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Catalysis Reactions Either Increase or Decrease Reaction Rates

Catalysis reactions are those that either cause the increase or the decrease in the chemical reaction rate. They do this by means of a chemical substance known as a catalyst. A catalyst is much different from other types of reagents because it does not get consumed when participating in the reaction itself. Other reagents that take part in chemical reactions are most often consumed through the process. These catalysts may take part in many different chemical transformations. When catalysis reactions are sped up in regards to the catalyst, they are called a positive catalyst. On the other side of the equation, the catalysts that assist in the slowing down of a chemical reaction is known as a negative catalyst, inhibitors or catalytic poisons. In the catalysis reactions such as in the reduction of ethyne to ethane, the catalyst is palladium, with lead(II) acetate. Palladium is known as a partly poisoned or semi negative catalyst. Without the deactivation of the catalyst, the ethane that is produced will be further reduced to ethane.

The basic rule of catalysis reactions is that they have a lower rate-limiting free energy change to the transition state then as do the corresponding in catalyzed reaction. This most often results in a larger rate when done at the same temperature. The mechanism origin of catalysis reactions is a very complex one. These catalysts can affect the reaction environment favorably. One good example of this is acids in catalysts for reactions of carbonyl compounds can form intermediates that are not normally made. Osmate ester in osmium tetroxide-catalyzed dihydroxylation of alkenes, lysis of reagents to reactive forms like hydrogen in catalytic hydrogenation.

In kinetics, catalysis reactions act just like typical chemical reactions. The reaction rate depends on the number of times the contact between the reactants in the rate-determining step. Most of the time the catalyst takes part in this slow step, and the rates are limited by the volume of catalyst used. The diffusion of reagents to the surface and diffusion of products from the surface can be rate determining in heterogeneous catalysis reactions. Analogous events with substrate and product detachment directly apply to homogeneous catalysis reactions. Even though the catalysts are not directly consumed in the catalysis reaction itself, they may be inhibited, deactivated or even destroyed in the secondary processes. In  heterogeneous catalysis reactions, a common type of secondary reaction is called coking. This is where the catalyst may become covered by polymeric side products. Also these catalysts can dissolve right into the solution in a solid-liquid system. They can also completely evaporate in a solid-gas system.

In the production of the majority of industrially important chemicals will involve catalysis. In most biochemically significant processes they are catalysed. The research that is done in regards to catalysis reactions is done so in the applied science category. This involves many areas of chemistry with the most popular being organometalic chemistry and materials science. All catalysts are very important in many areas of environmental sciences as well. A good example of this type of catalysis reaction would be the catalytic converter in automobiles and the over all dynamics of the ozone hole.