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Concentration interconversions

Figures 11-7 and 11-8 show plots of velocity versus substrate concentration of the interconversion of D-glyceraldehyde 3-Phosphate, and the conversion of urea, respectively. Figures 11-7 and 11-8 show plots of velocity versus substrate concentration of the interconversion of D-glyceraldehyde 3-Phosphate, and the conversion of urea, respectively.
Because six-membered rings aie nonnally less strained than five-membered ones, pyranose forms are usually present in greater anounts than furanose forms at equilibrium, and the concentration of the open-chain form is quite small. The distribution of carbohydrates among then- various herniacetal forms has been examined by using H and NMR spectroscopy. In aqueous solution, for exanple, D-ribose is found to contain the various a- and p-furanose and pyranose forms in the amounts shown in Figure 25.5. The concentration of the open-chain form at equilibr ium is too small to measure directly. Nevertheless, it occupies a central position, in that interconversions of a and p anorners and furanose and pyranose forms take place by way of the open-chain form as an intermediate. As will be seen later, certain chemical reactions also proceed by way of the open-chain form. [Pg.1039]

In this chapter, we have examined the use of cells and enzymes to chemically transform lipids. We have had to be selective and have predominantly focused attention on the transformation of sterols and steroids. We first explained why these compounds were commercially important and why they only occur in low concentrations in natural systems. We pointed out that a very large number of reaction types are possible, but those which have found greatest use include stereospedfic hydroxylations, alcohol/ketone interconversion, hydrolysis, conjugation and isomerisation. [Pg.340]

Opposing reactions. The reversible interconversion of d.y-[Cr(cn)2(OH)2 + to trans is characterized by an equilibrium constant of 0.16 and a forward rate constant of 3.30 X 10 4 s"1.In an experiment starting with the pure cis isomer, how long does it take to form half the equilibrium concentration of trans Starting with pure trans, how long does it take for half the equilibrium concentration of trans to form ... [Pg.67]

Owing to the reversible nature of the allylic sulfenate/allylic sulfoxide interconversion, the stereochemical outcome of both processes is treated below in an integrated manner. However, before beginning the discussion of this subject it is important to point out that although the allylic sulfoxide-sulfenate rearrangement is reversible, and although the sulfenate ester is usually in low equilibrium concentration with the isomeric sulfoxide, desulfurization of the sulfenate by thiophilic interception using various nucleophiles, such as thiophenoxide or secondary amines, removes it from equilibrium, and provides a useful route to allylic alcohols (equation 11). [Pg.724]

Fig. 2. Free-enthalpy diagram of the interconversion 87 6 at 20°C in FHSO3—SbFs (concentrations expressed in mole litre i). Underlined numbers directly from experimental data. Fig. 2. Free-enthalpy diagram of the interconversion 87 6 at 20°C in FHSO3—SbFs (concentrations expressed in mole litre i). Underlined numbers directly from experimental data.
Figure 5. Guanine-nucleotide-dependent receptor interconversion from LRG" to LR. Penneabilized cells (10 /mL) (no GTPyS 1 ml Mg " ) were allowed to bind FLPEP for 1 min. Data analysis begins with the addition of antibody to fluorescein (after 60 s, but not indicated). At 90 s (indicated), GTPyS is added to induce interconversion to the rapidly dissociating state. The guanine nucleotide concentrations are shown (saturated at 10" If). The solid lines are the fit to the onestep model shown in the inset, and the k for the fit is shown at the end of each solid line. Data... Figure 5. Guanine-nucleotide-dependent receptor interconversion from LRG" to LR. Penneabilized cells (10 /mL) (no GTPyS 1 ml Mg " ) were allowed to bind FLPEP for 1 min. Data analysis begins with the addition of antibody to fluorescein (after 60 s, but not indicated). At 90 s (indicated), GTPyS is added to induce interconversion to the rapidly dissociating state. The guanine nucleotide concentrations are shown (saturated at 10" If). The solid lines are the fit to the onestep model shown in the inset, and the k for the fit is shown at the end of each solid line. Data...
Two steady state conditions apply one to the total radical concentration and the other to the concentrations of the separate radicals Ml- and M2-. The latter has already appeared in Eq. (2), which states that the rates of the two interconversion processes must be equal (very nearly). It follows from Eq. (2) that the ratio of the radical population, Mi - ]/ [Mpropagation reaction rate constants. The steady-state condition as applied to the total radical concentration requires that the combined rate of termination shall be equal to the combined rate of initiation, i.e., that... [Pg.199]

During the lifetime of a root, considerable depletion of the available mineral nutrients (MN) in the rhizosphere is to be expected. This, in turn, will affect the equilibrium between available and unavailable forms of MN. For example, dissolution of insoluble calcium or iron phosphates may occur, clay-fixed ammonium or potassium may be released, and nonlabile forms of P associated with clay and sesquioxide surfaces may enter soil solution (10). Any or all of these conversions to available forms will act to buffer the soil solution concentrations and reduce the intensity of the depletion curves around the root. However, because they occur relatively slowly (e.g., over hours, days, or weeks), they cannot be accounted for in the buffer capacity term and have to be included as separate source (dCldl) terms in Eq. (8). Such source terms are likely to be highly soil specific and difficult to measure (11). Many rhizosphere modelers have chosen to ignore them altogether, either by dealing with soils in which they are of limited importance or by growing plants for relatively short periods of time, where their contribution is small. Where such terms have been included, it is common to find first-order kinetic equations being used to describe the rate of interconversion (12). [Pg.333]

We have examined the effects of concentration, temperature, solvent and added electrolyte on the kinetics of this structural interconversion. In all instances, the kinetics are well described by the rate law for a reversible first-order reaction [Equation 1] ... [Pg.67]

Step 1. An enzymatic reaction is considered as a cyclic process that displays all the interconversions among the various enzyme forms involved. For each step in the reaction a rate constant is defined in terms of the product of the actual rate constant for that step and the concentration of free substrate involved in the step. Hence, the cyclic form of the reaction scheme given in Equations 17.6, 17.7, and 17.8 is represented by... [Pg.682]

Some recent interest in the technetium chemistry has been focused on complexes possessing a Tc=N3+ core. Tetrachloronitridotechnetate(VI) complexes can easily be synthesized by the reaction of pertechnetate with sodium azide in concentrated hydrochloric acid [34], Although its square-pyramidal structure resembles that of tetrachlorooxotechnetate(V) complexes, stable character of the nitrido complexes in aqueous solution shows a remarkable contrast to the oxo complexes. However, when a strong acid and a coordinating ligand are absent, the interconversion of di(p-oxo)nitridotechnetium(VI) complexes to the monomeric form occurs in the following complicated manner [35]... [Pg.267]

Dipolar cycloaddition of diazomethane to aldehydes can successfully be used for the preparation of tetrahy-drooxadiazole derivatives. Photochemical interconversion of 3-acylamino-l,2,5-oxadiazole derivatives leads to 1,3,4-oxadiazoles, though the method suffers from lack of selectivity. Many reports concentrate only on the synthesis and applications of new 1,3,4-oxadiazoles substituted with a wide variety of groups without introducing much of new chemistry. [Pg.446]

It is not overly difficult to include the effects of interconversion of hydrogen among its charge states if these are equilibrated with the local carrier concentrations and if we continue to neglect complex formation and assume that the spatial scale of the diffusion-migration phenomena is large... [Pg.271]

It was found that the geminal methyl substituents of chlorostannane 29 are nonequivalent in nonpolar solvents such as benzene, toluene or CCI4 at concentrations less than 0.2 M. At higher concentration peak coalescence was observed, indicating rapid interconversion of the enantiomers on the NMR time scale. The addition of DMSO, acetone or HC1 also caused coalescence, even in nonpolar media. It was concluded that inversion at tin in 29 was occurring by self-association in nonpolar solvents or through ligand addition. In each case, a transient five-coordinated Sn species is a likely intermediate. [Pg.207]

The second and third relaxation processes were coupled, where the observed rate constants differed by a factor of 3 to 7 and the rate constant for each relaxation process varied linearly with the DNA concentration.112 This dependence is consistent with the mechanism shown in Scheme 2, where 1 binds to 2 different sites in DNA and an interconversion between the sites is mediated in a bimolecular reaction with a second DNA molecule. For such coupled kinetics, the sum and the product of the two relaxation rate constants are related to the individual rate constants shown in Scheme 2. Such an analysis led to the values for the dissociation rate constants from each binding site, one of the interconversion rate constants and the association rate constant for the site with slowest binding dynamics (Table 2).112 The dissociation rate constant from one of the sites was similar to the values that were determined assuming a 1 1 binding stoichiometry (Table 1). [Pg.189]


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