Comparison of rate constants

TABLE 5-2 Kinetic Parameters in 4)3C+SbClj Polymerization of Isobutyl Vinyl Ether in CH2CI2 at O C  

Isopropyl vinyl ether6 ctaC+SbCIg CH2CI2 0 1.1 

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Table 4.8 Comparison of rate constants for a series of Kumada-Corriu coupling reactions in flow reactors with corresponding batch reaction [2],...

Table 3.2. Comparison of Rate Constants for the Photoreduction of Benzophenone...

The methods of co-oxidation and oxidation of hydrocarbon (RiH) in the presence of hydroperoxide (ROOH) opened the way to measure the rate constants of the same peroxyl radical with different hydrocarbons. Both the methods give close results [5,9]. The activity of different secondary peroxyl radicals is very close. It is seen from comparison of rate constants of prim-R02 and, v -R02 reactions with cumene at 348 K [9],... 

Trialkyl phosphites were found to be more reactive to hydroperoxide than aryl phosphites the activation energy depends on a particular phosphite and ranges from 25 to 77 kJ mol-1. At the same time, the reaction depends weakly on the type of hydroperoxide, which can be seen from the comparison of rate constants for the reactions of two hydroperoxides (solvent was PhCl, T=303K [12]). 

Comparison of Rate Constants and Activation Energies of Bimolecular Reactions in Solution and Polymer Matrix... 

Comparison of Rate Constants and Steric Factors of Bimolecular Reactions with Frequency of Reactant Rotation and Orientation in Polymer Matrix (T = 300 K)... 

Comparison of rate constants of reactions in micelles and in non-micellar assemblies... 

Ph0)2P0.0C6H4N02-(4) + OH-, CH2(0H)CH20- CTAC1, CTABr + NaOH, aq.diol. Comparison of rate constants in micelle and solvent Bunton etal., 1983a... 

Table 4. Comparison of rate constants (25 °C) for the reactions of parsley and spinach plastocyanins, pH7.5,1=0.10 M(NaCl) [95, 99, 100]...

Table 10. A comparison of rate constants for intramolecular electron transfer in Ru(NH3)j-modiiied electron transport metalloproteins, modifications at surface histidine present in native proteins, pH 7. Values of AE° by determined measurements on modified protein except as indicated...

IV. COMPARISONS OF RATE CONSTANTS MEASURED IN THE VERY HIGH PRESSURE AND LOWER PRESSURE RANGES... 

The high reactivity of radicals and atoms is clearly seen from the comparison of rate constants of reactions of the same type involving molecules and radicals with a closely related structure. High reactivity is manifested by free atoms and radicals in abstraction reactions. For example, the peroxyl radical abstracts the H atom from cyclohexane with the rate constant... 

Comparison of rate constants for OH and 0 reactions given in Table I and IV is of some interest. 

Comparison of Rate Constants and of Equilibrium Constants for Adduct Formation on Attack of MeO" Ion in MeOH at CH and COMe Positions as Expressed by k /kOMc and KH/KOMe Ratios. Respectively"... 

Richard has also shown that intrinsic barriers for carbocation reactions depend not only on the extent of charge delocalization but to what atoms the charge is delocalized. In a case where values of pifR for calculation of A were not available, comparisons of rate constants for attack of water kH2o with equilibrium constants for nucleophilic reaction with azide ion pKAz for 65-67 showed qualitatively that delocalization to an oxygen atom leads to a lower barrier than to an azido group which is in turn lower than to a methoxyphenyl substituent.226... 

It is not intended to extend this discussion of reactions of carbocations with water to consideration of the alcoholic solvents trifluoroethanol (TFE) and hexa-fluoroisopropanol (HFIP), which have been extensively studied and reviewed by McClelland and Steenken.3 However, an important point of interest of these solvents is that their reactivities toward carbocations are greatly reduced compared with water (by up to a factor of 104 in TFE and 108 in HFIP) and that differences in rate constants can be observed between cations which would react indiscriminately at the solvent relaxation limit in water. The following comparisons of rate constants for carbocations with similar pAR values reacting with hexafluoroiso-propanol241,242 reinforces the conclusion that structural variations in the cation lead to changes in intrinsic barrier and, for example, that phenyl substitution is probably associated with such an increase in going from benzyl to benzhydryl (although the benzyl cation itself is not shown). 

A similar comparison of rate constants for 0.6 and 5% Pt/alumina and 1,8% Ag/alumina catalysts at 673 K in oxygen atmosphere reveals that sintering rates for the Ag catalyst are roughly 40-50 times higher than for either Pt catalyst. Thus, Pt is clearly much more thermally stable than Ag under oxidizing conditions. These results are consistent with those from a model catalyst study [44] of sintering of Pt and Ag on alumina in vacuum in which it was observed that Pt/alumina was thermally stable in vacuum to about 873 K, above which temperature liquid-like particle migration was observed, while Ag/alumina was stable to only 723 K, above which temperature evaporation of the metal was observed. This latter result is... 

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