Oxides oxygen

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

There is no evidence for the existence of thallic hydroxide addition of hydroxide to an aqueous solution of a T1(III) salt gives TI2O2 instead. ThaHous hydroxide can be isolated as yellow needles by the hydrolysis of thaHous ethoxide [20398-06-5] which is conveniendy prepared as a heavy oH by the oxygen oxidation of thallium metal in ethanol vapor. ThaHous hydroxide darkens at room temperature and decomposes to TI2O and H2O on warming. 

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

Silica gel and aluminium oxide layers are highly active stationary phases with large surface areas which can, for example, — on heating — directly dehydrate, degrade and, in the presence of oxygen, oxidize substances in the layer This effect is brought about by acidic silanol groups [93] or is based on the adsorption forces (proton acceptor or donor effects, dipole interactions etc) The traces of iron in the adsorbent can also catalyze some reactions In the case of testosterone and other d -3-ketosteroids stable and quantifiable fluorescent products are formed on layers of basic aluminium oxide [176,195]... 

Oxygen (oxide ions) in crystal lattices can be progressively removed by systematically... 

The main route to produce acrolein is through the catalyzed air or oxygen oxidation of propylene. 

There is a reaction between beryllium and nitrogen that starts at about 750°C and is appreciable at 850°C, beryllium nitride being formed". The reaction with oxygen is less sluggish and at 900°C in oxygen oxidation proceeds at about twice the rate of nitride formation. Thus when beryllium is heated in air, beryllium nitride forms only a small proportion of the total scale —about 0-75% after 1 h at 1 000°C. 

Sometimes, though, it is by no means obvious how a given half-equation is to be balanced. This commonly happens when elements other than those being oxidized or reduced take part in the reaction. Most often, these elements are oxygen (oxid. no. = — 2) and hydrogen (oxid. no. = +1). Consider, for example, the half-equation for the reduction of the permanganate ion,... 

Let s look in more detail at the processes. A drop of water on the surface of iron can act as the electrolyte for corrosion in a tiny electrochemical cell (Fig. 12.18). At the edge of the drop, dissolved oxygen oxidizes the iron in the process... 

It was observed leldivdy early that chonically labile compounds - such as vitamins, carotenes - decomixise, either on application to the TLC layer or during the TLC separation that follows. Ibis phenomenon was primarily ascribed to the presence of oxygen (oxidation) and exposure to light (photochemical reaction) in the presence of the active sorbents, which were assumed to exert a catalytic effect (photocatalytic reaction). 

Journal of Applied Polymer Science 70, No.l, 3rd Oct. 1998, p. 129-35 CHEMICAL RECYCLING OF FLEXIBLE PVC BY OXYGEN OXIDATION IN NAOH SOLUTIONS AT ELEVATED TEMPERATURES Yoshioka T Furukawa K Sato T Okuwaki A Tohoku,University... 

A second separation technique is leaching, which uses solubility properties to separate the components of an ore. For example, modem gold production depends on the extraction of tiny particles of gold from gold-bearing rock deposits. After the rock is crushed, it is treated with an aerated aqueous basic solution of sodium cyanide. Molecular oxygen oxidizes the metal, which forms a soluble coordination complex with the cyanide anion ... 

Stratton, S.P., Schaefer, W.H., and Liebler, D.C., Isolation and identification of singlet oxygen oxidation products of beta-carotene, Ghent. Res. Toxicol, 6, 542, 1993. 

Similar experiments on a-oxygen oxidation were also carried out with ethane resulting in a selective formation of ethanol. 

Figure 6. Thermogravimetric analysis (TGA) of free 55 K PVP and 7.1 nm Pt-PVP nanoparticles in oxygen. Oxidative decomposition of free PVP begins at 573K, while significant weight loss due to the catalyzed oxidation of PVP on PVP-protected Pt nanoparticles occurs at 473 K. It appears that PVP layer is not a complete monolayer or the entanglement of PVP chains causes a porous polymer layer enabling oxygen diffusion to the nanoparticle surface [17]. (Reprinted from Ref [17], 2006, with permission from Springer.)...

The allylic hydroperoxides generated by singlet oxygen oxidation are normally reduced to the corresponding allylic alcohol. The net synthetic transformation is then formation of an allylic alcohol with transposition of the double bond. 

The reactivity order of alkenes is that expected for attack by an electrophilic reagent. Reactivity increases with the number of alkyl substituents.163 Terminal alkenes are relatively inert. The reaction has a low AHl and relative reactivity is dominated by entropic factors.164 Steric effects govern the direction of approach of the oxygen, so the hydroperoxy group is usually introduced on the less hindered face of the double bond. A key mechanistic issue in singlet oxygen oxidations is whether it is a concerted process or involves an intermediate formulated as a pcrcpoxide. Most of the available evidence points to the perepoxide mechanism.165... 

Atomic oxygen oxidation of polymers has been reported by a few authors (46,50). Experiments were limited to the measurements of weight-loss data and changing of the wetteability (46-48), and only two papers were devoted to the study mechanism of atomic oxygen oxidation of polydienes (49,50). 

The PP samples exposed to atomic oxygen show for the formation of polymer peroxy radicals (P00 ), which give almost identical ESR spectrum as in the case of ozone reaction (Fig.l). The ESCA spectra (Fig.5) indicate that atomic oxygen oxidation is more effective than ozonization. These results support our assumption that ozonization... 

Slow reaction which also occur during photo-oxidation and/or thermal oxidation can take place during oxidation with atomic oxygen, but these slow reactions are of little importance because of the rapid oxidation which usually occurs. More results which explain atomic oxygen oxidation mechanism of PP, will be published separately. 

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