Reaction kinetics, phase space theory

In contrast to the results obtained for dehydrogenation reactions, kinetic energy release distributions for alkane elimination processes can usually be fit with phase space theory. Results for the loss of methane from reaction 9 of Co + with isobutane are shown in Figure 10b. In fitting the... 

The success of the phase space theory in fitting kinetic energy release distributions for exothermic reactions which involve no barrier for the reverse reaction have led to the use of this analysis as a tool for deriving invaluable thermochemical data from endothermic reactions. This is an important addition to the studies of endothermic reactions described above. As an example of these studies, consider the decarbonylation reaction 11 of Co+ with acetone which leads to the formation of the... 

Statistical methods represent a background for, e.g., the theory of the activated complex (239), the RRKM theory of unimolecular decay (240), the quasi-equilibrium theory of mass spectra (241), and the phase space theory of reaction kinetics (242). These theories yield results in terms of the total reaction cross-sections or detailed macroscopic rate constants. The RRKM and the phase space theory can be obtained as special cases of the single adiabatic channel model (SACM) developed by Quack and Troe (243). The SACM of unimolecular decay provides information on the distribution of the relative kinetic energy of the products released as well as on their angular distributions. 

In accordance with the considerations outlined in the previous section, a statistical kinetic energy release distribution should be observed for this system. As shown in Figure 7, the experimental distribution for this process can be fit very closely using statistical phase space theory, which yields a bond dissociation energy Do°(Fe -C5H5) = 55 + 5 kcal/mol. A reaction coordinate diagram for... 

The remarkably complicated kinetic behavior of reaction (viii) is reviewed in Section 4.5.1 and phase-space theory cannot begin to provide... 

J. C. Light and J. Lin, Phase-space theory of chemical kinetics.II. Ion-molecule reactions,... 

A central problem in studying ion-molecule reactions is the dependence of the microscopic cross-section, a or the rate constant k upon the relative velocity of the ion and the molecule. Only from reliable, established data on this dependence can one choose among the various theoretical models advanced to account for the kinetics of these processes such as the polarization theory of Gioumousis and Stevenson (10) or the more recent phase-space treatment of Light (26). 

N. De Leon, M. A. Mehta, and R. Q. Topper, Cylindrical manifolds in phase space as mediators of chemical reaction dynamics and kinetics. I. Theory, J. Chem. Phys. 94, 8310 (1991). 

Recently, Truhlar [79] has carried out a quantum mechanical statistical phase space calculation to obtain the cross-sections for the same reaction as a function of the initial vibrational state of II2 and the relative kinetic energy of reactants. The results predict enhancement of cross-section by vibrational energy of the reagent, but the agreement with experimental observations is again only qualitative. The experimentally observed enhancement is much greater than that predicted by the theory. 

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