C-H-O systems

The main siUcate iaclusions ia natural diamond are pyroxenes and garnet [12178-41 -5] and the understanding of the conditions of their formation from laboratory studies is the basis for the determination of the P—T conditions when diamond was formed (2—6). CO, CO2, H2, H2O are also found ia diamond (20), and it is possible that diamond nucleated and grew ia a Hquid ia a C—H—O system, perhaps immiscible, but ia equiUbrium with the siUcate matrix (4). Graphite [7440-44-0] is also a common iaclusion ia natural diamond. 

Fig. 3 CSD intermolecular searches on H---0 interactions in (M)C-H---O and [(M)C-H]+- [O]" systems [metal bound C-atoms with M=first row transition metal)...

One can draw the further conclusion that the product concentrations are also functions only of temperature, pressure, and the C/H/O ratio and not the original source of atoms. Thus, for any C—H—O system, the products will be the same i.e., they will be C02, H20, and their dissociated products. The dissociation reactions listed earlier give some of the possible new products. A more complete list would be... 

Although the predominant species forming in the C-H-O system (besides H2O) are methane CH4, carbon dioxide CO2 and its aqueous complexes HCO3 and... 

J. Wamatz. Rate Coefficients in the C/H/O System. Springer-Verlag, 1984. 

In the preceding sections it was seen that the product concentrations are only functions of temperature and pressure and that the original source of the atoms was not important. Thus for a C, H, O system one can specify that the products are COz> H20 and their dissociated products. Some dissociated species have been listed but a more complete product list would include the following ... 

There are other reactions of aromatic compounds, such as metalla-tion reactions, which involve the C-H o-system. 

J. Warnatz, Rate Coefficients in the C/H/O System Combustion Chemistry in Combustion Chemistry, Ed. W.C. Gardiner Jr., Springer-Verlag, New York, 1984, p. 197. 

In many instances diamond synthesis in the C-H-O system is related to diamond formation in nature as discussed in part 2. It was shown that precipitation of diamond can occur in the CO2/CH4 system [38]. No reagent external to the C-H-O system should be required for carbon precipitation while high water fugacities may exist at the site of diamond precipitation. 

A key issue in studies of thermolysis kinetics in hitherto unexplored systems, including Hf-containing polymers, is the optimization of the experimental procedure. Preliminary thermodynamic analysis of the Hf-C-H-0 system offers the possibility of establishing the temperature stability limits of HfC and HfO. Earlier, thermodynamic studies of the Hf-C-H-O system were carried out in relation to hafnium acetylacetonate, which is used to prepare HfC [33]. The most convenient approach to producing hafnium-containing nanocomposites with the aim of... 

A particular success for CSD analysis has been the clear identification of the C-H- 0 interaction as a bond of some importance in stabilizing both large biological structures and the packing arrangements of small molecules. Since then, many studies of weaker interactions, such as 0-H- tt and N-H -TT, and of C-H- -X, where X is N, O or even tt systems,have appeared, and a thorough review of C-H- - -O systems has been presented by Desiraju. ... 

---