Theory multiplet

Modem State of the Multiplet Theory of Heterogeneous Catalysis A. A. Balandin... 

Balandin A. 1969. Modem state of the multiplet theory of heterogeneous catalysis. Adv Catal 19 1. 

Hammett equation use, 17 92-96 of published data, 17 83-99 soUd catalysts limitations, 17 78-83 Taft equation use, 17 85-92 linear free energy relationships, 29 158-159 multiplet theory of, 19 1-195 of nature of catalyst, 19 159-176 metals, 19 159-161... 

The practice of considering the catalyst as a featureless surface or a planar array of atomic centers deprives theory of an adequate concern for the geometry of the transition from reactants to products. Balandin (23) recognized the importance of the concept of a transition state to the development of a mechanistic theory of catalysis, and in his hands the multiplet theory proved fruitful. However the directional properties of binding orbitals, a subject of more recent development, apparently has not been incorporated into his theory. 

Here the role of the geometrical factors in chemisorption is especially vividly expressed. These factors have been analyzed in detail by A. A. Balandin and co-workers in their papers (see, for example, ref. 18) on the multiplet theory of catalysis, in which they show their prime importance in a number of cases of the catalytic process. The electronic mechanism of chemisorption does not at all exclude these factors, but just stresses their role it retains the geometrical schemes of the multiplet theory but gives them physical content. 

Very important final state effects are those which are described in the final state multiplet theory. They occur in cores containing unsaturated, localized shells (open-shell cores). The theory has been successfully apphed, e.g., in the interpretation of the spectral response from the 4f levels of lanthanides . ... 

As described in the preceding sections, fundamental studies of heterogeneous catalysis at the surface of catalysts are important for understanding reaction pathways and for the development of new or improved catalysts and processes. There have been earlier hypotheses proposed for selective oxidation catalysis for example, the multiplet theory which suggests that the activity depends upon correctly spaced groups (multiplets) of atoms to accommodate the reactant molecule (Balandin, 1969) and electronic theory based on the nature of adsorption on semiconductors and empirical correlations between activity, work function and electrical conductivity (Wolkenstein 1960). The importance... 

The Nature of Reactants. No less effect on z and e is exerted by the nature of the reacting atoms of the molecule. The values of z and e are distinctly different for hydrocarbons, amines, and alcohols (on the same or similar catalysts). This complies with the multiplet theory of catalysis, according to which in the three reactions the following atomic groups, in which the vertical bonds pass over to the horizontal, are in contact with the catalyst ... 

In harmony with the multiplet theory is the observed dependency on the nature of the catalyst, since the atoms of the latter are involved in the multiplet complex. 

The initial collective electronic theory of the fifties, in its simplest form, implied that the electrons and holes-controlled by the bulk structure—of the catalytic solid are available for reactants anywhere on the surface. It largely ignored the geometric factor inherent in Taylor s active site concept or in Balandin s Multiplet Theory. 

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