Activation energy and rates

Enthalpies, Activation Energies and Rate Constants of Hydrogen Atom Intramolecular Abstraction in Alcoxyl Radicals (Experimental and Calculated)... 

Enthalpies, Activation Energies, and Rate Constants of Reaction RH + N 02 —> R + HONO Calculated by the IPM Method [168]... 

The IPM as a semiempirical model of an elementary bimolecular reaction appeared to be very useful and efficient in the analysis and calculation of the activation energies for a wide variety of radical abstraction and addition reactions [108-113]. As a result, it became possible to classify diverse radical abstraction reactions and to differentiate in each class the groups of isotypical reactions. Later this conception was applied to the calculations of activation energies and rate constants of bimolecular reactions of chain generation [114]. In the IPM, the radical abstraction reaction, for example,... 

There are not so many data on peroxyl radical reactions with amines. Therefore, the values of activation energy and rate constants of reactions of H02 radical with series of amines were calculated using the IPM model (see Chapter 4). The following parameters were used for calculation [4,26]. 

Similar calculations were performed for the reactions of antioxidants with N02, assuming that the energy of the O—H bond of the formed ONOH is equal to 327.6 kJ mol 1 [111], The parameters used for calculations are summarized in Table 15.17. The calculated values of activation energies and rate constants of the reactions of nitrogen dioxide with antioxidants are given in handbook [4],... 

The activation energies and rate constants for the discussed reactions of the diphenylaminyl radical with various peroxyl radicals calculated in this way are presented below [22]. 

Enthalpies, Activation Energies, and Rate constants of Reactions of Phenoxyl Radicals (A O ) with 2,6-bis(1,1-dimethylethyl)-4-methylphenol (lonol) Calculated by IPM Method, Equations See in Chapter 6, for the Values of a, bre, and A, See Table 18.3... 

The values of calculated activation energies and rate constants of the >NO reactions with chosen phenols and amines are given in Table 18.6. The hydroxylamine formed by the reaction of the nitroxyl radical with InH reacts with peroxyl radicals very rapidly (see Table 18.7). So, two reactions of chain termination occur in oxidized RH in the presence of >NO and InH and chain termination includes the following cycles of reactions. 

On the other hand, if one or both the reactants are solvated, while the activated complex is not, the necessary energy of activation is increased and consequently the rate of reaction is diminished. In case the reactant and activated complex are both solvated, the overall effect on both the activation energy and rate of reaction may be small. 

The overall objective of these studies is to unravel mechanisms of interfacial PT. This requires identification of collective coordinates (or reaction coordinates) and transition pathways of transferring protons. Differences in activation energies and rates of corresponding mechanism due to distinct polymer constituents, acid head groups, side chain lengths, side chain densities, and levels of hydration have to be examined. Comparison with experimental... 

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