Nuclear magnetic resonance rate constant

First order rate constant k, for the rotation about the C-N bond in N, N-dimediylnicotinamide (3) measured at different temperatures by nuclear magnetic resonance (NMR) are ... 

In the previous section was given the experimental demonstration of two sites. Here the steady state scheme and equations necessary to calculate the single channel currents are given. The elemental rate constants are thereby defined and related to experimentally determinable rate constants. Eyring rate theory is then used to introduce the voltage dependence to these rate constants. Having identified the experimentally required quantities, these are then derived from nuclear magnetic resonance and dielectric relaxation studies on channel incorporated into lipid bilayers. 

More advanced scale was proposed by Kamlet and Taft [52], This phenomenological approach is very universal as may be successfully applied to the positions and intensities of maximal absorption in IR, NMR (nuclear magnetic resonance), ESR (electron spin resonance), and UV-VS absorption and fluorescence spectra, and to many other physical or chemical parameters (reaction rates, equilibrium constant, etc.). The scale is quite simple and may be presented as ... 

This technique has been taken to new heights through the use of 2-D nuclear magnetic resonance " to assign many, if not all, exchangeable protons in terms of the residues to which they are attached. As a result, one can assess individual rate constants defining the kinetics of exchange. 

Anomeric interconversion of sugars and their derivatives is typically relatively slow, but anomerization of phos-phorylated sugars is usually faster. Values for the rate constants can be obtained by nuclear magnetic resonance techniques. For example, the conversion of /3-fructose... 

Hodson, J., The Estimation of the Photodegradation of Organic Compounds by Hydroxyl Radical Reaction Rate Constants Obtained from Nuclear Magnetic Resonance Spectroscopy Chemical Shift Data, Chemosphere, 17, 2339-2348 (1988). 

A second steady-state method involves the analysis of the broadening of the nuclear magnetic resonance spectra of phospholipids in bilayers containing low concentrations of spin-labeled phospholipids. A theoretical analysis of the relation between this line broadening and diffusion rates has been given by Brulet and McConnell.3 [In this paper (6) is not correct the subsequent equations are nonetheless correct. For an alternative derivation, see Brulet.2] In this paper it is shown that a number of measurements of nuclear relaxation rates T71 of nuclei in phospholipids are consistent with lateral diffusion constants in the range 10 7 to 10 R cm2/s. 

Nuclear magnetic resonance (nmr) 10 4 to 10 2 Changes in nuclear spin orientations in a magnetic field Chemical shifts and coupling constants rapid reaction rates (Sections 9-10, 27-1, and 27-2)... 

Physical phenomena other than rates and equilibrium constants can be correlated by Hammett-type relationships. For example, as Figure 2.4 shows, in 13C nuclear magnetic resonance spectroscopy (called Cmr) the chemical shift of the cationic carbon in 17 is correlated by Brown s cr + values.21 And the C=0... 

Having introduced the correlation of Fig. 1, we may return to the stabilities of alkyl cations. Rate constants for the hydration of secondary and primary alkenes have been measured in concentrated solutions of aqueous sulfuric acid by Lucchini and Modena97 and by Tidwell and Kresge42 using proton nuclear magnetic resonance (NMR) or UV to monitor progress of the reactions. It is conceivable that the reactions involve a concerted addition of a proton and water molecule to the alkenyl double bonds. However, the very weak basicity of water under the conditions of reaction makes this unlikely, and the steep acidity dependences of the reactions (e.g., m =-1.65) is... 

Jensen et al43 have confirmed both the stoichiometry of equation (17), and the fourth-order rate expression (18) for the symmetrisation of the tert.-butyl ester of a-carboxybenzylmercuric bromide in a study by nuclear magnetic resonance. The fourth-order rate coefficient remained constant at about 15 x 10-4 l3.mole-3. sec-1 at 31.4 °C over a wide range of initial concentrations of both the mercuric compound and of ammonia. Of mechanisms B and C, these workers preferred C. 

Hodson, J. 1988. The estimation of the photodegradation of organic compounds by hydroxyl radical reaction rate constants obtained from nuclear magnetic resonance spectroscopy chemical shift data. Chemosphere 17 2339-2348. 

An examination of the structure of lanthanide(III) ion complexes in solution using nuclear magnetic resonance is made in considerable detail. The importance of hydration in both the inner and outer spheres is stressed. The structural data are then used in an attempt to understand the stability constants and the rates of exchange of bound ligands. Fluctional properties are also analysed. Finally, the importance of the structures, the stability constants and the kinetic properties are related to the effects of Ln(III) ions, and through them Ca(II) ions, in biological systems. 

In this experiment, nuclear magnetic resonance (NMR) techniques will be used to determine the specific rate constants and for the forward and reverse reactions as well as the value for the equilibrium constant K. Like the hydrolysis of many other organic compounds, this reaction can be acid catalyzed and the effect of hydrogen-ion concentration on the kinetics can be studied. Furthermore, the dependence of y, , and K on temperature will be measured and used to evaluate activation energies. 

The rate constant (36) and (37) as a function of temperature correlated well with the experimental data obtained for the carboxylic acid protons of crystalline perprotobenzoic acid and ring-deuterobenzoic acids by nuclear magnetic resonance 7) [75] and inelastic neutron scattering (for an analysis of the experiment see Refs. 76 and 77). It should be noted that some of the major parameters of the model (for instance,. /) allowed the direct determination by fluorescence line narrowing technique. 

The addition of a chemical species with a large dielectric constant to induce desired microwave effects in matrices devoid of such substances, or lacking substances with significantly different dielectric constants, can be compared, on a conceptual basis, to cross-polarisation experiments carried out in nuclear magnetic resonance spectroscopy (see Chapter 6). In that case, a nucleus that relaxes relatively rapidly is excited selectively and allowed to transfer that excitation energy to neighbouring nuclei with low or relatively lower relaxation rate (e.g., nuclei being cross-polarised to nuclei). 

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