Eyring-type analysis

The analysis of the curvature of the experimental parabola led to very reasonable determinations of the intrinsic barrier. The measured values are relatively large, ca. 10-13 kcal moP, i.e. larger than usually found in stepwise dissociative processes but still not as large as found with other dissociative-type acceptors, such as halides. On the other hand, if the intrinsic barriers are calculated by the Eyring equation (equation 4) the values are larger by a few kcal mol (using the collision frequency factor Z). This is because the heterogeneous ET is actually non-adiabatic (which means that the actual pre-exponential factor is smaller). This is a very important aspect, which will be covered below. 

The VB simplified model of ground-state potential energy surface H3 system considered as transition state and stabilization valleys of the H + H2 reaction is also an early problem, belonging to the history of physical chemistry under the name London-Eyring-Polanyi-Sato (LEPS) model that continues to serve as basis of further related developments [17,18], The actual analysis is a new a focus on the JT point of this potential energy surface able to absorb results of further renewed CASCCF type calculations on this important system. 

In a report describing acid-promoted Ritter reactions involving a-methylene-)5-hydroxyesters, an I -type process was found to be the preferred mechanism. For compound (104), both Ritter reaction products (105 and 106) are obtained. In order to rule out 5 2 or Sf 2 mechanisms, kinetic analysis was performed, kinetic isotope effects were evaluated, and both Hammett and Eyring plots were done. The mechanistic studies were consistent with an I -type process being preferred with initial formation of the oxonium cation, loss of water, and formation of the allylic acarbocation (107). DFT calculations indicated nucleophilic attack at the terminal carbon (107b, 5 10 was favored by about 2.6kcalmol over attack at the benzylic position (107a, 5 1) (Scheme 23). 

---