Calculations oxide

Combustion of alkanes is an example of oxidation-reduction Although It IS possible to calculate oxidation numbers of carbon m organic mole cules It IS more convenient to regard oxidation of an organic substance as an increase m its oxygen content or a decrease m its hydrogen content... 

Notice that this generalization follows naturally from the method of calculating oxidation numbers outlined in Table 2.5. In a C—C bond one electron is assigned to one carbon, the second electron to the other. In a bond between carbon and some other element, none of the electrons in that bond ar e assigned to car bon when the element is more electronegative than carbon both are assigned to carbon when the element is less electronegative than carbon. 

It is too time-consuming to calculate oxidation numbers by drawing electron dot diagrams each... 

Influence of other ions. Two examples are considered to illustrate the importance of other ions in natural waters on Mn(II) oxidation kinetics. In the first example the ionic composition of the solution is typical of that found in freshwaters and in the second example the composition of the solution is typical of that found in the low salinity region of an estuary (I -0.1M). The composition of these solutions is given in Davies (26). The calculated oxidation half-lives based on the model given above for these systems are shown in Table VI. 

In the following sections, oxidation models for calculating oxide thickness and process variables that influence oxidation, as well as oxide structure, are discussed. 

Bond valence sum (BVS) analysis, developed by Brown (43) to calculate metal oxidation states in materials such as high-temperature superconductors and zeolites, has recently been shown by Thorp (44) to be predictive for metalloenzymes and model compounds. On the basis of crystallographic data, the empirical parameters r0 and B are determined. These values can then be used to calculate oxidation states from known coordination environments or coordination numbers from known oxidation states and bond lengths. The requisite equations are... 

The chemistry of difluoramines of the type X—NF has been studied to gain an understanding of the nature of the N—F and N—X bonds, to obtain a picture of the relative electron distributions in X—NFg compounds, and to determine the existence and stabilities of N—F radicals and ions. These compounds have been studied using electrochemistry, com-plexation, infrared spectroscopy, and theoretical calculations. Oxidation-reduction reactions have been carried out, and the effects of various environments on the N—F and N—X bonds have been investigated. The results of these studies emphasize the chemistry of difluoramine and the existence and stability of NFf+, NFg, NFg, and HgNFg+. 

It is too time consuming to calculate oxidation numbers by drawing electron dot diagrams each time. We can speed up the process by learning the following simple rules ... 

The Stock system puts the calculated oxidation number of the metal ion as a Roman numeral in parentheses after the name of the metal. This is the more common convention, although there are cases in which it is difficult to assign oxidation numbers. 

Reactivity patterns in widely varying oxidants are seldom considered, the reduc-tant patterns being more often compared. Such studies can be approached in the same way as that of reductants, but because the [CoCNHjjjX]"" oxidants are so common, there may be more difficulties in determining both the self-exchange rate and reduction potential. Table 1 lists values of and for several oxidants, as well as the calculated oxidation factors (OF) [using (f) in 12.2.5.1.1]. These OF values can be corrected to give effective oxidation (actors, but because fewer reversals of trends appear, the effective oxidation factors are not included here. The OF values suggest a reactivity pattern with a reductant of = 0.3 of [Ru(bipy)3] > [Fe(l,10-phen)3 + > [IrBr ] ",... 

In a closely related paper [121] the calculated oxidation potentials for eight phenolic compounds for which experimental results are known were correlated to develop a calibration curve. From these data the oxidation potentials of coniferyl alcohol, sinapyl alcohol, anisole, guaiacol, and a pinoresinol dimer were predicted. This paper applied B3LYP/6-31G(d) optimizations to both gas phase and solvated models, and compared the results to experimental data at pH = 0. Based on a correlation coefficient of 0.93 for the calibration curve, the oxidation potentials of the nnknowns were determined. The relative results from both of these papers are similar, with dimethoxy compounds having lower oxidation potentials than the mono-methoxy compounds. 

Organic chemists are much more concerned with whether a particular reaction is an oxidation or a reduction of carbon than with determining the precise change in oxidation number. The generalizations described permit reactions to be examined in this way and eliminate the need for calculating oxidation numbers themselves. 

Methods for calculating oxidation numbers in complex molecules are available. They are time-consuming to apply, however, and are rarely used in organic chemistry. 

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