RELATIVE SIGNS OF GEMINAL AND VICINAL PROTON–PROTON COUPLING CONSTANTS IN α,β-DIPHENYLPROPIONIC ACID AND ITS METHYL ESTER

1962 ◽  
Vol 40 (8) ◽  
pp. 1483-1489 ◽  
Author(s):  
Robert R. Fraser
Keyword(s):  
Methyl Ester ◽  
Opposite Sign ◽  
Coupling Constants ◽  
Proton Proton ◽  
Vicinal Coupling Constants ◽  
Proton Coupling ◽  
Vicinal Proton

It has been shown that the geminal and vicinal coupling constants are of opposite sign in α,β-diphenylpropionic acid and its methyl ester. The significance of the results is discussed.

Notiz: The Dependence of Vicinal Proton-Proton Coupling Constants of Norbomenes on Molecular Structure

1996 ◽  
Vol 51 (9) ◽  
pp. 1042-1044
Author(s):  
Zoran Marković ◽  
Stanimir Konstantinović ◽  
Ivan Gutman
Keyword(s):  
Molecular Structure ◽  
Standard Deviation ◽  
Structural Factor ◽  
Coupling Constants ◽  
Proton Proton ◽  
Vicinal Coupling Constants ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
New Equation ◽  
Mutually Independent

Abstract A modification of the Karplus equation, containing four mutually independent structural terms and five adjustable parameters, is put forward. The new structural factor, introduced into this modification is sin (θ1 + θ2)/2. The new equation reproduces experimental NMR vicinal coupling constants of norbornenes with a standard deviation of about 0.45 Hz.

The Dependence of Vicinal Proton-Proton Coupling Constants on Molecular Structure

1994 ◽  
Vol 49 (7-8) ◽  
pp. 815-818
Author(s):  
Zoran Marković ◽  
Stanimir Konstantinović ◽  
Ivan Gutman
Keyword(s):  
Molecular Structure ◽  
Standard Deviation ◽  
Substituent Effect ◽  
Coupling Constants ◽  
Proton Proton ◽  
Vicinal Coupling Constants ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
New Equation ◽  
Mutually Independent

Abstract A modification of the Karplus equation is put forward, containing for mutually independent structural terms and four adjustable parameters. Among the new factors introduced in this modifi­cation are the distance between protons and Muallay's group electronegativity, used in the evalua­tion of the α-substituent effect. The new equation reproduces experimental NMR vicinal coupling constants with a standard deviation of about 0.6 Hz.

Proton magnetic resonance study of the conformation of the pyrrolidine ring in some proline-thiohydantoins

1988 ◽  
Vol 53 (11) ◽  
pp. 2503-2510 ◽  
Author(s):  
Jef J. M. Sleeckx ◽  
Marc J. O. Anteunis ◽  
Frans A. M. Borremans
Keyword(s):  
Present Model ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Proton Magnetic Resonance Study ◽  
Vicinal Proton ◽  
Different Temperatures ◽  
Experimental Justification ◽  
State Assumption ◽  
Methyl Phenyl

The conformational behaviour of a series of N-substituted thiohydantoins of proline was studied by proton NMR. The pseudorotational parameters of the proline moiety were calculated from the ten vicinal proton-proton coupling constants assuming a two state equilibrium (N ⇋ S). The effect of the different substituents (methyl, phenyl, para-nitrophenyl) at the thiohydantoin nitrogen on the conformation of the pyrrolidine rings is discussed. The spectra of proline-N-methylthiohydantoin were recorded at different temperatures in octadeuterotoluene solution. The conformational analysis of these spectra showed that the ratio of the populations of the N and S forms changes considerably with temperature, while the conformational identity of both the N and S forms remains strictly preserved. These facts provide an additional experimental justification of the two-state assumption, at least so for the present model compounds.

Vicinal proton—proton coupling constants. Basis set dependence in SCF ab initio calculations

1993 ◽  
Vol 206 (1-4) ◽  
pp. 253-259 ◽  
Author(s):  
Jesús San-Fabián ◽  
Joaquín Guilleme ◽  
Ernesto Díez ◽  
Paolo Lazzeretti ◽  
Massimo Malagoli ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Basis Set ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Vicinal proton–proton coupling constants: MCSCF ab initio calculations of ethane

1999 ◽  
Vol 314 (1-2) ◽  
pp. 168-175 ◽  
Author(s):  
J. Guilleme ◽  
J. San Fabián ◽  
J. Casanueva ◽  
E. Dı́ez
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Vicinal proton-proton coupling constants

1994 ◽  
Vol 82 (5) ◽  
pp. 913-928 ◽  
Author(s):  
Jesús San-Fabián ◽  
Joaquín Guilleme ◽  
Ernesto Díez ◽  
Paolo Lazzeretti ◽  
Massimo Malagoli ◽  
...  
Keyword(s):  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Analysis of vicinal proton-proton coupling constants in polypropylene chains

1981 ◽  
Vol 14 (6) ◽  
pp. 1830-1831 ◽  
Author(s):  
Dino R. Ferro ◽  
Massimo Ragazzi
Keyword(s):  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Conformation of purine mononucleotides by H{H} and P{H} nuclear Overhauser effects

1983 ◽  
Vol 61 (7) ◽  
pp. 1456-1464 ◽  
Author(s):  
H. Santos ◽  
A. V. Xavier ◽  
C.F.G.C. Geraldes
Keyword(s):  
Aqueous Solution ◽  
Nuclear Overhauser Effect ◽  
Coupling Constants ◽  
Glycosidic Bond ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Group A ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects

The proton–proton and phosphorus–proton nuclear Overhauser effect (nOe) of guanosine 5′-monophosphate (5′-GMP) was measured in aqueous solution at different pH values and in the presence of excess LaIII at acid pH. These data and nOe data from the literature for other mononucleotides were used together with vicinal proton–proton coupling constants to investigate the conformations of mononucleotides in aqueous solution, especially their rotational state about the glycosidic bond. Comparison of observed and calculated enhancements using various conformational models for the glycosidic bond gave predominantly anti conformations for 5′-AMP and 5′-GMP and a mixture of syn and anti conformations for 2′-AMP, 2′-GMP, 3′-AMP, and 3′-GMP. Protonation of 5′-GMP at N-7 of the guanine base alters the amplitude of its torsion angle within the anti range. The agreement between the glycosidic nucleotide conformations defined by nOe and by the lanthanide probe method is good but not perfect. As complexation of 5′-GMP with LaIII through the phosphate group has only a small effect on the conformation of its exocyclic group, a comparison of the two methods is justified.

Prediction ofanti andgauche vicinal proton-proton coupling constants in carbohydrates: A simple additivity rule for pyranose rings

1980 ◽  
Vol 13 (6) ◽  
pp. 417-429 ◽  
Author(s):  
Cornelis Altona ◽  
Cornelis A. G. Haasnoot
Keyword(s):  
Coupling Constants ◽  
Additivity Rule ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Non-equivalence of vicinal proton–fluorine coupling constants in a CF3—CH2 group

1967 ◽  
Vol 45 (13) ◽  
pp. 1485-1489 ◽  
Author(s):  
Robert R. Fraser ◽  
Paul Hanbury
Keyword(s):  
Unique Feature ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Anomeric Effect ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Different Temperatures ◽  
Tetrahydropyranyl Ether

The proton magnetic resonance spectrum of the tetrahydropyranyl ether of 2,2,2-trifluoroethanol has been measured in several solvents and at different temperatures. Analysis of the ABX3 pattern produced by the trifluoroethyl group revealed a unique feature. Under all conditions, it was found that the vicinal coupling constants JAX and JBX had different magnitudes. This non-equivalence is interpreted as evidence that the C—HA and C—HB bonds of the trifluoroethyl group differ electronically. A possible relation between this finding and the anomeric effect is discussed. In contrast to the above results, the tetrahydropyranyl ether of ethanol showed equal vicinal proton–proton coupling constants in the ethyl group.

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