Variable Temperature Nuclear Magnetic Resonance Studies of Some Five-Membered Ring Chelate Complexes

1975 ◽  
Vol 53 (7) ◽  
pp. 1038-1045 ◽  
Author(s):  
William R. Cullen ◽  
Laurance D. Hall ◽  
John E. H. Ward
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Temperature Dependence ◽  
Significant Variation ◽  
Conformational Equilibrium ◽  
Variable Temperature ◽  
Membered Ring ◽  
Coupling Constants ◽  
Chelate Complexes ◽  
Magnetic Resonance Studies

The temperature dependence of the n.m.r. spectra of nine ditertiary arsine chelate complexes of formula (CH3)2AsC(3)(3′)C(4) (4′)As(CH3)2M(CO)3X has been studied (M = Mo, Cr; X = CO; M = Mn; X = halogen; (3), (3′), (4), (4′) = H, F, Si(CH3)3, CN; but not all combinations ). Significant variation in coupling constants, indicating a shift in the conformer populations, was found only for the CHFCF2 bridged Mn(CO)3Cl complex, the CH2CF2 bridged Mn(CO)3Cl complex, and the CHFCHF bridged Mo(CO)4 complex. In the last case the 3JHH coupling constants were used to estimate ΔH ∼ 1 kcal/mol and ΔS ∼ 3 e.u for the conformational equilibrium.

Studies of specifically fluorinated carbohydrates. Part I. Nuclear magnetic resonance studies of hexopyranosyl fluoride derivatives

1969 ◽  
Vol 47 (1) ◽  
pp. 1-17 ◽  
Author(s):  
L. D. Hall ◽  
J. F. Manville ◽  
N. S. Bhacca
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Angular Dependence ◽  
Chemical Shifts ◽  
Relative Orientation ◽  
Coupling Constants ◽  
Pyranose Ring ◽  
Spectral Parameters ◽  
Magnetic Resonance Studies ◽  
Nuclear Magnetic

A detailed study has been made of both the 1H and 19F nuclear magnetic resonance (n.m.r.) spectra of a series of hexopyranosyl fluoride derivatives. Some of the 1H spectra were measured at 220 MHz. The 1H spectral parameters define both the configuration and the conformation of each of these derivatives. Study of the 19F n.m.r. parameters revealed several stereospecific dependencies. The 19F chemical shifts depend upon, (a) the orientation of the fluorine substituent with respect to the pyranose ring and, (b) the relative orientation of other substituents attached to the ring; for acetoxy substituents, these configurational dependencies appear to be additive. The vicinal19F–1H coupling constants exhibit a marked angular dependence for which Jtrans = ca. 24 Hz whilst Jgauche = 1.0 to 1.5 Hz for [Formula: see text] and 7.5 to 12.6 Hz for [Formula: see text] The geminal19F–1H couplings depend on the orientation of the substituent at C-2; when this substituent is equatorial JF,H is ca. 53.5 Hz and when it is axial the value is ca. 49 Hz.

Studies of specifically fluorinated carbohydrates. Part II. Nuclear magnetic resonance studies of pentopyranosyl fluoride derivatives

1969 ◽  
Vol 47 (1) ◽  
pp. 19-30 ◽  
Author(s):  
L. D. Hall ◽  
J. F. Manville
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Magnetic Resonance Studies ◽  
Conformational Model ◽  
Nuclear Magnetic

Detailed studies, by 1H and 19F nuclear magnetic resonance spectroscopy, of a series of fully esterified pentopyranosyl fluorides, show that all such derivatives favor that conformer in which the fluorine substituent is axially oriented. This conclusion is supported by separate considerations of the vicinal and geminal19F–1H and 1H–1H coupling constants, of the long-range (4J) 1H–1H and 19F–1H coupling constants and of the 19F chemical shifts. The limitations of the above conformational model are discussed.

Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a 2Hmr study of H/D exchange in tricyclic ketones

1984 ◽  
Vol 62 (7) ◽  
pp. 1385-1391 ◽  
Author(s):  
A. K. Cheng ◽  
Ashim K. Ghosh ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Membered Ring ◽  
Deuterium Incorporation ◽  
Magnetic Resonance Studies ◽  
Endo Isomer ◽  
Exchange Processes ◽  
Initial Transformation ◽  
Nuclear Magnetic

The effect of strongly basic conditions (t-BuO−/t-BuOH/185 °C) on the exo and endo isomers of 7,7-dimethyltri-cyclo[3.2.1.02.4]octan-6-one has been examined. While the exo isomer is stable, the endo isomer readily rearranges to 4,4-dimethyltricyclo[3.3.0.02.8]octan-3-one (6) which subsequently undergoes reduction of the three-membered ring. The initial transformation is one of very few examples of γ-enolate rearrangement. Experiments in tert-buiyl alcohol-O-d1 were carried out to establish the several sites of deuterium incorporation in the initial ketones and in 6 using 2Hmr. These results reveal the stereochemistry of γ-enolate formation and cleavage as well as the stereoselectivities and relative rates of the exchange processes.

Nuclear magnetic resonance studies. X. Determination of the thermodynamic parameters of the self-association of tricyclic aromatic aldehydes in solution

1967 ◽  
Vol 45 (3) ◽  
pp. 213-219 ◽  
Author(s):  
Gurudata ◽  
R. E. Klinck ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Temperature Dependence ◽  
Thermodynamic Parameters ◽  
Aromatic Aldehydes ◽  
The Self ◽  
Kcal Mole ◽  
Magnetic Resonance Studies ◽  
Self Association

The temperature dependence of the formyl proton shieldings of 9-anthraldehyde and 9-phenanthraldehyde in chloroform solutions has been measured. Four concentrations in the range 0.5–5.0 mole % were examined over the temperature interval − 60 to + 90 °C. From these results, the enthalpies and entropies of formation have been estimated for the complex formed by the self-association of two aldehyde molecules. The calculations indicate the ΔH and ΔS values to be − 1.9 ± 0.3 kcal/mole and − 6 ± 1 e.u., respectively. These results are compared with other available data.

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