Search results
Results From The WOW.Com Content Network
The activated complex is an arrangement of atoms in an arbitrary region near the saddle point of a potential energy surface. [1] The region represents not one defined state, but a range of unstable configurations that a collection of atoms pass through between the reactants and products of a reaction.
Rates of reaction can be studied by examining activated complexes near the saddle point of a potential energy surface. The details of how these complexes are formed are not important. The saddle point itself is called the transition state. The activated complexes are in a special equilibrium (quasi-equilibrium) with the reactant molecules.
The concept of a transition state has been important in many theories of the rates at which chemical reactions occur. This started with the transition state theory (also referred to as the activated complex theory), developed independently in 1935 by Eyring, Evans and Polanyi, and introduced basic concepts in chemical kinetics that are still used today.
determination of the stereochemistry of products, for example in nucleophilic substitution reactions [8] measurement of the effect of isotopic substitution on the reaction rate [9] for reactions in solution, measurement of the effect of pressure on the reaction rate to determine the volume change on formation of the activated complex [10] [11]
An increase in solvent polarity decreases the rates of reactions where there is less charge in the activated complex in comparison to the starting materials; A change in solvent polarity will have little or no effect on the rates of reaction when there is little or no difference in charge between the reactants and the activated complex. [6]
The equation follows from the transition state theory, also known as activated-complex theory. If one assumes a constant enthalpy of activation and constant entropy of activation, the Eyring equation is similar to the empirical Arrhenius equation , despite the Arrhenius equation being empirical and the Eyring equation based on statistical ...
In chemical kinetics, the entropy of activation of a reaction is one of the two parameters (along with the enthalpy of activation) that are typically obtained from the temperature dependence of a reaction rate constant, when these data are analyzed using the Eyring equation of the transition state theory.
A cyclin-dependent kinase complex (CDKC, cyclin-CDK) is a protein complex formed by the association of an inactive catalytic subunit of a protein kinase, cyclin-dependent kinase (CDK), with a regulatory subunit, cyclin. [1] Once cyclin-dependent kinases bind to cyclin, the formed complex is in an activated state.