Oxygen in aqueous solutions

Two examples are (1) the thermal, gas-phase decomposition of acetaldehyde at high temperatures and (2) the reaction of the hydrated 2-propylchromium ion with molecular oxygen in aqueous solution. The reactions and their rate laws are as follows ... 

An example of amperometric methods used for analytical purposes is the sensor proposed in 1953 by Leland C. Clark, Jr. for determining the concentration of dissolved molecular oxygen in aqueous solutions (chiefly biological fluids). A schematic of the sensor is shown in Fig. 23.1. A cylindrical cap (1) houses the platinum or other indicator electrode (2), the cylindrical auxiliary electrode (3), and an electrolyte (e.g., KCl) solution (4). The internal solution is separated by the polymer... 

H.J. Forman and I. Fridovich, Electrolytic univalent reduction of oxygen in aqueous solution demonstrated with superoxide dismutase. Science. 175, 339 (1972). 

The mechanism of cathodic luminescence is distinctly different from other ECL systems. Light is emitted from oxide-covered, so-called valve metal, electrodes, namely aluminium and tantalum, during the reduction of peroxodisulfate, hydrogen peroxide, or oxygen, in aqueous solution, at relatively low potentials (<10 V). The mechanism involving persulfate, for example, is as follows. A conduc-... 

Lewis, R. S., and W. M. Deen, Kinetics of the Reaction of Nitric Oxide with Oxygen in Aqueous Solutions, Chem. Res. Toxicol., 7, 568-574 (1994). 

Next we considered the oxide ion electrode, and we were a little fearful of this one. There had been some work done in sulfates, and several hundred degrees warmer than this, in which there was some question as to whether or not the oxygen electrode was really acting reversibly on platinum. Furthermore, studies by Yeager and others have shown that whenever one uses oxygen in aqueous solution at electrodes there is a tendency to equilibrate with peroxide rather than with oxide or hydroxide. We were afraid that we might end up with some one-electron transfer reactions and get peroxide ions and the like but we had to try it because the other electrode just wouldn t work. As it turned out, it worked very nicely. 

The presence of dissolved oxygen in aqueous solution was reported to play a very important role in the generation of highly oxidative hydroxyl free radicals therefore, the free-radical attack in both gaseous and film regions is strongly influenced by the dissolved gas presented in aqueous solutions. Under uncontrolled conditions, the temperature of solution might... 

Oxidation of DMS to DMSO and DMSO. DMS is chemically and biochemically oxidized to dimethylsulfoxide (DMSO). Mechanisms for the in situ oxidation of DMS to DMSO in seawater have received little attention, even though this may be an important sink for DMS. Hydrogen peroxide occurs in surface oceanic waters (22) and is produced by marine algae (98). It may participate in a chemical oxidation of DMS, since peroxide oxidizes sulfides to sulfoxides (991. Photochemical oxidation of DMS to DMSO occurs in the atmosphere and DMSO is found in rain from marine regions (681. DMS is also photo-oxygenated in aqueous solution to DMSO if a photosensitizer is present natural compounds in coastal seawater catalyzed photo-oxidation at rates which may be similar to those at which DMS escapes from seawater into the atmosphere (1001. 

In order to calculate the standard transformed Gibbs energies of formation of the four oxygenated forms of hemoglobin, we need the value of AfG° for molecular oxygen in aqueous solution at 21.5°C. The NBS Table (1992) indicates that ArG0(O2(ao)) = 16.1 kJ mol-1 at 21.5°C. The value of ArG 0(T(O2)) is calculated using... 

Tolk, A., Lingerak, W. A., Kout, A., Boerger, D. Determination of traces of hydrogen, nitrogen and oxygen in aqueous solutions by gas chromatography. Anal. Chim. 

Kurimura et al. (22) studied the oxidation of Fe +(EDTA) and Fe +(NTA) by dissolved oxygen in aqueous solutions and suggested that the oxidation proceeds by two parallel reaction paths, with both pro-tonated and unprotonated chelates reacting. The reaction mechanisms suggested (22,23) are as follows ... 

Oxygen transfer is an important issue in the operation of a hollow-fiber bioreactor. In these bioreactors, a membrane-based aeration system is usually included in the intracapillary recirculation loop to enrich the recirculating culture medium with oxygen. However, due to the low solubility of oxygen in aqueous solutions, the recirculation speed through the fibers must be very high. 

A complete removal of oxygen in aqueous solution is not feasible and thus in practice, the metal ions are frequently complexed with chelating agents (EDTA, disodium edate, citric acid, etc.). 

Resistance at the gas-liquid interface This resistance is often ratecontrolling in aerobic fermenters because of the relatively low solubility of oxygen in aqueous solutions and the absorption inhibition effects of absorbed materials at the interface. 

Co(his)2] combined reversibly with dioxygen in aqueous solution. This was an important result, for [Co(his)2] was the first synthetic compound to undergo reversible oxygenation in aqueous solution and it was evident that oxygenation was a general rather than an isolated phenomenon. This early chemistry of cobalt-dioxygen complexes has been reviewed.630,633- 5... 

Fang X, Pan X, Rahmann A, Schuchmann H-P, Sonntag C von (1995) Reversibility in the Reaction of Cyclohexadienyl Radicals with Oxygen in Aqueous Solution, Chem. Europ. J. 1, No. 7 423-429. 

Indicates that I" can be oxidized by oxygen in aqueous solution. 

The dicobalt complex of the cryptand ligand O-BISTREN (18) displays reversible oxygenation in aqueous solution, with the maximum concentration of the oxygenated species being observed over the pH range 7.8 to 8.8. Purging... 

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