A linear correlation of aromatic substituent effects with geminal coupling constants

1967 ◽  
Vol 45 (21) ◽  
pp. 2489-2491 ◽  
Author(s):  
Richard W. Franck ◽  
Joseph Auerbach
Keyword(s):  
Linear Correlation ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Asymmetric Center ◽  
Proton Proton ◽  
Aromatic Substituent ◽  
Benzyl Alcohols ◽  
Proton Coupling ◽  
Geminal Coupling ◽  
Hammett Σ Constants

A linear correlation of the geminal coupling constants of benzylic protons with the Hammett σ constants has been observed. The proton–proton coupling was made observable by preparing the tetrahydropyranyl ethers of benzyl alcohols. The introduction of the asymmetric center caused the benzyl protons to become non-equivalent. The observed correlation serves as an additional confirmation of the Pople and Bothner-By theory of geminal coupling.

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.

The Molecular Structure of Allenes and Ketenes, XII [1] Four-Bond Proton-Proton Spin-Spin Couplings in Allenes

1978 ◽  
Vol 33 (8) ◽  
pp. 932-936 ◽  
Author(s):  
Wolfgang Runge
Keyword(s):  
Molecular Structure ◽  
Charge Transfer ◽  
Quantum Chemical ◽  
Substituent Effects ◽  
Proton Spin ◽  
Coupling Constants ◽  
Proton Proton ◽  
Resonance Effects ◽  
Proton Coupling ◽  
Parameter Approach

Abstract Four-bond proton-proton coupling constants in allenes are reported. The substituent effects on the coupling constants are discussed on the basis of the dual-substituent parameter approach. Furthermore, the coupling constants are related to quantum-chemical indices (electron densities, overlap populations) obtained from semiempirical CNDO/S and ab initio STO-3G calculations.The magnitudes of the coupling constants depend upon the polar natures of the substituents as well as upon their charge-transfer abilities (resonance effects) to a com-parable amount.In general, the coupling constants in 1,3-disubstituted allenes are nonadditive in ligand -specific parameters.

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.

Additivity of substituent effects on the proton–proton coupling constants in substituted benzenes. Investigation of some trisubstituted benzenes

1968 ◽  
Vol 46 (15) ◽  
pp. 2531-2534 ◽  
Author(s):  
T. Schaefer ◽  
G. Kotowycz ◽  
H. M. Hutton ◽  
J. W. S. Lee
Keyword(s):  
Root Mean Square ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Mean Square ◽  
Polar Solvents ◽  
Substituted Benzenes ◽  
Proton Proton ◽  
Temperature Range ◽  
Proton Coupling ◽  
Saturation Effects

An additivity scheme based on the changes in ortho, meta, and para proton coupling constants of benzene induced by a single substituent is applied to a number of trisubstituted benzenes. Ortho coupling constants are well reproduced (root mean square deviations = 0.05 c.p.s.) by the scheme but for meta and para couplings saturation effects are indicated. For the latter two couplings there are two substituents ortho to one of the protons involved. Measurements indicate that a temperature range of 100 °C has a negligible effect on the couplings but that polar solvents are to be avoided in obtaining data for the testing of additivity schemes.

Transoid Homoallylic Proton-Proton Coupling Constants

1989 ◽  
Vol 42 (5) ◽  
pp. 659 ◽  
Author(s):  
M Barfield ◽  
RJ Spear ◽  
S Sternhell
Keyword(s):  
Angular Dependence ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Mo Calculations ◽  
Proton Proton ◽  
Proton Coupling ◽  
Tentative Assignment ◽  
Single Compound ◽  
Derivatives Of

Transoid homoallylic coupling constants (5JH,H) for six compounds (5,10-dihydroindeno[2,1-alindene and confertifolin derivatives) of fixed stereochemistry were determined and compared with calculated values. Magnetic equivalence limited discrete determination of 5Jtrans and 5Jcis to three of these compounds. The single compound where unequivocal assignment could be made revealed 5Jtrans > 5Jcis; this was supported in two other compounds by tentative assignment. Changes in the magnitude of the couplings suggested that substantial substituent effects may be operative. INDO-MO calculations correctly predicted the angular dependence but incorrectly predicted 5Jcis > 5Jtrans.

A comparison of substituent effects on vicinal proton–proton and carbon–proton coupling constants

1977 ◽  
Vol 55 (21) ◽  
pp. 3686-3688 ◽  
Author(s):  
T. P. Forrest ◽  
S. Sukumar
Keyword(s):  
Substituent Effects ◽  
Coupling Constants ◽  
Proton Proton ◽  
Tert Butyl ◽  
Proton Coupling ◽  
Regular Change ◽  
Vicinal Proton ◽  
The Relationship

Vicinal carbon–proton coupling constants have been determined for a series of tert-butyl derivatives and compared to the vicinal proton–proton coupling constants in the analogous series of isopropyl derivatives. In both series coupling constants were found to decrease with electronegativity of substituent, with 3JC,H decreasing more rapidly than 3JH,H. The relationship between the two types of coupling was found to be JC,H = 1.2JH,H − 3.5. The regular change in the ratio of JC,H to JH,H indicates that substituent effects can be useful in predicting carbon–proton coupling constants from proton–proton models.

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.

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