Chem., 52(11) 1662-1667, 1980. 

When early transition metals are considered, the synthesis is essentially accomplished by dissolving the appropriate metal oxide in aqueous solutions of hydrogen peroxide. 

Table V. Rate Constants (60°) for Chain Propagation and Termination and Pre-exponential Factors and Activation Energies for Methyl Ethyl Ketone Oxidation in Aqueous Solutions...

When methyl ethyl ketone is oxidized in aqueous solutions, the over-all reaction rate drops because of solvation of the peroxy radicals, and w1 decreases more than w2. The reaction rates for formation of methyl ethyl ketone oxidation products in aqueous solutions are shown, as an example, in Tables VII and VIII. 

In the discussion that follows, we focus on the kinetic studies of S(IV) oxidations in aqueous solutions. However, it must be recognized that the oxidation itself is only one portion of a sequence of processes that leads from gas-phase S02 to aqueous-phase sulfate. The sequence of steps, depicted in Fig. 8.11, is as follows ... 

Brandt, C., I. Fabian, and R. van Eldik, Kinetics and Mechanism of the Iron(III)-Catalyzed Autooxidation of SulfuKIV) Oxides in Aqueous Solution—Evidence for the Redox Cycling of Iron in the Presence of Oxygen and Modeling of the Overall Reaction Mechanism, Inorg. Chem., 33, 687-701 (1994). 

Martin, L. R., Kinetic Studies of Sulfite Oxidation in Aqueous Solutions, in S02, NO, and N02 Oxidation Mechanisms Atmospheric Consideration, Acid Precipitation Series, pp. 63-100 and references therein (J. I. Teasley, Series Ed.), Butterworth, Stone-ham, MA, 1984. 

Cobaltous bromide and cobaltous iodide in the solid state absorb ammonia with formation of hexammino-cobaltous bromide, [Co(NH3)6]Br2, and hexammino - cobaltous iodide, [Co(NH3)6]I2, respectively. The compounds are unstable, and rapidly lose ammonia on heating and decompose on solution in water. Tetrammino-cobaltous iodide, [Co(NH3)4]I2, is also known. It may be prepared by treating a concentrated solution of cobaltous iodide with ammonia a pale red precipitate is formed, which gradually dissolves on warming, giving a violet-coloured liquid from which small rose-red crystals of the tetram-mine separate. It also is unstable, and decomposes on heating or on standing in air with loss of ammonia and formation of cobalt oxide. In aqueous solution it turns brown, ammonia is evolved, and a precipitate of cobaltous oxyiodide separates. 

Ignarro, L. J., Fukuto, J. M., Griscavage, J. M., Rogers, N. E., and Burns, R. E. (1993). Oxidation of nitric oxide in aqueous solution to nitrite but not nitrate Comparison with enzymatically formed nitric oxide from L-arginine. Proc. Nad. Acad. Sci. U.S.A. 90, 8103-8107. 

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