Determining rate parameters

Rate-Determining Parameters of a Sequence of Monomolecular Reactions... 

Rate-Limiting Steps, Rate-Determining Parameters, and Apparent Activation Energy of Simpie Schemes of Chemicai Transformations... 

Let us find the rate-determining parameters for a simple stepwise bimolecular reaction just discussed (see equations (1.38) (1.39)) ... 

Again, while the stationary rate of stepwise noncatalytic reactions is independent of the standard thermodynamic parameters of thermafized intermediates, the rate determining parameters of catalytic reactions may depend on the standard thermodynamic parameters of thermafized catalytic intermediates and, as a consequence, influence considerably the apparent activation energy of the overall process. 

Let us identify the rate-determining parameters of the stationary catalytic transformation of substance R to substance P... 

Thus, the rate-determining parameters here are the standard Gibbs energy of the formation of the transition state in elementary reaction 1 (scheme 4.4) and the standard Gibbs potentials of the formation of "external" reactants R as well as of P and intermediate Ki. The apparent activation energy of the stepwise reaction is... 

In catalytic stepwise reactions, which involve more complex elementary transformations than scheme (4.4), the rate-determining parameters can be identified through similar considerations. Several examples of simple model schemes of catalytic transformations are given following. These schemes often are used for the microkinetic analysis of particular catalytic transformations and help to reveal the influence of various factors. 

Therefore, the rate-determining parameters here are the standard Gibbs potentials of the formation of thermalized intermediate Ki and of the transition state of the rate-limiting... 

While identifying the rate determining parameters of the catalytic trans formation schemes under consideration, we understand better the reason for possible energy correlations in catalysis, the Broensted Polanyi relations for the transition state energies of surface transformations being typically apphed. Such an approach was intensively used in 1960s—1970s to... 

The first explanation offered for the phenomenon of dispersive kinetics is that it is caused by a distribution of rates of primary electron transfer, and that the islowi P lifetimes originate from a minority of reaction centres from the islowi tail of this distribution. The energetic basis for this distribution could be an inhomogeneous distribution of a rate-determining parameter such as X, AG or Vda (or any combination of these) (Figure lOA). The principal alternative explanation is that the multiple lifetimes represent a time-dependent energetic relaxation of the P Ha intermediate due... 

Degradation Type Main Rate Determining Parameters... 

---