scholarly journals Further Nuclear Magnetic Resonance Studies of Flavone

1994 ◽  
Vol 12 (2) ◽  
pp. 85-89 ◽  
Author(s):  
Cirilo García-Martínez ◽  
Martha S. Morales-Rios ◽  
Pedro Joseph-Nathan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Carbonyl Group ◽  
Isotope Shift ◽  
Coupling Constants ◽  
Magnetic Resonance Studies ◽  
Isotope Shifts ◽  
Nuclear Magnetic

The incorporation of 92.7% of13C at the carbonyl group of flavone allowed to measure two- and three-bond carbon-carbon coupling constants which range from 1.4 to 3.5 Hz, and to measure two-, three- and four-bond carbon-hydrogen coupling constants which range from 0.3 to 3.8 Hz. A mixture of unlabelled flavone1with its 4-13C labelled analogue2further allowed to measure one-bond induced isotope shifts of -15.5 and -16.2 ppb for C-3 and C-4a, respectively, and a three bond induced isotope shift of +3.7 ppb for C-I'.

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 on Fluorides of Trivalent Phosphorus

1965 ◽  
Vol 20 (2) ◽  
pp. 104-109 ◽  
Author(s):  
G. S. Reddy ◽  
R. Schmutzler
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Trivalent Phosphorus ◽  
Magnetic Resonance Studies ◽  
Regular Change ◽  
Nuclear Magnetic Resonance Spectra ◽  
Multiple Substitution ◽  
Nuclear Magnetic

The P31, F19, and H1 nuclear magnetic resonance spectra of a new series of compounds of the types (RO)nPF3-n and (R2N)nPF3-n (n = 1,2) have been studied. A regular change in the chemical shifts and coupling constants has been observed with multiple substitution. The changes in the coupling constants have been explained on the basis of the electronegativity of the atoms attached to phosphorus. Some long-range coupling constants between hydrogen and fluorine separated by five bonds were observed.

Nuclear Magnetic Resonance Studies. XXIII. Long-range 1H–1H Couplings (JHCCOCH) in some Methyl Bicyclo[2.2.1]heptane-2-carboxylates

1971 ◽  
Vol 49 (12) ◽  
pp. 2152-2155 ◽  
Author(s):  
H. Brouwer ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Coupling Constants ◽  
Magnetic Resonance Studies ◽  
Nuclear Magnetic

The methoxyl proton signals of several 3-substituted 2-carbomethoxybicyclo[2.2.1]hept-5-enes and -heptanes appear as doublets because of 1H–1H coupling over five σ-bonds (5J). The dependence of these long-range coupling constants on the nature and orientation of 2- and 3- substituents is discussed in terms of the probable conformations of the 2-carbomethoxyl groups.

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