Cluster compounds classification

It should be noted that the above classification system of technetium cluster compounds is not the only possible one. In section 4 another classification is described, which is based on thermal stability and the mechanism of thermal decomposition. Section 2.2 is concerned with the classification based on methods of synthesizing cluster compounds. The classifications based on specific properties of clusters do not at all belittle the advantages of the basic structural classification they broaden the field of application of the latter, because for a better understanding and explanation of any chemical, physico-chemical and physical properties it is necessary to deal directly or indirectly with the molecular and/or electronic structures of the clusters. 

Such a classification of technetium cluster compounds, in our opinion, reflects the relationship between the thermal stability and structure of the clusters quite well. Moreover, on the basis of this classification it is easier to follow the mechanism of the main thermochemical transitions of technetium clusters, such as (1) dehydration (2) disproportionation and related processes occurring without changes or with only small changes in mass (3) one-stage processes of thermolysis. We shall now consider these main mechanisms of the thermochemical reactions of technetium clusters in greater detail. 

Assign each compound to its nearest cluster centroid (classification step). 

The biological and physicochemical data relevant to a certain project may be represented as two tables and may be analysed in various ways (see Fig. 22.3). Taking biological or physicochemical data either separately or combined, pattern recognition or classification studies may be useful to detect redundancy in the test systems or classify the compounds in a particular way which may be related to their specific mechanism of action. Clustering and classification of compounds based on their properties is central to molecular similarity smdies. Regression or correlation studies between the biological and chemical data are of... 

I Self-test 10.5) Sketch the 5 orbitals (orbitals that resemble four-lobed d orbitals when viewed along the internuclear axis) that maybe formed by the remaining two d orbitals (and which contribute to bonding in some d-metal cluster compounds). Give their inversion-symmetry classification. 

The preparation of intermediate petrochemical streams requires different processing alternatives depending on the feedstock quality. In our classification of petrochemical feedstocks we closely follow that of Gary and Handwerk (1994) consisting of aromatics, olefins, and parafftn/cyclo-parafftn compounds. The classification of petrochemical feedstocks into these clusters helps to identify the different sources in the refinery that provide suitable feedstock and, therefore, to better recognize areas of synergy between the refinery and petrochemical systems. 

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