Variation of rate constant

In all three cases, the variation of rate constant with dielectric constant is such that a plot of In k versus 1/e should be linear. 

Living graph Figure 13.23 Variation of rate constant with , iK temperature... 

The graphical treatment of the variation of rate constants with temperature is appropriate when a set of values is available. When only two values of the rate constant are available, is calculated using... 

Figure 4. The variation of rate constants k(M s 1) at 25 °C (relative scale) for the oxidation of parsley PCu(I) with Fe(CN)63 (A) cind Co(phen)s3 (%), and spinach PCu(I) with Co(phen)/ (if) [I = 0.10 M (NaCl)]. (Reproduced from Ref. 10. Copyright 1978, American Chemical Society.)...

Figure 7. The variation of rate constants k (25 °C) with pH for the reduction of parsley plastocyanin PCu(II) with Ru(NH3)5py2+ (%) and cytochrome c(II) (A)...

Two other general ways of treating micellar kinetic data should be noted. Piszkiewicz (1977) used equations similar to the Hill equation of enzyme kinetics to fit variations of rate constants and surfactant concentration. This treatment differs from that of Menger and Portnoy (1967) in that it emphasizes cooperative effects due to substrate-micelle interactions. These interactions are probably very important at surfactant concentrations close to the cmc because solutes may promote micellization or bind to submicellar aggregates. Thus, eqn (1) and others like it do not fit the data for dilute surfactant, especially when reactants are hydrophobic and can promote micellization. 

The hydroxyethyl quaternary ammonium ion in (20) is a weak acid the pATa-value of the non-micellizing model compound, choline, is 12.8 (Haber-field and Pessin, 1982). Reactions of the alkoxide zwitterion are therefore followed at relatively high pH, and from the variation of rate constant with... 

Variations of first-order rate constants by the hydroxyethyl amphiphile, (C8H17)3 N+CH2CH2OH MsO +NaOH are shown in Fig. 7 for variation of [amphiphile]. The curves are calculated in terms of the distribution of substrate between water and the aggregate. Similar observations were made for reaction with 2,4-dinitrochlorobenzene. The reaction rates depend also on the extent of deprotonation of the hydroxyethyl group (26) and the variation of rate constant with [NaOH] is shown in Fig. 8. The curves are calculated in terms of the binding of the substrate and deprotonation of the hydroxyl group (Biresaw et al., 1984). 

The reason is that these alleged kp values are mostly composite, comprising the rate constants of propagation of uncomplexed Pn+, paired Pn+ (Pn+A ), and Pn+ complexed with monomer or polymer or both, without or with an associated A" [17]. Even when we will eventually have genuine kp values for solvents other than PhN02, it will not be possible to draw many (or any ) very firm conclusions because the only theoretical treatments of the variation of rate constants with solvent polarity for (ion + molecule) reactions are concerned with spherically symmetrical ions, and the charge distribution in the cations of concern to us is anything but spherically symmetrical. 

Fig. 6.5 Skrabal diagram variation of rate constant with pH for acid base catalyzed reaction.

Table 2. Acid dissociation pK values, 1 = 0.10 M(NaCl), relating to the active site protonation of different plastocyanins, PCu(I), as determined by (a) proton NMR (b) the variation of rate constants (25 °C) with pH for the [FelCN) ] oxidation of PCu(I), 1 = 0.10 M(NaCl), and (c) similar experiments with [Co(phen)3] " as oxidant. The latter is an apparent value only, and is believed to be composite due to reaction occurring at the remote site...

Table 9. Acid dissociation pK, values relating to the protonation at the remote binding site of different plasto-cyanins [49, 101] as obtained from the variation of rate constants with pH 25 °C, 1=0.10 M(NaCl)...

Figure 14. Variation of rate constant with x for the second stage of two-stage extraction of coal first stage at 250°C. for 8 hours not shown...

It was generally believed that the characteristic non-linear dependence of the rate constant on n was associated with the existence of the preequilibrium (Bell, 1941). For the mutarotation of glucose a linear variation of rate constant with n had been reported (Hamill and La Mer, 1936c) and cited as an example of a mechanism of acid catalysis without pre-equilibrium. 

Figure 3. Variation of rate constant for cyclohexene hydrogenation, k, with time on stream for deactivated catalysts. Conditions reaction temperature, 175°C and total pressure, 225 psia. Key O, AM-C , NU-A , NU-E , AM-D NU-B A, AM-F and A, NU-F.

The solution kinetics involves three fundamental types of experiment, namely (i) rate law, (ii) stereochemistry and (iii) variation of rate constant with structure or environment. Each one permits the analysis of slightly different aspects of a reaction, and then develops a scheme of reaction classification which throws light on the behaviour of a reaction in each experimental situation. It is useful to briefly discuss the role of each of the three types of experimental investigation in the study of complex substitution reactions. 

Figure 3 shows variation of rate constant with time-on-stream at WHSV of 2.0 hr l. The figure suggests that aging rate constant does not depend on reaction pressure within the range of 3 - 8 kg/cm G. Higher reaction pressure decreased initial rate constant of light naphtha conversion. 

Figure 3. Variation of rate constant of light naphtha conversion with increasing pressure under constant space velocity over the stabilized catalyst.

For [Ru(sar)]2+ 2+ pair, in which on a change in their oxidation states the Ru-N distances (Ar) vary only O.OOSA on average and electronic transition is not forbidden, the maximal value of Log ku was observed. The changes in M-N distance increase in the order Ru < Ni < Mn < Fe < Co. Logkn values decrease with an increasing the Ar values (Fig. 44). The variation of rate constants for electron exchange in these sarcophaginates is expressed by the equation... 

The variation of rate constants with temperature, interpolation and extrapolation... 

Figure 4, Variation of rate constants for the autoxidation of ascorbic acid as a function of concentration of Cu(ll) chelates at 25°C and - log [H ] of 3.45 EDTA = ethylenediaminetetraacetic acid HEDTA = hy-droxyethylethylenediaminetetraacetic acid NT A = nitrilotriacetic acid HIMDA = hydroxyethyliminodiacetic acid IMDA = iminodiacetic acid.

Figure 2. Variation of rate constant with catalyst age...

Figure 5. Simulated Tafel plots [from Eq. (40)] for a reaction involving three consecutive electron-transfer steps, showing the effect of variation of rate constants for (a) intermediate-consuming and (b) intermediate-creating nonrds steps, (a) Rate constants A, = -2 = 10 cm s (i.e., the rds) and k =...

Figure 10 Variation of rate constants for the diffusion step kl (A), penetration step k2 ( ), and rearrangement step k3 ( ) of the adsorption of native and succinylated pea legumin at the air-water interface in dependence on the degree of iV-succinylation. (From Ref. 22.)...

---