Effect of Solvent Upon the Vicinal Proton Coupling Constants of Complex Substituted Ethanes. II. Anomalous Results for 1-Phenyl-1,2,2-trihaloethanes

1971 ◽  
Vol 49 (8) ◽  
pp. 1209-1217 ◽  
Author(s):  
W. F. Reynolds ◽  
D. J. Wood
Keyword(s):  
Hydrogen Bonding ◽  
Solvent Effects ◽  
Coupling Constants ◽  
Electrostatic Model ◽  
Effect Of Solvent ◽  
Vicinal Coupling Constants ◽  
Proton Coupling ◽  
General Terms ◽  
Vicinal Proton

The n.m.r. spectra of 11 tetra-substituted ethanes have been obtained in a number of solvents. Changes in the vicinal coupling constants of 1-phenyl-1,2,2-trihaloethanes with solvent do not fit the electrostatic model for solvent effects. It is concluded that the theory breaks down because solute–solvent hydrogen bonding specifically favors the trans rotamers of these compounds. The conditions under which the theory would be expected to break down are also discussed in more general terms.

Effect of Solvent Upon the Vicinal Proton Coupling Constants of Complex Substituted Ethanes. III. 1,2-Dihaloalkanes

1971 ◽  
Vol 49 (21) ◽  
pp. 3438-3442 ◽  
Author(s):  
D. A. Dawson ◽  
W. F. Reynolds
Keyword(s):  
Long Range ◽  
Conformational Changes ◽  
Coupling Constants ◽  
Effect Of Solvent ◽  
Vicinal Coupling Constants ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
The Difference

The n.m.r. spectra of eight 1,2-dihaloalkanes have been determined in solvents of differing polarity. The relative rotamer stabilities for each compound have been deduced from the variation of the difference and sum of vicinal coupling constants with solvent. Variations in geminal and long range coupling constants with solvent are also attributed to conformational changes.

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.

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.

Solvent effects on the proton spectra of some halopropenes. The preparation and proton resonance spectra of the 1-iodopropenes

1967 ◽  
Vol 45 (10) ◽  
pp. 1081-1087 ◽  
Author(s):  
F. Hruska ◽  
D. W. McBride ◽  
T. Schaefer
Keyword(s):  
Hydrogen Bonding ◽  
Solvent Effects ◽  
Olefinic Proton ◽  
Coupling Constants ◽  
Proton Resonance ◽  
Methyl Proton ◽  
Reaction Field ◽  
Field Effects ◽  
Proton Coupling ◽  
Solvent Shifts

The preparation and proton resonance spectra of the 1-iodopropenes are reported and solvent effects on the proton spectra of the chloro-, bromo-, and iodo-compounds are measured. The proton coupling constants are discussed in terms of old and new electronegativity correlations. The olefinic cis and trans proton shifts can be attributed mainly to a paramagnetic contribution from the substituent, whereas the gem olefinic proton shifts depend in addition on the electron-withdrawing power of the substituent. The methyl proton shifts in the 1-substituted compound show little dependence on the substituent and this is discussed in relation to the barrier heights to methyl rotation. The solvent shifts in benzene cannot be completely reconciled with a dipole – induced dipole model. They increase with the size of the substituent and are largest for protons farthest from the substituent. The solvent shifts in acetone can be explained as due to weak hydrogen bonding and reaction field effects. The shifts of protons gem to the substituent arise mainly from hydrogen bonding, whereas the shifts of protons cis or trans have significant contributions from both effects. The reaction field effects can also account for the methyl shifts in acetone.

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
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