Oxidation autogenous

Selbst-lbschung, /. (of lime) spontaneous slaking. -I dtung,/. autogenic soldering, -oxyda-tion,/. autoxidation, self-oxidation. 

Metal oxide nanocrystals arc mainly prepared by the solvothermal decomposition of organometallic precursors. Solvothermal conditions afford high autogenous pressures inside the scaled autoclave that enable low-boiling solvents to be heated to temperatures well above their boiling points. Thus, reactions can be carried out at elevated temperatures and the products obtained are generally crystalli ne compared to those from other solution-based reactions. 

Oreina leaf beetles (Chrysomelidae, Coleoptera) synthesize cardenolides as part of their defensive secretions that are released from specialized exocrine glands.139,140 Some Oreina beetles sequester and secrete PAs, which are taken directly as N-oxides from their Asteraceae food plants.59 It is assumed that PA acquisition evolved in species that already possessed the ability to synthesize and store cardenolides for efficient defense.14 O. cacaliae is the only species in this family that lost the ability to synthesize cardenolides autogenously. Instead the plant-derived PA A-oxides are stored in the body (primarily in the hemolymph) and... 

Between 140° and 160° C m oxygen and 200° to 270° C. in air oxidation becomes autogenous or self-propellant, and as soon as this point is reached the temperature rises rapidly to the ignition-point.8... 

An alternative preparative method is available in this instance also (see later). The hexafluoroplatinate NF4PtF6 is formed in high yield when PtF6 is treated with a large excess of NF3 and F2 at 125°C under an autogeneous pressure of about 140 atm (65). A less pure sample was obtained by oxidizing a mixture of NF3 and PtF6 with a KrF+ salt (see later). 

Tri-n-butyldifluorophosphorane was first obtained upon interaction between tri-re-butylphosphine and hexafluoro-thioacetone dimer.The method described here involves the reaction of tri-n-butylphosphine sulfide with antimony-(III) fluoride. The method is more generally apphcable in the synthesis of difluorophosphoranes from tertiary phosphine sulfides. The only previously reported difluoro-phosphorane, triphenyldifluorophosphorane, was obtained by the reaction of triphenylphosphine or triphenylphos-phine oxide with sulfur(IV) fluoride under autogenous pressure. ... 

The oxidation of phenol and toluene was performed in a batch reactor at 348 and 353 K, using water and acetonitrile as solvent, respectively with a substrate to H2O2 mole ratio of 3. The oxidation of m-cresol, m-xylene, naphthalene and 2-methylnaphthalene was carried out in a stirred autoclave (Parr instruments, USA) of 300 ml capacity under autogenous pressure. Typically, 1.0 g of the catalyst and 5 g of the substrate in 20 g of acetonitrile/Hj20 (solvent) and appropriate quantity of aqueous H2O2 (26 % by wt.) (substrate to 1 202 of 3 mol) were placed in the reactor. After completion of the reaction (24 h), 25 g of acetone was added to the products, which were then separated from the catalyst by filtration and analysed by GC (HP 5880) using a capillary (cross-linked methylsilicon gum) column and flame ionization detector. TTie identity of some of the products was confirmed by GC-MS (Shimadzu, QP 200 A model). 

Hydrothermal synthesis is one of the important methods for producing fine powders of oxides. A hydrothermal system is usually maintained at a temperature beyond 100 °C and the autogenous pressure of water exceeds the ambient pressure, which is favorable for the crystallization of products. Recent research indicates that the hydrothermal method is also a practical means for preparing chal-cogenide and phosphide nanomaterials, and hydrothermal treatment is an effective method for passivating porous silicons. Similar to hydrothermal synthesis, in a solvothermal process, a non-aqueous solvent, which is sealed in an autoclave and maintained in its superheated state, is the reaction medium, where the reactants and products are prevented effectively from oxidation and volatilization and the reaction and crystallization can be realized simultaneously. Furthermore, organic solvents may be favorable for the dispersion of non-oxide nanocrystallites and may stabilize some metastable phases. 

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