NMR spectroscopy, dynamic

Limbach H H 1991 Dynamic NMR spectroscopy in the presence of kinetic hydrogen/deuterium isotope effects NMR Basic Principles and Progress vol 23, ed P Diehl, E Fluck, H Gunther, R Kosfeld and J Seelig (Berlin ... 

J. Sandstrom, Dynamic NMR Spectroscopy, Academic Press, New York, 1982. 

G. Binsch, Top. Stereochem. 3 97 (1968) F. G. Riddell, Nucl. Magn. Reson. 12 246 (1983) J. Sandstrom, Dynamic NMR Spectroscopy Academic Press, New %rk, 1982 J. L. Marshall, Nuclear Magnetic Resonance, Veilag Chemie, Deerfield Beach, Florida, 1983 M. Oki, Applications of Dynamic NMR to Organic Chemistry, VCH Publishers, Deerfield Beach, Florida, 1985 Y. Takeuchi and A. P. Marchand, eds.. Applications of NMR Spectroscopy in Stereochemistry and Corformationol Analysis, VCH Publishers, Deerfield Beach, Florida, 1986. 

M. Old, Applications of Dynamic NMR Spectroscopy to Organic Chemistry, VCH Publishers, Deerfield Beach, Florida, 1983. 

Accounting for this effect, it was possible to apply dynamic NMR spectroscopy to measure energy barriers to the prototropic rearrangements of pyrazoles. Temperature-variable spectra of a series of 4-substituted pyra-zoles 5 and 6 have been studied in methanol-d4 solutions and the free energy barriers of the degenerate type 2a 2b tautomerization reported (93CJC1443). 

Preliminary experiments demonstrated that only one slow dynamic process can be generally detected in BENA by dynamic NMR spectroscopy. 

To study this problem in detail, the structures and stereodynamics of BENA were investigated by several physicochemical methods (X-ray diffraction, quantum chemical calculations and dynamic NMR spectroscopy) (467). 

Table 3.28 presents the results of investigation of the stereodynamics in BENA and related compounds by dynamic NMR spectroscopy (467). 

Sandstrom, J. Dynamic NMR Spectroscopy , Academic Press London, 1982. 

The structure of amino-substituted allenylidene complexes merits special attention since those compounds derived from unsymmetrically substimted amines usually give rise to isomeric mixmres in solution (C-N bond rotamers) [19-24, 27, 43]. For complexes tra s-[RuCl =C=C=C(NR R )Me (dppm)2] the rotational energy barriers around the C-N bond could be experimentally determined by dynamic NMR spectroscopy, the high values observed (ca. 85 kJ moP )... 

Casey was able to prepare related zirconocene alkenyl complexes according to Scheme 8.18. Alkene coordination was established by a number of NMR techniques. While zwitterionic compounds 38 allowed the determination of the alkene dissociation energy, AG = 10.5 kcal mol , very similar to that of 35. Thermally more stable complexes were obtained by protonation of 37 with [HNMePh2][B(C5F5)4[. Dynamic NMR spectroscopy and line shape analysis allowed the measurement of the barriers of alkene dissociation (AG = 10.7 and 11.1 kcal mol ), as well as for the site epimerisation ( chain skipping ) at the zirconium center (AG = 14.4 kcal mol" ) (Scheme 8.19) [77]. 

The pyramidal inversion of phosphorus was studied by dynamic NMR spectroscopy using the H signals of N—Me diastereotopic groups in (60) and P signals in Z- and -diastereomers of (61). Kinetics at coalescence temperature revealed the value of AG to increase in the order of increasing electronegativity Si < Sn < Ge <82JOM(224)247>. 

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