Basicity of oxides

Basicity of metai oxides. In a given periodic group, basicity of oxides tends to increase as one progresses down the periodic chart (see Table 9.1) For example, in group I1A (2) BeO is amphoteric, but the heavier oxides (MgO,... 

The term [2+2] mechanism is only a formal description of the two-step sequence leading to the osmaoxetane intermediate. For an excellent overview on the theoretical basics of oxidations see J0rgensen, K. A, In Transition Metals for Organic Synthesis-, Beller, M. Bolm, C. (Ed.) Wiley-VCH Weinheim, 1998 Vol. 2, pp. 157. 

Nesterenko, N., Lima, E., Graffin, P., de Menorval, L. C., Lasperas, M., Tichit, D. and Lajula, L. Probing the basicity of oxide surfaces by FTIR spectroscopy of isocyanic acid generated in situ by thermal decomposition of nitromethane. New J. Chem., 1999, 23, 6654)66. 

Lavalley has recently compared the suitability of various IR-probe molecules for the surface basicity of oxides [55] and found that pyrrole (PYH) which would decompose to pyrrolate ions (PY ) over stronger bases is suitable for zeolites [56]. 

Bcrkani ct al. [222] proposed the transformation of an alcohol (cyclopenianol) in the presence of a ketone (cyclohexanone) as a model reaction to characterize the acidity and the basicity of oxide catalysts (Figure 3). Actually, it is a Meerwein-Ponndorf-Verley (MPV) reduction which will be discussed in section 5. The authors found a good correlation between basicity of NaCsX zeolites or K impregnated alumina and their activities for hydrogen transfer (monitored by cyclohexanol or cyclohexene production). On the other hand, the more acidic the catalyst, the higher the dehydration extent. 

Bcrkani, M Lemberton. JL Marezewski, M Perot, G. Transformation of an alcohol in the presence of a ketone as a model reaction to characterize the acidity and the basicity of oxide cataly.sts. Catalysis Letters. 1995 31,405-410. 

The reversibility of such conversion systems was explained by an acido-basic concept which involves 0 anion transfer (Lux-Flood model) and is based ontheacidity or basicity of oxides (Smith scale). All oxides that react reversibly with Li are basic as is the Li20 itself. ... 

Because atoms get larger down a group, metallic behavior (such as ability to form cations and basicity of oxides) inaeases, and this trend becomes especially apparent in Groups 3A(13) to 6A(16). 

Rossi, RR, Busca, G., Lorenzelli, V., Lion, M., and Lavalley, J.C. Characterization of the surface basicity of oxides by means of microcalorimetry and FT-IR spectroscopy of adsorbed hexafluoroisopropanol. J. Catal. 1988, 109, 378-386. 

If the standard error is small on AI ( 0.02 eV), it is certainly high on A because the value of A on surface or at the steady state cannot be ascertained. Moreover, several solids are tried for ODH of alkanes, as already mentioned, with little success as far as selectivity is concerned. For sure, however, the correlations show that a catalyst for ODH must be less acidic than for MOX of alkanes. It must be emphasized that these correlations are given for a theoretical selectivity but do not apply to activity parameters, as far as different reactions are compared. Up to now, and to give an example, our attempts failed in correlating optical basicity of oxides with the turnover frequency measured for various oxidation reactions by using the very thorough work presented by Wachs et al. [92]. 

These reactions are probably assisted by the basicity of oxide ions and the redox properties of Cr, although quantitative discussion has not been attempted. 

In the 1870s textbooks still followed traditional classification or that of the author s own idea. Ivan Dmitrievich Bokii s chemistry textbook Osnovaniia khimii [Foundations of Chemistry], published in 1873-74, for example, classified the elements based on the forms of compounds with hydrogen, equivalent to a classification based on valence. Its second edition was based on the same principles ". Another chemistry textbook (Vvedeniia k izucheniiu khimii [The Introduction to study of chemistry]), published in 1876 by an unknown author, was based on the acidity and basicity of oxide compounds. 

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