Isotope exchange rate profiles

In isotope exchange studies, if we are plotting v x versus a substrate-product pair, we can encounter a number of types of exchange rate profiles, including h5 erbolic (H), or sigmoidal (S) plots with no, partial or complete depression of... 

Most isotopic exchange studies are done between A and Q, or B and P, and not with A and P they usually afford exchange-rate profiles that are hyperbolic or... 

Aromatic enols, that is, phenols, are generally more stable than their ketone tautomers. The pH-rate profile for the enolization reaction of 2,4-cyclohexadienone to parent phenol is shown in Fig. V.44 The rate constant kK of the reverse reaction was determined at pH = 1 by measuring the rate of isotopic exchange and correcting for isotope effects to determine the enolization constant Kb = = 5.4 x 1012, pA E = -12.73. The dashed line in... 

Figure 20. Schematic oxygen isotope concentrations in both solid and water (gas), for solid-flnid exchange experiment. The diagram shows the effect of fast (large K/D) and slow (small K/D) snrface exchange on the isotope profile in the solid. K is the snrface exchange rate constant and D is the diffusion coefficient.

Transport properties (separate determination of electronic and ionic conductivity, oxygen tracer diffusion and chemical diffusion) and surface stages (rate/constant of exchange) parameters of dense ceramics can be studied by several methods, such as electronic blocking polarization methods [32-34], O tracer profile analysis by SIMS [26, 27, 29, 35], study of the isotope exchange kinetics by gas-phase analysis of the isotope composition [27,... 

In deeper waters the deficiency of from its uranium precursor is dramatic (Table 5.5) because this thorium isotope has a very long half hfe (c. 75 000 y) and thus particle scavenging is much more effective at removal than the ingrorvth toward secular equilibrium with Bacon and Anderson (1982) showed that depth profiles of dissolved and particulate °Th could be used to demonstrate the dynamic relationship of metal exchange between particulate and dissolve forms. They argued that the thorium-uranium isotope pair could be used as a tracer of particle removal rates for those metals that faU in the category of adsorbed in Fig. 1.3. 

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