Proton Magnetic Resonance Studies of Long-range Coupling Constants: Conformational Dependence of the 4J Coupling Between Side Chain and Ring Protons in Formylheterocycles

1973 ◽  
Vol 51 (4) ◽  
pp. 573-581 ◽  
Author(s):  
Bernard Pierre Roques ◽  
Suzanne Combrisson
Keyword(s):  
Proton Magnetic Resonance ◽  
Aromatic Aldehydes ◽  
Coupling Constants ◽  
Side Chain ◽  
Coupling Constant ◽  
Precise Analysis ◽  
J Coupling ◽  
Electron Contribution ◽  
Replacement Technique ◽  
J Coupling Constants

The 4J coupling constant between side chain and ring protons is studied on particular models of planar heterocyclic aldehydes.The preferential conformation of these molecules is established by use of the "zig–zag" rule for the 5J coupling constant. This allows precise analysis of the 4J coupling across cc and ct pathways.The sign of some of these constants is determined and is found to be negative in either cc or ct pathways. The use of the "methyl replacement technique" shows a dominant σ electron contribution to the 4J coupling constants. In all examples studied here, the 4J coupling value is dependent on the pathway: 4Jct (−0.30 at −0.45 Hz) > 4Jcc (−0.10 at −0.15 Hz). The existence of a stereospecificity for this coupling is in accordance with a preponderant σ electron mechanism and is useful in conformational analysis of planar aromatic aldehydes.

1H and 19F NMR conformational studies of the monofluorostyrenes in solution. Comparison with theory and vapor phase behavior

1990 ◽  
Vol 68 (8) ◽  
pp. 1383-1392 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Side Chain ◽  
Coupling Constant ◽  
Mo Calculations ◽  
Carbon Carbon Bond ◽  
Electron Contribution ◽  
Internal Barriers ◽  
Cis And Trans ◽  
Coupling Mechanisms

The parameters for the high resolution 1H and 19F NMR spectra of 2-, 3-, and 4-fluorostyrene are reported for solutions in CS2 and acetone-d6 at 300 K. The populations of the planar cis and trans conformers of 2- and 3-fluorostyrene are deduced from the long-range coupling constants involving the meta and α protons. These populations are insensitive to solvent and appear to be in reasonable agreement with previous 6-31G MO computations for the free molecule; they are also compared with populations deduced from recent rotational and vibronic spectra. The long-range coupling constants for the protons of 4-fluorostyrene imply an internal barrier to rotation about the exocyclic carbon–carbon bond very similar to that in styrene, in agreement with the 6-31G results. The signs of the coupling constants involving 19F and the protons in the side chain are reported and discussed in terms of coupling mechanisms for the three molecules. An earlier surmise, of a positive a electron contribution to the coupling constant over six bonds in an all-trans arrangement, is confirmed for the meta and trans-β protons in 3-fluorostyrene. Keywords: monofluorostyrenes, 1H and 19F NMR, conformations, long-range coupling mechanisms, MO calculations of internal barriers.

Conformational dynamics detected by nuclear magnetic resonance NOE values and J coupling constants

1988 ◽  
Vol 110 (11) ◽  
pp. 3393-3396 ◽  
Author(s):  
Horst. Kessler ◽  
Christian. Griesinger ◽  
Joerg. Lautz ◽  
Arndt. Mueller ◽  
Wilfred F. Van Gunsteren ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Dynamics ◽  
Coupling Constants ◽  
J Coupling ◽  
J Coupling Constants ◽  
Nuclear Magnetic

Interpretation of cytidine proton chemical shifts and J coupling constants calculated by DFT

2006 ◽  
Vol 767 (1-3) ◽  
pp. 81-85 ◽  
Author(s):  
J.T. Fischer ◽  
S.G. Wehner ◽  
U.M. Reinscheid
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
J Coupling ◽  
J Coupling Constants ◽  
Proton Chemical Shifts

Proton Magnetic Resonance Spectra of Some Amphetamines and Related Compounds and Observations on Rotamer Populations

1971 ◽  
Vol 49 (19) ◽  
pp. 3143-3151 ◽  
Author(s):  
K. Bailey ◽  
A. W. By ◽  
K. C. Graham ◽  
D. Verner
Keyword(s):  
Hydrogen Bonding ◽  
Phenyl Ring ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Side Chain ◽  
Amino Group ◽  
Ortho Position ◽  
Electronic Effects ◽  
Related Compounds

Data from the p.m.r. spectra of β-amino-, β-aminohydrochloride-, β-hydroxy-, and β-nitro-α-phenyl-propanes having methyl or methoxy substituants on the phenyl ring (37 compounds in all) are presented. The α and β protons of the side-chain give a pattern usually analyzable as ABX. The data are discussed in terms of correlations of coupling constants and chemical shifts with electronegativity of the substituent groups, steric and electronic effects, and apparent changes in rotamer populations. Hydrogen-bonding between the amino group of amphetamines and a methoxyl function at the ortho position in the phenyl ring is indicated for the salts but not the free bases.

Fluorine detected 2D NMR experiments for the practical determination of size and sign of homonuclear F–F and heteronuclear C–F multiple bond J-coupling constants in multiple fluorinated compounds

2013 ◽  
Vol 231 ◽  
pp. 79-89 ◽  
Author(s):  
Ruud L.E.G. Aspers ◽  
Kirsten A.M. Ampt ◽  
Peter Dvortsak ◽  
Martin Jaeger ◽  
Sybren S. Wijmenga
Keyword(s):  
Multiple Bond ◽  
2D Nmr ◽  
Coupling Constants ◽  
J Coupling ◽  
J Coupling Constants

High-Resolution J-Scaling Nuclear Magnetic Resonance Spectra in Inhomogeneous Fields via Intermolecular Multiple-Quantum Coherences

2009 ◽  
Vol 63 (5) ◽  
pp. 585-590 ◽  
Author(s):  
Yanqin Lin ◽  
Zhong Chen ◽  
Shuhui Cai ◽  
Jianhui Zhong
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Chemical Shifts ◽  
Spin Systems ◽  
Coupling Constants ◽  
Multiple Quantum ◽  
J Coupling ◽  
Inhomogeneous Fields ◽  
J Coupling Constants

High-resolution nuclear magnetic resonance (NMR) spectroscopy with information on chemical shifts and J-coupling constants is a sensitive tool for studying physical, chemical, and biological properties of materials at the molecular level. In this paper, a pulse sequence is developed for acquiring high-resolution NMR spectra of liquid samples with J-scaling in inhomogeneous fields via two-dimensional intermolecular multiple-quantum coherence acquisitions. In the resulting one-dimensional projection spectra, apparent J-coupling constants were obtained with a scaling factor theoretically varying from zero (completely decoupled) to infinity relative to the original J-coupling constants while retaining information on chemical shifts, relative peak areas, and multiplet patterns. This allows either an accurate measurement of small J-coupling constants of weakly coupled spin systems or less crowded spectra for spin systems with J-splitting. Experimental observations and simulation results agree with theoretical analysis.

Through-space or proximate 19F,19F and 19F,1H spin–spin coupling constants in some benzenesulfonyl fluoride derivatives

1976 ◽  
Vol 54 (22) ◽  
pp. 3564-3568 ◽  
Author(s):  
William J. E. Parr ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Side Chain ◽  
Conformational Preference ◽  
Fluorine Nucleus ◽  
Spin Coupling Constants ◽  
The Difference ◽  
Spin Spin Coupling

The analysis of the fluorine and proton magnetic resonance spectra of 2,4,6-trimethylbenzenesulfonyl fluoride and of 2,5-difluorobenzenesulfonyl fluoride yields the signs and magnitudes of the spin–spin coupling constants containing a through-space component. The coupling between the fluorine nucleus and the methyl protons over five bonds is +1.9 Hz, opposite in sign to the −3.1 Hz observed for the corresponding coupling in 2,6-dimethylbenzoyl fluoride. The difference of 5 Hz is possibly a consequence of the different conformational preference of the SO2F and COF substituents. The coupling over four bonds between the fluorine nucleus on the side chain and that on the ring is +11.6 Hz in 2,5-difluorobenzenesulfonyl fluoride. It is argued that this value indicates a preference of the S—F bond for a plane lying, on average, nearly perpendicular to the benzene ring. Similar indications are noted for pentafluorobenzenesulfonyl fluoride and for pentafluorobenzenesulfinyl fluoride.

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