Kinetic isotope method

Calculations according to the kinetic isotope method for the mixture of inactive -hexane and -hexene showed that 92-97% of the total... 

M. B. Neiman and D. Gal, The Kinetic Isotope Method and Its Application, Akademic Kiado, Budapest, 1971. 

The enzyme mechanism of NA of influenza virus has been investigated by kinetic isotope methods, NMR, and a molecular dynamics simulation of the enzyme-substrate complex. 

The kinetic-isotope method is distinctly different from the tracer method. Here we make use of the fact that isotopic substitution leads to changes in rate constants which in some cases can be satisfactorily correlated with the reaction mechanism. 

The kinetic isotope method was also applied to study whether the stepwise or direct route is valid for the dehydrogenation of the cyclohexane ring.[bi4,67] mentioned before, plotting specific radioactivities as a function of the contact time confirmed the predominance of direct pathway on Re and the stepwise dehydrogenation on chromia. 

Neiman MB, Gal D, The Kinetic Isotope Method and Its Applications, Akademiai Kiado, Budapest — Elsevier, Amsterdam, 1971. 

The mechanism of the low-temperature oxidation of methane has also been studied following the kinetic isotopic method By adding known portions of H[ " C)HO and CO to the methane-air mixture and measuring the changes with time of the specific activities of formaldehyde and carbon monoxide in the mixture, it has been established that formaldehyde is the unique precursor of carbon monoxide and the oxidation of methane proceeds according to equation 227. A suggestion has been made that... 

Applications of the kinetic isotopic method to the study of gas-phase oxidations of alkanes as well as liquid-phase oxidation of cyclohexane (equation 229) are presented in a monograph by Neiman and Gal . ... 

Kezdy-Swinboume method, 26-27 Kinetic element effect, 110-111 Kinetic isotope effects (kie), 214-219 inverse, 217... 

Anderson and Bonner made the first detailed kinetic study on the exchange using the isotopic method ( Cr) and a separation method based on the conversion of Cr(II) into Cr(IIl) oxalate and an ion-exchange treatment. To prevent oxidation of Cr(II) during exchange a hydrogen atmosphere was maintained over the reaction mixture. The rate law found to be obeyed for the concentration ratio range Cr(III)/Cr(II) of between 3.3 x 10 and 2.0 in perchlorate media was... 

Altman and King made the first detailed study of this system, using Cr(ril) solutions containing only the monomeric species and Cr(VI) solutions which had been allowed to age. The isotopic method and lead chromate precipitation separation were used to obtain kinetic data at a temperature of 94.8 °C. Over the range of concentrations, Cr(VI) 2.3x10 to 8.4x10 A/, Cr(III) 1.8x10 to... 

Horne has studied the kinetics of exchange in aqueous perchlorate media at temperatures down to —78 °C by the isotopic method ( Fe) and dipyridyl separation. The same rate law in these ice media as in aqueous solution was observed, although the acid dependence was small. Horne concluded that the same exchange mechanism occurs in solid and liquid solvent. Evidence for a Grotthus-type mechanism has been summarised. ... 

Baker et al, have obtained some kinetic data on the exchange reactions between the 1,10-phenanthroline, 2,2 -dipyridine and 2,2, 2"-tripyridine complexes of Co(III) and Co(ll) in both H2O and D2O solution. The isotopic method ( Co) and separations involving either extraction of Co(II) with organic solvents (n-hexanol-ether or saturated sodium acetate in n-hexanol) or precipitation of Co(III) as Co(phen)3(l3)3 were used. For the 1,10-phenanthroline system, a rate law... 

Westaway KC, T Koerner, Y-R Fang, J Rudzinski, P Paneth (1998) A new method of determining chlorine kinetic isotope effects. A a/ Chem 70 3548-3552. 

Today a good understanding of transition state structure can be obtained through a combination of experimental measurements of kinetic isotope effects (KIE) and computational chemistry methods (Schramm, 1998). The basis for the KIE approach is that incorporation of a heavy isotope, at a specific atom in a substrate molecule, will affect the enzymatic reaction rate to an extent that is correlated with the change in bond vibrational environment for that atom, in going from the ground state to the... 

Major DT, Gao J (2007) An integrated path integral and free-energy perturbation-umbrella sampling method for computing kinetic isotope effects of chemical reactions in solution and in enzymes. J Chem Theory Comput 3 949—960... 

The density functional theory calculations of primary 14C KIE and secondary deuterium kinetic isotope effects (SKIE)220 did not reproduce satisfactorily all the experimentally determined 14C KIE and deuterium (4,4-2H2)- and 6,6-2H2-SKIE, though the non-local DFT methods provide transition state energies on a par with correlated molecular orbital theory221. 

This method gave a primary hydrogen-deuterium kinetic isotope effect of 1.3 for the reaction between the aryl radical and tributyltin hydride. This isotope effect is smaller than the isotope effect of 1.9 which San Filippo and coworkers reported for the reaction between the less reactive alkyl radicals and tributyltin hydride163 (vide infra). The smaller isotope effect of 1.3 in the aryl radical reaction is reasonable, because an earlier transition state with less hydrogen transfer, and therefore a smaller isotope effect164, should be observed for the reaction with the more reactive aryl radicals. 

Table 3 collects the results obtained by different authors on the reaction of 0s04(NH3) with ethylene. Though the methods were not identical, the results are very similar, and in all cases there is a clear preference of the [3+2] over the [2+2] pathway. Additional confirmation was provided by a combined experimental and theoretical study using kinetic isotope effects (KIEs) to compare experiment and theory. Kinetic isotope effects were measured by a new NMR technique [25] and compared to values, which are available from calculated transition states. It showed that indeed only the [3+2] pathway is feasible [10]. 

This topic has been reviewed in The Chemistry of the Functional Groups series published in 19821. It is not the purpose of this chapter to provide a complete literature review. Rather, this chapter will discuss some of the new methods of measuring and interpreting kinetic isotope effects that have been used to determine the mechanisms of the reactions of amines and amine derivatives. 

Abstract The statistical thermodynamic theory of isotope effects on chemical equilibrium constants is developed in detail. The extension of the method to treat kinetic isotope effects using the transition state model is briefly described. 

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