Rate constants for second-order reactions

Table 3.1 summarises the influence of the diamine ligands on the equilibrium constant for binding of 3.8c to the ligand-metal ion complex (K ) and the second-order rate constant for reaction of the ternary complex (ICjat) (Scheme 3.5) with diene 3.9. 

Studies of micellar catalysis of himolecular reactions of uncharged substrates have not been frequent" ". Dougherty and Berg performed a detailed analysis of the kinetics of the reaction of 1-fluoro-2,4-dinitrobenzene with aniline in the presence of anionic and nonionic surfactants. Micelles induce increases in the apparent rate constant of this reaction. In contrast, the second-order rate constant for reaction in the micellar pseudophase was observed to be roughly equal to, or even lower than the rate constant in water. 

TABLE 8. Second-order rate constants for reactions of 9-R-fluorenyl carbanions with a-halosulfones and sulfoxides in Me2SO solution at 25 °c63a-87... 

TABLE 7.6 Second-Order Rate Constants for Reaction of Phenolic Monomers with Formaldehyde"... 

These investigators report that the second-order rate constant for reaction B is equal to 1.15 x 10 3 m3/mole-ksec at 20 °C. Determine the volume of plug flow reactor that would be necessary to achieve 40% conversion of the input butadiene assuming isothermal operating conditions and a liquid feed rate of 0.500 m3/ksec. The feed composition is as follows. 

The forward and reverse second-order rate constants for reaction... 

The second-order rate constants for reaction of Co(NH3)jL" (A ) and Co(ND3)jL" (Atd) with and Cr " have been measured. Explain the results shown... 

The second-order decay of the three-coordinate transient (to form a dimer, k = 2 X lO M s ) can be accelerated in the presence of substrates, Ph3P, CO etc. The second-order rate constant for reaction with CO, 1.0 x 10 M s is consistent with an early... 

Bruice and Lapinski (1958) reported that logarithms of second-order rate constants for reaction of p-substituted phenoxide ions with p-nitrophenyl acetate were a linear function of the p/sfa-value of the phenol with a slope of 0-8. Phenolate ions cannot displace... 

Intermediate a-nitrosobenzaldehyde 36 was generated in solution by laser photolysis of 3,5-diphenyl-l,2,4-oxadiazole-4-oxide 37 and its time-resolved infrared (TRIR) spectroscopy has been recorded <2003JA1444>. The second-order rate constants for reaction with diethylamine and 1,3-cyclohexadiene were determined to be (1.3 0.5) x s ... 

However, if it occurs, it appears to be minor. Thus, based on a review of the relevant studies reported in the literature, DeMore et al. (1997) suggest that k l0 = 4.5 X 10-l4e-1260/7 = 6.6 X 10 16 cm3 molecule 1 s 1 at 298 K. This can be compared to an effective second-order rate constant for reaction (9) at 1 atm of 1.3 X 10 12 cm3 molecule-1 s-1. In short, the two-body reaction is more than three orders of magnitude slower than the termolecular process at 1 atm pressure. 

In a series of reports published over the last 10-15 years, Mayr and co-workers obtained second-order rate constants for reactions of carbocations and other electrophiles such as metal-7i complexes with a series of nucleophiles, especially 7t-nucleophiles where a C C bond is formed. An impressive body of reactivity data has been accumulated, and, including data from other groups, correlated by the following equation. 

Figure 4.12. Second-order rate constants for reactions of hydrogen atom donors with various radical types at ambient temperature. Data sources group 14 (IV A) hydrides (15) aminyl radicals (69) amidyl radicals (70) alkyl radials with group 16 (VI A) hydrides (71) acyl radical with PhSeH (72).

Figure 4.13. Second-order rate constants for reactions of tributylstannyl and triethylsilyl radicals with various alkyl halides at ambient temperature. [Data from (74) and (80).]...

Table 4 Second-order Rate Constants for Reactions of [HMoOJ at 25 °C...

Figure 16.3 Second-order rate constants for reaction with HO" in aqueous solution (Ap H0. Eq. 16-7) for a series of organic compounds. Data from http //allen.rad.nd.edu, and Haag and Yao (1992).

The units of k2 are M 1 s 1. If [B] is present at unit activity, the rate is /c2[A], a quantity with units of s We can see that the bimolecular, or second-order, rate constant for reaction of A with B may be compared with first-order constants when the second reactant B is present at unit activity. In many real situations, reactant B is present in large excess and in a virtually constant concentration. The reaction is pseudo-first order and the experimentally observed rate constant /c2[B] is an apparent first-order rate constant. The bimolecular rate constant k2 can be obtained by dividing the apparent constant by [B]. 

Second-order rate constants for reactions of hydroxide ion and butane-2,3-dione monoximate ion with various phosphate, phosphinate, and thiophosphinate esters pass through minima with decreasing water content of water-MeCN and water-/-BuOH mixtures. The initial inhibition is offset by stabilization of die charge-delocalized TSs.234... 

Second-order rate constant for reaction between the ith and jth... 

Calculate (a) the first order rate constant for the reaction of the complex with the solvent, water, (b) the pseudo-first order rate constant for reaction with pyridine and (c) the second order rate constant for reaction with pyridine. 

Based on our calculations, performed on literature data, most likely candidates among DOM components for reaction with N02 are the phenolic moieties. However, given the usual DOM loading in surface waters and the expected second-order rate constants for reaction with N02, we have shown that hydrolysis would usually be the most important sink of nitrogen dioxide in aqueous solution [104, 111-113]. 

Hydroxyl radical reacts rapidly with a wide array of species. Typically, reactions follow second-order kinetics. In many cases, aqueous reactions with hydroxyl radical are diffusion-limited. Two comprehensive sources of second-order rate constants for reactions with hydroxyl radical are available... 

THF can also have an accelerating effect on reactivity, in cases where the weakly basic solvent can get directly involved in the reaction via a catalytic pathway and complexation with the free silene is weak. Such an effect has been observed for the reaction of alcohols with the aryldisilane-derived l,3,5-(l-sila)hexatriene derivatives 21a-c, as shown by the second-order rate constants for reaction of the three silenes by MeOH and TFE in isooctane, MeCN and THF solution (Table 11 note that the third-order rate constants for reaction of 21a-c with MeOH have been omitted)48. Table 11 also includes data for the reactions with acetone in the same three solvents, as an example of a reaction which has no catalytic component47. The rate constants for all three reactions decrease in the order isooctane > MeCN > THF for 21a, which complexes relatively strongly with the ether solvent, as demonstrated by the distinctive red shift in its UV absorption spectrum in THF (kmax = 460 nm) compared to isooctane and MeCN (kmax = 425 nm)48. Compound 21b exhibits a ca 10 nm shift of its absorption band in THF solution while none is detectable in the case of 21c, indicating that the equilibrium constant for THF complexation within this series of silenes decreases with increasing phenyl substitution at... 

The second-order rate constants for reactions of Co(I)(BDHC) with alkyl halides were determined spectrophotometrically at 400 nm (17). These rate constants are listed in Table VII along with those for Co(I)(corrinoid)(vitamin Bi2s) in methanol at 25°C (35). These data indicate that the SN2 mechanism is operative in the reaction of Co(I)(BDHC) the iodides are more reactive with the cobalt complex than the bromides, and the rate decreases with increasing bulkiness of the alkyl donor. The steric effect is more pronounced for Co(I)(BDHC) than for vitamin B12s, which is confirmed by the rate ratios for... 

Table VII. Second-Order Rate Constants for Reactions of Co(I)(BDHC)a and Vitamin B12s6 with Alkyl Halides0...

The results obtained by Ayediran et al. (Table 19) show that the second-order rate constants for reaction of both substrates are... 

Tab. 6.6 Representative examples of second order rate constants for reactions of OH...

Among examples studied are the nitrosation of hydroxylamine and its methyl derivatives (M. N. Hughes et al., 1968), hydrazine (Perrott et al., 1976) and the methylhydrazines (Perrott et al., 1977). In all cases reaction occurred via the conjugate acid of the substrate, and although thiocyanate ion catalysis is more pronounced than that of bromide ion, the second order rate constants for reaction (25) were found to be approximately 100 times less than for nitrosyl bromide. More recent work with both morpholine and aniline showed the... 

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