Oxide stoichiometry

Stoichiometry. Oxidation of alcohols by PCC involves a change of two electrons, rather than the change of three electrons observed in chromic acid oxidations. Under the standard conditions an excels is used, but actually 1 molar equiv. is sufficient for oxidation of 1-octanol (94% yield). 

A third possibility of chemical modification is conversion into an acylsilane which reduces the oxidation potential of the corresponding ketone by approximately 1 V. A peak potential of 1.45 V (relative to Ag/AgCl) for the oxidation of undecanoyltrimethylsilane has been reported. Preparative electrochemical oxidations of acylsilanes proceed in methanol to give the corresponding methyl esters. A two-step oxidation process must be assumed because of the reaction stoichiometry —oxidation of the acylsilane results in the carbonyl radical cation which is meso-lytically cleaved to give the silyl cation and the acyl radical, which is subsequently oxidized to give the acyl cation as ultimate electrophile which reacts with the solvent. A variety of other nucleophiles have been used and a series of carboxylic acid derivatives are available via this pathway (Scheme 49) [198]. 

The semiconducting forms of the transition metal oxides are almost never fully oxidized but often have nearly Daltonide stoichiometry. Oxidation of the metal powder, decomposition of the carbonates, and oxidation of a volatile precursor are all employed. Metal carbonyls, such as Ni(CO)4 and Fe(CO)s, are very useful, since distillation is a facile method of purification for these volatile liquids. Caution Ni(CO)4 is very toxic, and generates CO upon decomposition. 

In this phase of the study emphasis has been placed on several properties which can be directly related to catalytic activity stoichiometry, oxidation state, and dispersion. Since most carbonyl complexes are coordinatively saturated, it is clear that ligands must dissociate to develop active sites. Further, since the adsorption of CO(g) is quite small on the supports and CO is a rather stable molecule, it follows that the development of... 

The synthesis of 2,5-disubstituted oxazoles from methyl ketones and benzylamines in a metal and peroxide-free environment is achieved using l2-promoted domino oxidative cyclization involving C-H bond cleavage and the formation of C-N and C-0 bonds. Slow oxidation of A-acetyl homocysteine thiolactone by iodate to A-acetyl homocysteine thiolacone sulfoxide occurs in a reaction S1 having 1 3 stoichiometry (oxidant reductant). The stoichiometric ratio in excess of 103 (reaction S2) is 2 5 because excess 103 oxidizes the r ion, generated in reaction SI, to I2. The stoichiometry ratio for the I2 oxidation (reaction S3) is 1 1. Complex kinetics are observed because reactions SI, S2 and S3 occur simultaneously with comparable rates. 

Derek W. Smith has suggested qirite appropriately, however [21], that a modem Periodic Table should emphasise relationships among elements having similar (at least superficially) atomic electron configurations, inviting comparisons among stoichiometries/oxidation states/valences/coordination numbers (see JCE, 2005, 82, 1202). H and C are not comparable in this way. ... 

Perfect oxide surfaces are essentially inert to H2 dissociative adsorption, although atomie H may be adsorbed on and diffuse relatively fast in stoichiometrie oxides [96], Oxide layers on metal surfaces impede or prevent the H2 adsorption and H... 

Thin oxide films may be prepared by substrate oxidation or by vapour deposition onto a suitable substrate. An example of the fomrer method is the preparation of silicon oxide thin-films by oxidation of a silicon wafer. In general, however, the thickness and stoichiometry of a film prepared by this method are difficult to control. 

The deposition of titanium oxide thin-films on Mo(l 10) represents a case where the stoichiometry of the film is sensitive to the deposition conditions [4T]. It was found that both Ti02 and Ti203 thin-films could be made. 

Oxidation states can be used to establish the stoichiometry for an equation. Consider the reaction between the manganate(VII) (permanganate) and ethanedioate (oxalate) ions in acidic solution. Under these conditions the MnO faq) ion acts as an oxidising agent and it is reduced to Mn (aq), i.e. 

An additional problem is encountered when the isolated solid is non-stoichiometric. For example, precipitating Mn + as Mn(OH)2, followed by heating to produce the oxide, frequently produces a solid with a stoichiometry of MnO ) where x varies between 1 and 2. In this case the nonstoichiometric product results from the formation of a mixture of several oxides that differ in the oxidation state of manganese. Other nonstoichiometric compounds form as a result of lattice defects in the crystal structure. ... 

Quantitative Calculations The stoichiometry of a redox reaction is given by the conservation of electrons between the oxidizing and reducing agents (see Section 2C) thus... 

This experiment describes the use of FIA for determining the stoichiometry of the Fe +-o-phenanthroline complex using the method of continuous variations and the mole-ratio method. Directions are also provided for determining the stoichiometry of the oxidation of ascorbic acid by dichromate and for determining the rate constant for the reaction at different pH levels and different concentration ratios of the reactants. 

Metal organic decomposition (MOD) is a synthesis technique in which metal-containing organic chemicals react with water in a nonaqueous solvent to produce a metal hydroxide or hydrous oxide, or in special cases, an anhydrous metal oxide (7). MOD techniques can also be used to prepare nonoxide powders (8,9). Powders may require calcination to obtain the desired phase. A major advantage of the MOD method is the control over purity and stoichiometry that can be achieved. Two limitations are atmosphere control (if required) and expense of the chemicals. However, the cost of metal organic chemicals is decreasing with greater use of MOD techniques. 

Octabromodiphenyl Oxide. Octabromodiphenyl oxide [32536-52-0] (OBDPO) is prepared by bromination of diphenyl oxide. The degree of bromination is controlled either through stoichiometry (34) or through control of the reaction kinetics (35). The melting poiat and the composition of the commercial products vary somewhat. OBDPO is used primarily ia ABS resias where it offers a good balance of physical properties. Poor uv stabiUty is the primary drawback and use ia ABS is being supplanted by other brominated flame retardants, primarily TBBPA. 

Butane-Based Fixed-Bed Process Technology. Maleic anhydride is produced by reaction of butane with oxygen using the vanadium phosphoms oxide heterogeneous catalyst discussed earlier. The butane oxidation reaction to produce maleic anhydride is very exothermic. The main reaction by-products are carbon monoxide and carbon dioxide. Stoichiometries and heats of reaction for the three principal reactions are as follows ... 

---