Thermodynamic Form of the Rate Transition State Expression

Thermodynamic Form of the Rate Transition State Expression 

Because thermodynamic quantities are commonly expressed in kj mol , we have replaced the Boltzmann constants by the gas constant, R. We calculate the activation energy (in kJ mol ) by applying the definition  

Of course, the converse situation, in which the entropy of the transition state is lower than that of the ground state of the reactant, can also occur (Fig. 3.11). In this case, one speaks of a tight transition state tight, because rotations, vibration or motion of the activated complex are more restricted than in the ground state of the reactant. The dissociation of molecules on a surface provides an example that we shall discuss in the next section. 

The neutral situation, in which the entropy of the transition state does not notably differ from that of the reactant(s) in the ground state yields the standard pre-exponential factor hv = ek T/h which is of the order of 10 s . The influence of the entropy term gives rise to a range of possible pre-exponential factor from about 10  

An example application of transition state theory is to simple gas-phase dissociations of a diatomic molecules such as CO 

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