catalyst

Management

(noun)

Someone or something that encourages progress or change.

Related Terms

  • viability
Chemistry

(noun)

A substance that increases the rate of a chemical reaction without being consumed in the process.

Related Terms

  • homogeneous mixture
  • concentration
  • activation energy

Examples of catalyst in the following topics:

  • Homogeneous Catalysis

    • However, catalysts do not affect the degree to which a reaction progresses.
    • Homogeneous catalysts are those which exist in the same phase (gas or liquid) as the reactants, while heterogeneous catalysts are not in the same phase as the reactants.
    • Try running the reaction with and without a catalyst to see the effect catalysts have on chemical reactions. 1.
    • Run the model to observe what happens without a catalyst. 2.
    • Run the model again, and observe how the catalyst affects the reaction.
  • Heterogeneous Catalysis

    • Unlike reactants, a catalyst is not consumed as part of the reaction process.
    • The process of speeding up a reaction by using a catalyst is known as catalysis.
    • Homogeneous catalysts are those that occupy the same phase as the reaction mixture (typically liquid or gas), while heterogeneous catalysts occupy a different phase.
    • Generally, heterogeneous catalysts are solid compounds that are added to liquid or gas reaction mixtures.
    • The reason such catalysts are able to speed up a reaction has to do with collision theory.
  • The Effect of a Catalyst

    • Common examples of catalysts include acid catalysts and enzymes.
    • To reiterate, catalysts do not affect the equilibrium state of a reaction.
    • Try running the reaction with and without a catalyst to see the effect catalysts have on chemical reactions. 1.
    • Run the model to observe what happens without a catalyst. 2.
    • Run the model again, and observe how the catalyst affects the reaction.
  • Ziegler-Natta Catalytic Polymerization

    • Ziegler-Natta catalysts are prepared by reacting certain transition metal halides with organometallic reagents such as alkyl aluminum, lithium and zinc reagents.
    • The catalyst formed by reaction of triethylaluminum with titanium tetrachloride has been widely studied, but other metals (e.g.
    • Others have been suggested, with changes to accommodate the heterogeneity or homogeneity of the catalyst.
    • Polymerization of propylene through action of the titanium catalyst gives an isotactic product; whereas, a vanadium based catalyst gives a syndiotactic product.
  • Hydrogenation

    • Catalysts can be divided into two categories: homogeneous or heterogeneous catalysts.
    • Homogeneous catalysts are soluble in the solvent that contains the unsaturated substrate.
    • Often, heterogeneous catalysts are metal-based and are attached to supports based on carbon or oxide.
    • For heterogenous catalysts, the Horiuti-Polanyi mechanism explains how hydrogenation occurs.
    • First, the unsaturated bond binds to the catalyst, followed by H2 dissociation into atomic hydrogen onto the catalyst.
  • Alkylidene Reactions

    • Many structural features of a metathesis catalyst may be changed and adjusted to suit the type of reaction desired.
    • A ROMP catalyst, for example, should complex preferentially with the ring double bond, inducing ring cleavage and formation of a new catalytic site.
    • Much effort has been devoted to creating metathesis catalysts with improved binding and turnover characteristics to fit specific transformations.
    • Schrock's molybdenum catalysts generally show high reactivity, but tend to be air sensitive and intolerant of some functional groups.
    • Tech. ) has produced a family of easily handled ruthenium catalysts that have proven effective and valuable tools in the field of synthetic organic chemistry.
  • Hydrogenation

    • This restriction may be circumvented by the use of a catalyst, as shown in the following diagram.
    • Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product.
    • Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts.
    • First, the alkene must be absorbed on the surface of the catalyst along with some of the hydrogen.
    • Similar complexes have been reported for nickel and palladium, metals which also function as catalysts for alkene hydrogenation.
  • Addition

    • Although it does so less readily than simple alkenes or dienes, benzene adds hydrogen at high pressure in the presence of Pt, Pd or Ni catalysts.
    • Nickel catalysts are often used for this purpose, as noted in the following equations.
    • We have already noted that benzene does not react with chlorine or bromine in the absence of a catalyst and heat.
  • Carbon-Carbon Bond Formation

    • Transition metal catalysts have been applied to many functional group transformations, including hydrogenation (Wilkinson's catalyst), asymmetric epoxidation (Sharpless & Jacobsen catalysts) and asymmetric dihydroxylation (Sharpless catalyst).
    • In the following discussion, however, we shall focus on several new and very useful applications of these catalysts to reactions in which carbon-carbon bonds are formed.
    • Nickel catalysts have been demonstrated to be effective in coupling allylic halides to each other and to various aryl, vinyl and alkyl halides.
    • Because nickel carbonyl is an extremely toxic gas, alternative nickel catalysts have been examined with variable results.
    • The best nickel catalyst was Ni(CO)4, a toxic gas, and recent work by K.P.C.
  • Introduction to Chemical Reactivity

    • Reaction Conditions: The environmental conditions, such as temperature, pressure, catalysts & solvent, under which a reaction progresses optimally.
    • Catalysts are substances that accelerate the rate ( velocity ) of a chemical reaction without themselves being consumed or appearing as part of the reaction product.
    • Catalysts do not change equilibria positions.
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