Structure, chemical binary acids

In terms of chemical structure, Arrhenius acids can be divided into several different subcategories. We rvill look at three of them here binary acids, oxyacids, and organic Objective 4 acids. The binary acids are Q aq), HBr(<3 ), and Yi aqy, all have the... 

To demonstrate the use of binary substructure descriptors and Tanimoto indices for cluster analysis of chemical structures we consider the 20 standard amino acids (Figure 6.3) and characterize each molecular structure by eight binary variables describing presence/absence of eight substructures (Figure 6.4). Note that in most practical applications—for instance, evaluation of results from searches in structure databases—more diverse molecular structures have to be handled and usually several hundred different substructures are considered. Table 6.1 contains the binary substructure descriptors (variables) with value 0 if the substructure is absent and 1 if the substructure is present in the amino acid these numbers form the A-matrix. Binary substructure descriptors have been calculated by the software SubMat (Scsibrany and Varmuza 2004), which requires as input the molecular structures in one file and the substructures in another file, all structures are in Molfile format (Gasteiger and Engel 2003) output is an ASCII file with the binary descriptors. 

When a more acidic oxide is needed, amorphous silica-alumina as weU as meso-porous molecular sieves (MCM-41) are the most common choices. According to quantum chemical calculations, the Bronsted acid sites of binary sihca-alumina are bridged hydroxyl groups (=Si-OH-Al) and water molecules coordinated on a trigonal aluminum atom [63]. Si MAS NMR, TPD-NH3 and pyridine adsorption studies indicate that the surface chemistry of MCM-41 strongly resembles that of an amorphous sihca-alumina however, MCM-41 has a very regular structure [64, 65],... 

In the binary glass-forming systems of alkali metal borates, it is possible to observe change in the trend of a number of physico-chemical properties in the concentration range of approximately 20 mole % of alkali metal oxide. This phenomenon is known in the literature as boric acid anomaly , and it is due to the change in the structure of the B2O3 melt caused by the alkali metal oxide addition and is related to the ability of boron to change its coordination number. 

From the chemical point of view it seems to be of particular interest that further (metastable) tellurium subhalides can be obtained by hydrothermal syntheses in acid solutions. In the hydrothermal work on the crystal growth of arsenic telluro-iodides a pure binary tellurium subiodide with the composition Tcsl was obtained as well as a ternary phase with only small amounts of arsenic (AsT Ij The composition Tejl was checked by chemical as well as energy-dispersive X-ray analysis. Crystals of the new tellurium subiodide are shown in Fig. 43 a crystal structure analysis failed because the quality of the crystals was not suitable for single crystal investigation. During annealing of the subiodide a stable phase combination a-Tel -H Te was formed which indicated the metastable character of TesL... 

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