Oxidizing agents versus

In propellants (see Propellants, Solid in this Vol), some of the work reported by Dunkle (Ref 6) examined the addn of flash reducing agents versus smoke evolved in propint compns for the cal. 50 rifle. The oxides examined included aluminum oxide, stannic oxide, silicon dioxide, ferric oxide and, after proplnt ignition, nickel... 

Ce4+ is a versatile one-electron oxidizing agent (E° = - 1.71 eV in HC10466 capable of oxidizing sulfoxides. Rao and coworkers66 have described the oxidation of dimethyl sulfoxide to dimethyl sulfone by Ce4+ cation in perchloric acid and proposed a SET mechanism. In the first step DMSO rapidly replaces a molecule of water in the coordination sphere of the metal (Ce v has a coordination number of 8). An intramolecular electron transfer leads to the production of a cation which is subsequently converted into sulfone by reaction with water. The formation of radicals was confirmed by polymerization of acrylonitrile added to the medium. We have written a plausible mechanism for the process (Scheme 8), but there is no compelling experimental data concerning the inner versus outer sphere character of the reaction between HzO and the radical cation of DMSO. 

This is the region of the OCP. For an HF electrolyte without an oxidizing agent the electrode is inert, because no chemical reaction occurs at the front (emitter) at this potential range. The OCP depends on illumination condition, substrate doping density, illumination condition, HF concentration and DOC [Otl]. For moderately doped Si substrates in 5% aqueous HF the OCP is usually close to -0.6 V versus SCE in the dark. Under illumination a small negative (cathodic) shift to -0.64 versus SCE is observed for n-type electrodes, while the OCP for p-type substrate shifts significantly in positive (anodic) direction to -0.2 V versus SCE [Be9]. 

Chemical resistance is generally good to limited at room temperature versus dilute bases and weak acids, oils, greases, hydrocarbons, certain chlorinated solvents, cosmetics, aldehydes, some alcohols, ketones, esters, glycols. Polyamides are attacked by organic and mineral acids, oxidizing agents, concentrated bases, phenols. 

Resistance is unsatisfactory versus strong acids, hot oxidizing agents, concentrated bases and phenols. 

An excellent illustration of how the stability of Cu1 relative to Cun may be affected by solvent is provided by acetonitrile. The Cu+ ion is very effectively solvated by MeCN, and the copper(I) halides have relatively high solubilities (e.g., Cul, 35 g/kg MeCN), versus negligible solubilities in H20. Copper(I) is more stable than Cu11 in MeCN and the latter is, in fact, a comparatively powerful oxidizing agent. The tetrahedral ion [Cu(MeCN)4]+ can be isolated in salts with large anions (e.g., CIO4- and PF6 ). 

A recent observation which may lead to an advance in understanding the operation of the bridged versus outer-sphere activated complex is this Cr(dip)s++ (I43) has been shown to react very rapidly with Co(III) complexes, including Co(NH8)e+++ V (dip)s++ reacts much less rapidly with the same Co (III) complexes. In these reactions we are almost certainly concerned with outer-sphere activated complexes. It will thus be possible to compare rates for the two types of mechanisms for a common group of oxidizing agents which can be formed in great variety. 

Based on these results, we assumed that the system possessed some thermal instability, and our strategy was to lower the heat of decomposition of the nitration system Dilution of unstable systems tend to increase their stability Calculation of the heat of decomposition, after dilution with 15 molar equivalents of sulfuric acid (versus 2 3 molar equivalents in the original procedure) shows that the potential for explosive behavior is greatly diminished. This is reasonable since sulfuric acid decomposes endothermically and is not an oxidizing agent. 

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