Arrhenius parameters table

This appendix includes a summary of the available MNR relative rate coeflBcients (Table VIII) and Arrhenius parameters (Table IX). In light of the recent demonstration (6) that CgFe F unimolecular complications accompany thermal Reaction 3 at 1.0 kTorr, the quantitative significance of these Arrhenius parameters is uncertain. They are thus only provisionally endorsed pending the availability of new measurements carried out at increased (P/Z). In the present study Table IX has provided the basis for small (kaV s ) adjustments in the neighborhood of 300 K. 

TABLE 8.1 The acidity dependence and Arrhenius parameters for the nitration of some cations in... 

The case of i-methyl-4-quinolone is puzzling. The large proportion of the 3-nitro isomer formed in the nitration (table 10.3 cf. 4-hydroxyquinoline) might be a result of nitration via the free base but this is not substantiated by the acidity dependence of the rate of nitration or by the Arrhenius parameters. From r-methyl-4-quinolone the total yield of nitro-compounds was not high (table ro.3). 

The conclusion that the nitration of quinoline in sulphuric acid takes place via the conjugate acid has been confirmed by Moodie et al.50, who measured the rates of nitration of a wide range of heterocyclic compounds in nitric acid-sulphuric acid mixtures at a range of temperatures. A summary of the second-order rate coefficients and Arrhenius parameters is given in Table 4. From an analysis of the shapes of the plots of log k2 versus sulphuric acid acidity (or some function of this), it was concluded that all of the compounds starred in Table 4... 

Arrhenius parameters for nitration of 4-aikylphenyltrimethyiammonium ions in nitric acid-sulphuric acid mixtures (Table 12). It was argued that the observed Baker-Nathan order of alkyl substituent effect was, in fact, the result of a steric effect superimposed upon an inductive order. However, a number of assumptions were involved in this deduction, and these render the conclusion less reliable than one would like it would be useful to have the thermodynamic parameters for nitration of the methyl substituted compound in particular, in order to compare with the data for the /-butyl compound, though experimental difficulties may preclude this. It would not be surprising if a true Baker-Nathan order were observed because it is observed for all other electrophilic substitutions in this medium1. 

Mason256 has measured the second-order rate coefficients and Arrhenius parameters for the chlorination of benzene, biphenyl, naphthalene, and phe-nanthrene in acetic acid (containing 0.05 % water) and these are given in Table 62. 

Contrary to the results obtained with carbon tetrachloride solvent and entirely in accord with the postulate that the effect arises from the steric hindrance to solvation, the rates of cleavage of ArSnR3 compounds in methanol decrease on increasing the size of the group R. This is shown by the rate coefficients in Table 265, though it is difficult to draw any conclusion from the Arrhenius parameters... 

Only fragmented data are available on polymerization of other methacrylates. Propagation constants and the respective Arrhenius parameters for the homopolymerization of various methacrylates initiated by sodium metallo-organics were reported recently +3,56) and are given in Table 2. 

The stoichiometry of the reduction by Fe(ll) of cumene hydroperoxide is 1 1 (in contrast to reduction of H2O2) but the ratio A[Fe(II)]/A[ROOH] increases greatly in the presence of oxygen. The Arrhenius parameters for reduction of this and related hydroperoxides are quite similar to those of the Fenton reaction (Table 21). The production of acetophenone and ethane in high yield and the simple, second-order kinetics are consistent with the scheme... 

The ability of the stable free radical diphenylpicrylhydrazyl (DPPH) to act as an efficient trap for reactive radicals such as 804 and OH- has been utilised by Bawn and Margerison in their examination of the Ag -S20g couple. The disappearance of the intensely coloured DPPH gave excellent zero-order kinetics the rate as a whole was identical with that found by Fronaeus and Ostman and 2 was given by 3.1 x 10 exp(—17.9x lO /RT) l.mole sec A Sengar and Gupta have also determined Arrhenius parameters for this reduction and have compared them with those for some redox processes (Table 23). 

Table 11. Arrhenius parameters for the spin-state transition in rFet2-nicl.irPF 1. at nr siirpe ...

Table VIII records the Arrhenius parameters and the activity of four alloy films and the two pure metals the results are insufficient to provide a neat correlation with bulk electronic structure such as observed for CO oxidation over Pd-Au wires 129), but the familiar pattern is discernible. The rate of CO oxidation is approximately constant for Ag and Ag-rich films but decreases by a factor of 104 over pure Pd and a Pd-rich film.

Kinetic studies. HERON reactions of 7V-acyloxy-/V-alkoxyamides, which can be conveniently followed by NMR in <74-methanol by monitoring the disappearance of the mutagen or aniline and formation of ester and tetrazene, conform to classical bimolecular kinetics being first order in both mutagen and TV-methyl-aniline.41 43,46,105 Arrhenius parameters and bimolecular rate constants (308 K) for a range of /V- a cy 1 o x y - TV- a 1 k o x y a m i de s 25-30 are collated in Table 5. 

Arrhenius parameters for reactions in the hydrogen-bromine system are shown in Table 3. 

Arrhenius parameters calculated from the data in Tables 1-4 are shown in Table 5. The pre-exponential factors are all within the range expected for uni-molecular decompositions, with the exception of Co2(CO)6C2H2. The low value for its decomposition has been attributed to formation of a CO bridge in the transition state24. 

The Arrhenius parameters and the thermochemical sum of the phenyl-carbon and phenyl-halogen bond dissociation energies are shown in Table 8. The extent of the diphenyl mercury decomposition was determined from the weight of mercury produced. It is the present author s opinion that in calculating the Arrhenius parameters for this compound Carter et al.81 gave too great a statistical... 

Table 41 Isotopic ratios of the Arrhenius parameters for the secondary /3-tritium KIEs in the E2 reactions of p-YC6H4CHTCH2X. ...

Saunders and co-workers (Amin et al., 1990) determined the secondary tritium KIEs for the E2 reactions of [19] with sodium ethoxide in ethanol, [20] with potassium t-butoxide in t-butyl alcohol and [21] with potassium t-butoxide in t-butyl alcohol over a temperature range of 40°C. The Arrhenius parameters were found for each isotopic reactant and the AhIAt ratios were calculated (Table 41). The AH/AT ratios for the reactions of [19] and [21] are both less than unity, confirming that, in agreement with the model calculations, tunnelling is important in these reactions. The AHIAT ratio for the reaction of... 

The Arrhenius parameters for the reaction of the persistent (CF3)2NO-radical with n-Bu3SiH also were determined by ESR spectroscopy (Table V).72 It has been suggested that the unusually low preexponential factor is due to geometric constraints on the transition state. The similar reactivities of (CF3)2NO- and PhCMe200- radicals toward n-Bu3SiH and Ph3SiH, respectively, are expected because both the thermochemistries and spin distributions for these two radicals are rather similar.72,73... 

Table VIII contains rate constants for reactions of tin hydrides with carbon-centered radicals. A striking feature of Table VIII in comparison to other tables in this work is the high percentage of reactions for which Arrhenius parameters were determined by direct LFP or the LFP-clock method. These results are expected to be among the most accurate listed in this work. Scores of radical clocks have been studied with Bu3SnH, but the objectives of those studies were to determine rate constants for the clocks using tin hydride trapping as the calibrated basis reaction.

Table 21 Differential Arrhenius parameters for the competing neighboring-group participation to the unimoplecular H2O loss in the chiral oxonium ions 26 and 28 (A = H)...

Table 22 Arrhenius parameters for the gas-phase racemization and isomerization of chiral ions 35 and 36 Reaction...

Table 23 Arrhenius parameters for the gas-phase intracomplex inversion of O-protonated 1-aryl-l-methoxyethanes...

TABLE 12.2. Arrhenius parameters for the decomposition of catechol and hydroquinone in the presence and absence of iron oxide, assuming pseudo first-order kinetics... 

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