Geminal Proton‐Proton Coupling Constant

1965 ◽  
Vol 43 (9) ◽  
pp. 3402-3403 ◽  
Author(s):  
P. Loève ◽  
L. Salem
Keyword(s):  
Coupling Constant ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton

The effect of substituents on geminal proton–proton coupling constants. III

1977 ◽  
Vol 55 (14) ◽  
pp. 2642-2648 ◽  
Author(s):  
Roger N. Renaud ◽  
John W. Bovenkamp ◽  
Robert R. Fraser ◽  
Raj Capoor
Keyword(s):  
Coupling Constants ◽  
Coupling Constant ◽  
Mo Calculations ◽  
Proton Proton ◽  
Effect Of Substituents ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
The Difference ◽  
Methylene Group

The effect of substituents at the 3-position in a series of N-methyl 5,6-dihydro-7H,12H-di-benzo[c,f]azocines on the geminal coupling constants of the C-12 methylene protons has been determined. The slope of the Hammett plot of 2J vs. σ has been found to be +0.20. The orientation of the methylene protons with respect to the π orbitals of the benzene ring bearing the substituent is such that no hyperconjugative effect should be present. The value of +0.20 is in contrast to a previously measured slope of −1.9 for compounds having a geometry ideal for hyperconjugative effects and substantiates the predictions of theoretical MO calculations. As a result, the reliability of this conformational dependence of ρ for use in conformational analysis has been strengthened.A comparison of the data for the azocines with those in the literature indicates the difference between the minimum and maximum effects of a phenyl substituent on a geminal coupling constant of an attached methylene group is 5.5 Hz.

The effect of substituents on geminal proton–proton coupling constants

1967 ◽  
Vol 45 (21) ◽  
pp. 2481-2487 ◽  
Author(s):  
Robert R. Fraser ◽  
Paul Hanbury ◽  
C. Reyes-Zamora
Keyword(s):  
Resonance Spectrum ◽  
Coupling Constants ◽  
Molecular Orbital Theory ◽  
Coupling Constant ◽  
Orbital Theory ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Methylene Group

A series of 2-benzyloxytetrahydropyrans bearing substituents at the ortho, meta, and para positions of the benzene ring have been synthesized. From the nuclear magnetic resonance spectrum of each compound, the geminal coupling constant (J) between the non-equivalent protons of the benzylic methylene group was determined. The geminal coupling constant for the methylene group of several benzyl sulfoxides was also measured. In the ether series it was found that J varied from 11.1 to 13.3 c.p.s. and was directly proportional to the Hammett σ value for the meta and para substituents. In the sulfoxides, however, J was unaffected by the substituent. On the basis of the molecular orbital theory of geminal coupling constants and steric considerations, it is proposed that the sensitivity of J to the substituent effect is dependent upon the conformation of the molecules with respect to the Ar—CH2 bond. The potential utility of this relation as a method of conformational analysis is discussed.

Studies on the PMR Spectra of Oxetanes. VI 2-(3-Chlorophenyl)oxetane and 2-(2-Chlorophenyl)oxetane at 60 and 100 MHz

1974 ◽  
Vol 29 (12) ◽  
pp. 1902-1906 ◽  
Author(s):  
Jukka Jokisaari
Keyword(s):  
Long Range ◽  
Chemical Shifts ◽  
Methine Proton ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Proton Proton ◽  
Temperature Range ◽  
Proton Coupling ◽  
Phenyl Proton ◽  
Pmr Spectra

The 100 MHz spectra of the phenyl protons in 2-(3-chlorophenyl) oxetane and 2-(2-chlorophenyl) oxetane have been analysed. The 60 MHz PMR chemical shifts and proton-proton coupling constants have been studied in the temperature range from -20 C to +80 °C. The chemical shifts were sensitive to temperature, while the coupling constants were not, except the long range 5Jm coupling constant between the methine proton and the meta positioned phenyl proton in 2-(2-chlorophenyl) oxetane.

Concerning the conformational distribution in isopropylcyclopropane

1982 ◽  
Vol 60 (7) ◽  
pp. 845-847 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Roderick E. Wasylishen
Keyword(s):  
Methine Proton ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
Trans Conformer ◽  
Partial Analysis ◽  
Vicinal Proton ◽  
Conformational Distribution

A partial analysis of the 400 MHz 1H nmr spectrum of isopropylcyclopropane yields 8.6 ± 0.2 Hz for the vicinal proton–proton coupling constant between a cyclopropyl proton and the methine proton of the isopropyl group. The fractional population of the s-trans conformer is estimated as 0.65 ± 0.l0 at 300 K, in reasonable agreement with molecular mechanics and INDO MO computations of the energies of the gauche and trans forms.The conformational preference of this molecule is similar to that in n-butane and in vinylcyclopropane but contrasts with that in biisopropyl and bicyclopropyl.

Geminal Proton-Proton Coupling Constants in CH2[UNK]N-- Systems

1963 ◽  
Vol 85 (24) ◽  
pp. 4041-4042 ◽  
Author(s):  
B. L. Shapiro ◽  
S. J. Ebersole ◽  
G. J. Karabatsos ◽  
F. M. Vane ◽  
S. L. Manatt
Keyword(s):  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton

Substituent effects on geminal proton–proton coupling constants

1970 ◽  
Vol 48 (13) ◽  
pp. 2134-2138 ◽  
Author(s):  
Y. L. Chow ◽  
S. Black ◽  
J. E. Blier ◽  
M. M. Tracey
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Hammett Σ Constants

The geminal coupling constants between the non-equivalent benzylic protons of a series of para- and meta-substituted N-benzyl-2-methylpiperidines were shown to be proportional to the Hammett σ constants of the substituents with ρ −1.38 in carbon tetrachloride, −1.21 in benzene, and nearly 0 in 1 N DCl solutions. The ρ values were compared with those of other series and were discussed in terms of the possible conformations involved. The chemical shifts of the benzylic protons of the piperidine derivatives did not give a good correlation with the Hammett σ constants in these solvents.

An 1H NMR conformational analysis of 3-phenylpentane in solution

1993 ◽  
Vol 71 (4) ◽  
pp. 520-525 ◽  
Author(s):  
Ted Schaefer ◽  
Lina B.-L. Lee
Keyword(s):  
Alkyl Chain ◽  
Chemical Shifts ◽  
Close Approach ◽  
Solvent Mixture ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Proton Proton ◽  
Vicinal Coupling Constants ◽  
Proton Coupling ◽  
Proton Chemical Shifts

Some 30 proton chemical shifts and proton–proton coupling constants are reported for a 4.7 mol% solution of 3-phenylpentane in a CS2/C6D12/TMS solvent mixture at 300 K. The long-range coupling constant over six formal bonds between the methine and para protons is used to deduce an apparent twofold barrier of 15.0 ± 0.3 kJ/mol to rotation about the Csp2—Csp3 bond, at least twice as large as that for isopropylbenzene in solution. AM1 computations agree with experiment in finding the conformation of lowest energy as that in which the methine C—H bond is situated in the phenyl plane, but predict a barrier height of only 13.9 kJ/mol. The vicinal coupling constants are consistent with a fractional population, 0.38(2), of the TT conformer, that in which all the carbon atoms of the alkyl chain lie in a plane. A doubly degenerate conformer, TG+(G−T), in which one methyl group is twisted away from the phenyl substituent, then has a fractional population of 0.62(2). The assumption that only these three conformers are present is tested with the signs and magnitudes of the four different coupling constants over four bonds. These coupling constants are consistent with the absence of significant proportions of the other six all-staggered conformers. These six are characterized by a close approach of the methyl groups (1,5 interactions) or by proximity of the methyl and phenyl moieties.

The relationship between carbon-13 substituent chemical shifts and proton coupling constants in aza-aromatic systems

1984 ◽  
Vol 37 (2) ◽  
pp. 311 ◽  
Author(s):  
IB Cook ◽  
S Pengprecha ◽  
B Ternai
Keyword(s):  
Experimental Data ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Proton Proton ◽  
Proton Coupling ◽  
Substituted Pyridines ◽  
Aromatic Systems ◽  
The Relationship

An equation which relates the ortho carbon-13 substituent chemical shift α-SCS in aza-aromatics to the ortho proton-proton coupling constant 3J(HH) in the corresponding carbocyclic compound is derived from experimental data. The implications for N-N bond fixation in diaza-aromatics are discussed. When the equation is applied to 2-substituted pyridines, an electronegativity parameter must be included to explain the results.

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