Oxides of Other Groups

Metal Oxides of Other Groups.—Despite the large number of electrons, some of these have been recently studied. The 90-electron molecule PbO has been studied with a minimal basis set in order to assess the importance of relativistic effects in such calculations.311 Since for Z = 82(Pb) relativistic energies are expected to be large (for the atom, E = 1390 hartree), this molecule is an ideal test case, and comparison with CO, which has the same electronic structure in its valence shell, was carried out. The errors in the calculated De are comparable, and the predicted 

A near-HF calculation of the low-lying states of FeO has also appeared.312 Once again, experimental evidence is ambiguous on the ground-state configuration. Limited Cl calculations were also carried out on various states, and extensive Cl on the lowest 5 2+ state. It was concluded that this state is not the ground state, and at the moment the nature of this state is not completely clear. 

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Pyrolusite is a black, opaque mineral with a metallic luster and is frequendy soft enough to soil the fingers. Most varieties contain several percent water. Pyrolusite is usually a secondary mineral formed by the oxidation of other manganese minerals. Romanechite, a newer name for what was once known as psilomelane [12322-95-1] (now a group name) (7), is an oxide of variable composition, usually containing several percent water. It is a hard, black amorphous material with a dull luster and commonly found ia the massive form. When free of other oxide minerals, romanechite can be identified readily by its superior hardness and lack of crystallinity. 

Although the presence of an N-oxide substituent modifies the reactivity of other groups, only reactions directly involving the Af-oxide part are discussed here. 

The oxidation of other monocarboxylic acids by both Cr(VI) and Mn(VII) is slow. Mare and RoCek examined the effect of COjH groups on the oxidation rates of methine and methylene groups. With a series of dicarboxylic acids... 

Although other less important oxides of the group VA elements are known, only those in which the oxidation states are +3 and +5 are important. When the amount of oxygen is controlled, phosphoms can be oxidized to yield phosphorus(III) oxide. 

The H-phosphonate approach entails phosphitylation of a hydroxylic component with an activated unprotected derivative of phosphonic acid to furnish H-phosphonate (a stable tetra-coordinate form of the unprotected monophosphite) followed by oxidation on phosphorus. The H-phosphonate approach is not generally used for the synthesis of monophosphates due to the difficulty of oxidation of the H-phosphonate monoesters and the necessity either to render the phosphorus atom of H-phosphonate into the three-coordinate form by silylation (to form disilylphosphite) or to introduce a protecting group (to form H-phosphonate diester) prior to oxidation. Nevertheless, in rare cases, the H-phosphonate procedure turns out to be a method of choice if, for instance, the simultaneous oxidation of functional groups other than H-phosphonate is required.51... 

As mentioned in 1.2.1 above, there are several reviews on the properties of RuO as an oxidant in organic chemistry, both as a stoicheiometric but also as a catalytic reagent [12, 34-36, 39, 60, 64, 201-203]. It is one of the most important and versatile of Ru oxidants. In the first few years after its properties in the field were realised it was often used for oxidation of alcohol groups in carbohydrates, but its versatility as an oxidant quickly became apparent and its use was extended to a variety of other reactions, notably to alkene cleavage and, more recently, to the c/x-dihydroxylation and ketohydroxylation of alkenes. 

Oxidation of CHOH groups results, of course, in the formation of carbonyl groups, but the number of aldehyde groups formed is virtually nil. Kaverzneva and others have calculated that for every 100 anhydroglucose rings, 19 CO and 65 COOH groups are formed, but no more than 0.3 aldehyde groups. Such a product is unstable and tends to decompose readily in the presence of moisture or alkalis. 

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