Solvent effects in NMR

Dracinsk, M. Bouf, P. Computational analysis of solvent effects in NMR spectroscopy, J. Chem. Theor. Comput. 2009, 6, 288-299. 

Wilson, R. G., J. H. Bowie, and D. H. Williams Solvent Effects in NMR Spectroscopy. Solvent Shifts of Methoxyl Resonances in Flavones Induced by Benzene an Aid in Structure Elucidation. Tetrahedron 24, 1407 (1968). 

An interesting approach to the solvent polarity problem is a statistical evaluation, mainly founded on a factor analysis, of the different scales (C 24). Two main factors, F r which represent 85% of the whole variance for the various scales, seem to be appropriate for representing solvent effects in NMR. In Table 5.1, A6, A, E, Z,... 

Discussion of solvent effects in NMR spectroscopy is discussed more explicitly in Chapter 6, and the authors thank one of our graduate students, Ms. Natalia DeKalb, for acquiring the data in Figures 6.19 and 6.20. A new section on determining the relative and absolute stereochemical configuration with NMR has also been added to this chapter. 

Solvent Effects and NMR Coupling Constants Table 13. Solvent and temperature dependence ofJJp H in phosphine... 

Ronayne, J., Williams, D. H. Solvent Effects in Proton Magnetic Resonance Spectroscopy. Annual Review of NMR Spectroscopy, Vol. 2,pp. 83-124, New York 1969. Laszlo, P. Solvent Effects and Nuclear Magnetic Resonance. Progr. N.M.R. Spectroscopy 3, 231-403(1968). 

We next give Tables 6, 7 and 8 to show representative values for various chemical shifts, couplings and solvent effects in and 13C NMR spectra of pyridine and its iV-oxide and protonated derivatives, in addition to those in the general section (Chapter 2.01), to show the general character of the results obtained and their susceptibility to variation of structure and media. 

Computational methods to study solvent effects on NMR (Sadlej Pecul) and EPR (Barone, Cimino Pavone) parameters are presented and discussed within the PCM as well their generalizations to hybrid continuum/discrete approaches in which the presence of specific interactions (e.g. solute-solvents H-bonds) is explicitly taken into account by including some solvent molecules strongly interacting with the solute. 

J. D. Cargioli, E. A. Williams and R. W. LaRochelle, Solvent Effects in 2<2Si NMR in IXth Organosilicon Award Symposium, Case Western Reserve University, Cleveland, Ohio, 1975, Abstracts, p. 19. 

In the last years, these semiclassical analyses have been substituted by (or supported with) explicit descriptions of the electronic aspects of the solvent effects on NMR properties and in particular on the nuclear shielding. This change of perspective has been made possible by the large development of QM solvation models which have been coupled to QM methodologies initially formulated for isolated systems. 

Because of the ease with which molecular mechanics calculations may be obtained, there was early recognition that inclusion of solvation effects, particularly for biological molecules associated with water, was essential to describe experimentally observed structures and phenomena [32]. The solvent, usually an aqueous phase, has a fundamental influence on the structure, thermodynamics, and dynamics of proteins at both a global and local level [3/]. Inclusion of solvent effects in a simulation of bovine pancreatic trypsin inhibitor produced a time-averaged structure much more like that observed in high-resolution X-ray studies with smaller atomic amplitudes of vibration and a fewer number of incorrect hydrogen bonds [33], High-resolution proton NMR studies of protein hydration in aqueous... 

In general, two different solvent effects on NMR spectra can be distinguished (a) shifts due to a difference in the bulk volume magnetic susceptibility x of the solute and the solvent (b) shifts arising from intermolecular interactions between solute and solvent molecules. Since the bulk susceptibility effect depends on the shape of the sample and, therefore, is not of chemical interest, some form of correction for it is applied. For two... 

The intermolecular solute/solvent interactions may arise from nonspecific interaction forces such as dispersion, dipole-dipole, dipole-induced dipole, etc., as well as from specific interactions found in protic and aromatic solvents. Solvent effects on NMR spectra were first observed by Bothner-By and Glick [226] and independently by Reeves and Schneider [227] in 1957. Since then, the influence of solvent on chemical shifts (and coupling constants) has been extensively studied by scores of workers and has been thoroughly reviewed by several specialists [1-4, 288-237]. 

Somewhat related to the ASIS s are the lanthanide-induced NMR chemical shifts. These involve addition of a lanthanide salt to form a complex, rather than a solvent effect. In fact, aromatic solvents are of the same class as the diamagnetic lanthanide shift reagents cf. reference [415]. 

Argyropoulos, D. S., Archipov, Y., Bolker, H. L, and Heitner, C., P NMR spectroscopy in wood chemistry. Part IV. Lignin models Spin lattice relaxation times and solvent effects in P NMR, Holrforschung 47, 50-56 (1993). 

These results are strongly in favor of those theories of solvent effects on nmr and ir spectra in which only pairwise interactions are considered. 

Significant solvent effects, in particular the effect of solvent dielectric constant, are known to occur for F NMR chemical shifts and this has led to significant differences between literature values for a given species and also has been the subject of considerable theoretical effort. 

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