Kinetically indistinguishable terms

Kilocalories, 14 conversion of, 246 Kilojoules, 14 conversion of, 246 Kinetically equivalent terms, 123 Kinetically indistinguishable terms, 123 Kinetic equivalence, 123, 136, 217, 349 in intramolecular catalysis, 267 salt effect and, 411 Kinetic isctdpe effects, 292 primaiy, 293 secondary, 298 solvent, 300... 

The rate terms A [HA] and A [H ][A ] are said to be kinetically equivalent or kinetically indistinguishable. There is no purely kinetic basis upon which to make a choice between them in Chapter 5 we will see why this is so, but a simple interpretation is that the two terms describe equivalent chemical compositions of atoms and charges. 

The second step is essentially irreversible because of the pA of the product acid thus, the catalyst is consumed. If the substrate is ionizable (say HS), a rate term A [HS][OH ] is kinetically indistinguishable from the term fc [S ]. Thus, the mechanistic involvement of a catalytic hydroxide ion is not proved, in such a case, by the rate equation. 

To summarize the analysis of pH profiles, even complex ones, is not an arcane or difficult art. Systematic analysis in terms of ionic equilibria, predominant species, and the reaction orders with respect to [H+] provides the solution. Kinetically indistinguishable alternatives can never, by definition, be distinguished from the kinetic data contained in the pH profile. Other measurements, including some alluded to earlier and others given in Chapter 10, may, however, allow these distinctions. 

The three independent rate constants /cqK, and kfc = kf + k, Kf fully determine the kinetic properties of Scheme 2, because the rate constants kf for enolization are related to those of the reverse reactions, Equation (9), where Kw is the ionization constant of water. We use primed symbols for the enolization of the neutral ketone K. In the rate equation for enolization, the terms k(f and k e ATW/AT are kinetically indistinguishable (see Equation (10) below). 

The occurrence of general acid-catalyzed hydroxylaminolysis or methoxylaminolysis of thiol esters or amides has been described in Section IIB in terms of kinetically important tetrahedral intermediates. Two kinetically indistinguishable mechanisms for general acid-catalyzed aminolysis reactions are represented by transition states 42 and 43. Mechanism 42 involves a prior protonation of the ester followed by a general base-catalyzed aminolysis mechanism 43 is a general acid-assisted nucleophilic reaction of the amine. Mechanism 42 can be ruled out in the hydrazinolysis of phenyl acetates (Bruice and Benkovic, 1964) and in the hydrazinolysis of S-thiolvalerolactone (Bruice et al., 1963) on the basis of a calculated rate constant which is greater than the diffusion-controlled limit. Mechanism 43 is therefore correct. 

In molecular terms, the movement of an ion across a membrane via a channel can best be described as a series of "hops" along the stationary channel molecule. The ion-transporter interactions that facilitate ion translocation replace ion-water interactions on either side of the membrane. The energy barrier for direct ion diffusion across the membrane is directly due to the instability of the ion in the nonpolar membrane interior. lon-chatmel interactions significantly lower the barrier and thus facilitate diffusion.A similar argument applies to carrier-mediated transport, with the result that chaimels and carriers are kinetically indistinguishable. However, activation barriers for channel-mediated diffusion are expected to be much lower than the activation barrier for carriers. " with the result that the maximum transport rates of channels are typically several orders of magnitude higher than those of carriers. 

For the quantum mechanical ideal gases, we begin with the construction of a properly normalized wavefunction for N indistinguishable free particles of mass m. In this case the hamiltonian of the system consist of only the kinetic energy term,... 

The realization of the occurrence of intermolecular GA catalysis comes from the experimental fact of the presence of a kinetic term kgJBH+][NuH][Sub] (where BH+ is the GA, NuH is the nucleophile, and Sub is the substrate) in the rate law for the nucleophilic reaction between NuH and Sub in the presence of BH+. But this kinetic term is kinetically indistinguishable from kinetic term k[H+][B][NuH][Sub], which represents SA-GB catalysis or SA-nucleophilic catalysis. However, these kinetically indistinguishable catalytic mechanisms can be resolved, at least qualitatively, as described in the following text. 

It could be claimed that such an El solvolytic elimination would be indistinguishable kinetically from a bimolecular (E2) elimination, in which EtOH was acting as base, because the [EtOH] term in the E2 rate law,... 

The importance of the changes in quaternary structure in determining the sigmoidal curve is illustrated nicely by studies of the isolated catalytic trimer, freed by p-hydroxymercuribenzoate treatment. The catalytic subunit shows Michaelis-Menten kinetics with kinetic parameters that are indistinguishable from those deduced for the R state. Thus, the term tense is apt in the T state, the regulatory dimers hold the two catalytic trimers sufficiently close to one another that key loops on their surfaces collide and interfere with conformational adjustments necessary for high-affinity substrate binding and catalysis. 

Through this step and based on experimental evidence we try to develop the appropriate model to describe the test chamber kinetics. As was anticipated in the introduction of this Chapter, from a conceptual point of view, two broad categories of models can be developed empirical-statistical and physical-based mass transfer models. It should be emphasized that, in several cases, even the fundamentally based mass transfer models are indistinguishable from the empirical ones. This happens because the mass transfer models are generally very complex in both the physical concept involved and the mathematical treatment required. This often leads the modelers to introduce approximations, making the mass transfer models not completely distinguishable from some empirical models in terms of both functional formulations and descriptive capabilities. Considering the current status of models which have been developed to describe VOC emissions (and/or sink processes), we could define the mass transfer models as hybrid-empirical models. 

Quantitative immunoprecipitation experiments were performed to determine the relationship between enzyme activity and immuno-precipitable material for purified rat liver, N1S167 (sensitive parent) and 5-2 (resistant cell) ADA s. Figure 1 shows that the same amount of antibody precipitated the same amount of enzymatic activity for all three proteins. Thus, ADA s from rat liver and dCF sensitive hepatoma and resistant hepatoma cells are indistinguishable in terms of kinetic, physical and immunological properties. The increase in ADA activity in dCF cells is clearly due to an increase in the number of molecules of a structurally normal enz3nme. 

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