Reaction activation barriers

Schroeder J and Troe J 1993 Soivent effects in the dynamics of dissociation, recombination and isomerization reactions Activated Barrier Crossing ed G R Fieming and P Hanggi (Singapore Worid Scientific) p 206... 

In conclusion, for both the insertion and addition reactions of MH2, the reaction enthalpy and the reaction activation barrier correlate with the metallylene s AZ st> pointing to a decrease in the metallylene reactivity as M becomes heavier and when the metallylene is substituted by electronegative substituents which increase AZ st (Table 37). According to these trends, plumbylenes and especially plumbylenes substituted with electronegative... 

Fig. 3. Thermodynamic model of oxide layer as a reaction activation barrier, with free energy release AUoxi

This chapter concerns the energetics of charge-transfer (CT) reactions. We will not discuss subjects dealing with nuclear dynamical effects on CT kinetics. " The more specialized topic of employing the liquid-state theories to calculate the solvation component of the reorganization parameters is not considered here. We concentrate instead on the general procedure of the statistical mechanical analysis of the activation barrier to CT, as well as on its connection to optical spectroscopy. Since the very beginning of ET research, steady-state optical spectroscopy has been the major source of reliable information about the activation barrier and preexponential factor for the ET rate. The main focus in this chapter is therefore on the connection between the statistical analysis of the reaction activation barrier to the steady-state optical band shape. 

Unless the reaction activation barriers are very low, the three chain-growth mechanisms presented here depend upon a relatively high CH2 concentration on the metal surface. Indeed, the rate of the Fischer-Tropsch... 

Guner, V. A. Khuong, K. S. Houk, K. N. Chuma, A. Pulay, P. The performance of the Handy/Cohen functionals, OLYP and 03LYP, for the computation of hydrocarbon pericyclic reaction activation barriers, 7. Phys. Chem. A 2004,108, 2959-2965. 

As a bit more complex model, Li and Balbuena in 2000 investigated Ered of EC and PC (DFT/PCM) [10] by a TD cycle. A potential difference identical to the experimental result referred to Aurbach et al. [35] was obtained. However, the main objective was to investigate an updated two-electron reduction mechanism of EC, following nucleophilic attack from groups at the electrode surface [10]. Here also transition state theory was used to estimate reaction activation barriers, equihbtium constants, and rate constants. The results suggested LijCOs as the favourable product overall, together with lithium diethylene carbonate at high EC concentrations. 

Figure 1.22 Energy differences between averaged catalytic reaction activation barriers leading to major and minor enantiomeric products as a function of the experimentally observed enantioselectivity for AH or ATH of acetophenone catalyzed by 1 and 2 or their derivatives, respectively. RT = 0.59 kcal/mol. (Reprinted with permission from Dub, P. A. et al., Dalton Trans., 45,6756-6781. Copyright 2016 Royal Society of Chemistry.)...

It is obvious for both hydroperoxide and peroxide reaction activation barrier is lower as compared with thermolysis. Hydroperoxide is more active than peroxide. This fact can be explained perhaps by effect of peroxide compounds structure. 

The importance of such direct-clustering effects on reaction has been further demonstrated for charge variation reactions in dipolar media. For such reactions, the dielectric properties of the solvent control the solvation and thus the height of the reaction activation barrier in that solvent. As a result, the reaction rate for such systems is directly correlated with the local dielectric properties of the solvent around the reacting solute. As an example, Johnston and Haynes showed that in SC 1,1-difluoroethane the rate of decomposition of a-chlorobenzyl methyl ether, which has an activated complex that is more polar than the reactant, can be explained by invoking a pressure-dependent effective dielectric constant which exceeds that of the bulk. ... 

In(CH3)3] in Reaction A. Would you expect this to increase or decrease the reaction activation barrier (the energy in the Boltzmann factor for the reaction rate) and how would it affect the total energy change of the reaction (more or less exothermic/endothermic) ... 

---