Chemical bonds, classification

Table 4-1- Chemical bonds classification by electronic structure and properties [11].

TABLE 13-20 Hydrogen Bonding Classification of Chemical Families... 

Binders improve the strength of compacts through increased plastic deformation or chemical bonding. They may be classified as matrix type, film type, and chemical. Komarek [Chem. Eng., 74(25), 154 (1967)] provides a classification of binders and lubricants used in the tableting of various materials. 

Enzymes catalyzing the hydrolysis of esters are termed esterases. They belong to a larger group of enzymes termed hydrolases, which can cleave a variety of chemical bonds by hydrolytic attack. In the classification of hydrolases of the International Union of Biochemistry (lUB), the following categories are recognized ... 

Thus, as of today, there is no reliable classification of various types of adsorption. Presumably, it would be most correct to consider various types of adsorption interactions consistent with classification of chemical bonds [19]. 

Silvi B, Savin A (1994) Classification of chemical bonds based on topological analysis of electron localization functions. Nature 371 683... 

Sanderson, R. T. 1951. An interpretation of bond lengths and classification of bonds. Science 114 670-672 1976. Chemical Bonds and Bond Energy, 2nd edn. New York Academic Press. 

The value of the density at the critical point pb, the values of the curvature, and the asymmetry of the curvature provide the information for a density-based classification of chemical bonding. Several parameters are used to classify a bond ... 

The adsorption of saturated hydrocarbons on metallic substrates is typically considered as an example of a weak physical interaction, which is dominated by van der Waals forces. The classification of this type of interaction, denoted physisorption where no direct chemical bonds are formed between the adsorbate and substrate, has been based on the heat of adsorption. A physisorbed state is considered to be one in which the heat of adsorption is comparable to the heat of vaporization or... 

It is convenient to consider three general extreme types of chemical bonds electrostatic bonds, covalent bonds, and metallic bonds. This classification is not a rigorous one for, although the bonds of each extreme... 

For the chemist, there is no doubt whatsoever that the softness of the central atoms do not follow the a values, though this is valid for the halides. Thus, Cs(I) is more polarizable than Ag(I), Ba(II) more than Cd(II) and La(III) more than In(III) in disagreement with Pearson s classification. Said in other words, the chemical bonding involves far stronger perturbations than the linear electric fields inducing the a-polarizability. 

Edible oils and fats come under the biochemical classification of lipids owing to their insolubility in water. They are composed of two chemically bonded components, a fatty acid and glycerol there are many different fatty acids. When fats and oils are digested in the body, the fatty acids are liberated. Fatty acids are vital in the diet to act as starting materials for cell structures, for other important bodily chemicals including hormones and as an energy source. 

The term chemisorption was coined in order to classify the interaction between a particle in the gas phase and a solid surface, i.e. the result of the adsorption process [1]. If the interaction leads to the formation of a chemical bond the adsorbate formed is called a chem-isorbate. Where chemical bond formation is not important the process is classified as physisorption. There are several conceptual problems with such a differentiation which we briefly address in the following, and which indicate that a more detailed look at the entire process of adsorbate formation is needed before a reliable classification may be carried out. In fact, as it turns out, for a conclusive classification one would need the full theoretical and experimental understanding of the system under investigation. Such an approach must include the static aspects, i.e. the energies involved, as well as the dynamic aspects, i.e. the processes involved in the formation of the adsorptive interactions. 

The chemist is accustomed to think of the chemical bond from the valence-bond approach of Pauling (7)05), for this approach enables construction of simple models with which to develop a chemical intuition for a variety of complex materials. However, this approach is necessarily qualitative in character so that at best it can serve only as a useful device for the correlation and classification of materials. Therefore the theoretical context for the present discussion is the Hund (290)-Mulliken (4f>7) molecular-orbital approach. Nevertheless an important restriction to the application of this approach must be emphasized at the start viz. an apparently sharp breakdown of the collective-electron assumption for interatomic separations greater than some critical distance, R(. In order to illustrate the theoretical basis for this breakdown, several calculations will be considered, the first being those for the hydrogen molecule. 

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