Factors Influencing Catalytic Action

Sachtler WMH. 1997. Factors influencing catalytic action—Ensemble and ligand effects in metal catalysis. In Ertl G, Kndzinger H, Weitkamp J, eds. Handbook of Heterogeneous Catalysis. Volume 3. Weinheim VCH-Wiley. 

In catalysis, one of the key concepts to understand catalytic action is the so-called active sites [28], The essential concept behind this term is the fact that catalytic activity in solids is restricted to specific sites in the catalyst surface. Another factor influencing catalytic activity is the geometric factor, that is, a properly spaced array of atoms on the solid surface, named Balandin multiplets,... 

The Haber process involves a synthesis reaction. The two reactants are H2(g) and N2(g), and the products are NH3(g) and heat. The process produces high yields of ammonia by manipulating three factors that influence the reaction— pressure, temperature, and catalytic action. 

The rate of chemical reaction can be changed by varying (1) the rate constant and/or (2) the concentration of reactant. The primary salt effect, or catalytic influence on ionic reactions by simple electrolytes, is brought about by variation of the rate constant term, as was mentioned above according to Bronsted [3]. On the other hand, catalytic influence by polymeric electrolytes was accounted for in terms of change in the substrate concentration by most of the previous authors [la-d]. To our knowledge, it has not been pointed out that the concentration factor is responsible for the catalytic action by simple electrolytes. On the other hand, the polyelectrolyte influence has not been discussed in terms of changes of the rate constant except by us [le]. 

In addition to the freeze-concentration effect, a catalytic role for ice crystals, a favorable orientation of substrate and biocatalyst, the markedly lower dielectric constant of ice compared with water, and the high proton mobility in ice, have been discussed as further factors that possibly influence reactions in frozen systems. In summary, the reverse action of hydrolases provides an attractive alternative to the chemical synthesis of peptides but this approach could also be verified for the synthesis of oligosaccharides and oligonucleotides using glycosidases and ribonu-cleases, respectively11631. 

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