Activation energies obtainable

Initial protonation of iron in protodesilylation of trimethylsilylferrocene was not, however, favoured as a mechanism by Marr and Webster689, who measured rates by the spectroscopic method using hydrochloric acid in 20 vol. % aqueous methanol (Table 235) and found that the rate of desilylation of the ferrocene compound was little more than that for the 4-methoxyphenyl and 2,4-dimethyl compounds. The similarity of the spread of rates in the different media and the similar activation energies and entropies were considered as evidence that the transition states for reaction of all three compounds were similar. The lower activation energy obtained for the 4-methoxyphenyl relative to the ferrocene compound may arise from the different media involved the difference in entropy seems, however, to be rather larger than one might have expected even allowing for the solvent differences. 

The corresponding overall activation energy obtained was 33 kcal.mole . At 100 °C, the measured half-time for exchange was 13 min. 

The rate was found to be unaffected by light and either [Cl"] or [CIO4 ]. The overall activation energy obtained was 33.4 kcal.mole". The mechanism of exchange suggested by Rona was... 

The apparent activation energy obtained from the slope of a plot of the logarithm of the rate Rp of pol merization against /T will be related to the individual activation energies, in analogy with Eq. (19), as follows ... 

Rotators in the solid state experience a well defined potential, with a depth and symmetry resulting from interactions with surrounding ions or molecules. Combined translation and rotation of CD4 lead to a much less specified meaning of the apparent activation energy obtained experimentally. Obtained values indicate that we have different values of the activation energy for different temperature ranges. Therefore their relation to local potentials at the walls of cages requires a further study. 

In the absence of nucleophiles thermal decomposition of 5-t-butyl and 5-isopropyl-1,3,4-dioxazol-2-ones follow first-order kinetics with activation energies, obtained from Arrhenius plots, ranging... 

Some interesting work on the decomposition kinetics of IC(N02)3 has been reported. In the gas phase this compd decomposes with homogeneous first order kinetics over the temp range of 100-160° (Ref 6). The activation energy obtained (E = 34.4 kcal/mole, log Z = 15.25) suggests that the primary step is the rupture of the C—N bond followed by a radical (nonchain) reaction (Ref 7). Addn of a large excess of NO, one of the decompn products, increased reaction rate 20-30%, addn of a large excess of N02, another decompn product, lowered the reaction rate 10%. Addn of I2, also a decompn product, had no effect on rate (Ref 7)... 

The activation energy E associated with the peak at T = 150K has been calculated by the preceding method, i.e., plotting log I against HE from the initial rise of the curves. Such a plot for Vt = 0.08 K/s is shown in Fig. 2.4. The activation energy obtained by this method is 0.22 eV. 

The relaxation results (1) for the LP sample can be summarized. Line-shape measurements indicated that motional narrowing started at around 60°C, and by 110°C, the lines appeared completely Lorentzian. The activation energy obtained from T2 above 120°C was 16.3 1.2 kcal/mol. 

Additional evidence for the applicability of the above data interpretation is obtained by using Equation 3 to predict values of l/(Tlp) min. These are 2.8 X 104 sec-1 and 6.4 X 103 sec-1 for H = 4.7 G and 20.6 G, respectively, and are consistent with the T p and T2 data. The motional properties reported here differ significantly from previous measurements the activation energy obtained from a temperature above 120°C is two to three times the values obtained in Ref. 13, and motional narrowing of the lineshape occurs at a significantly higher temperature than that in Ref. 12. 

In view of the linearity of the curves presented in Figure 8 and the high activation energies obtained by using Equation 1 at constant values of there seems to be considerable justification for the chemisorption model of volatile matter release. The fact that the initial rates of H2 release show a zero-order dependency may be attributed to the fact that for raw anthracite the fraction of surface coverage is practically unity. Under these conditions, where almost all of the sites available for H2 adsorption are filled, Equation 1 leads to the result that the rate of change of coverage with respect to time is initially constant. 

Rate Constants and Activation Energies obtained by Elias... 

Let Ep denote the apparent activation energy obtained from the slope of the graph of In kx vs. 1/T. If E is not temperature independent, then... 

It appears from these results that the activation energies obtained are higher than those reported for the reduction process proper (about 20... 

For the carbonate group, the activation energy obtained in the bulk cannot be compared to that determined for DPC as it does not concern the same rotation. In the latter case, calculations refer to a rotation around the OfOff axis,... 

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