CORRELATION OF ETHYLENIC PROTON COUPLING CONSTANTS WITH THE ELECTRONEGATIVITY OF SUBSTITUENTS INTERPRETATION OF THE DEVIATIONS OF BROMO AND IODO SUBSTITUENTS

1965 ◽  
Vol 43 (10) ◽  
pp. 2827-2833 ◽  
Author(s):  
F. Hruska ◽  
G. Kotowycz ◽  
T. Schaefer
Keyword(s):  
Linear Relationship ◽  
Coupling Constants ◽  
Box Model ◽  
Coupling Constant ◽  
Vinyl Bromide ◽  
Proton Coupling ◽  
Vinyl Iodide ◽  
Cis And Trans

It is shown that for the geminal, cis and trans proton coupling constants in vinyl bromide and vinyl iodide there exist significant deviations from an inverse linear relationship between coupling constants and the electronegativity of the substituent in monosubstituted ethylenes. By an adaptation of the box model of Juan and Gutowsky to the 13C—H coupling constants in the system CH2 = CHX, it is shown that there are related anomalies in the 13C—H coupling constants in vinyl bromide and vinyl iodide. A comparison of the three types of 13C—H coupling constants in some vinyl compounds suggests that there may be an interaction between the substituent and the C—H bond which affects the coupling constant but not the s-character of the carbon orbital in the bond.

SOLVENT EFFECTS AS AN AID IN THE ANALYSIS OF THE PROTON MAGNETIC RESONANCE SPECTRUM OF VINYL BROMIDE

1960 ◽  
Vol 38 (11) ◽  
pp. 2066-2073 ◽  
Author(s):  
T. Schaefer ◽  
W. G. Schneider
Keyword(s):  
Chemical Shift ◽  
Solvent Effects ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Vinyl Bromide ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Cis And Trans

By making use of specific solvent effects it has been possible to vary the relative chemical shift between the geminal protons of vinyl bromide from about +10 cycles/sec to −4 cycles/sec (at 60 Mc/sec) and to study the resultant changes in the proton resonance spectrum in the limiting region of zero chemical shift. Of particular interest is the growth and displacement of the combination lines, which appear in the resonance signals of the proton bonded to the same carbon atom as the bromine. From the variation of the six possible lines in this region it was confirmed that the cis and trans proton coupling constants must have the same sign. The intensity distribution of the lines in the geminal proton region require the geminal coupling constant to be of opposite sign to the other two.

Concerning a relationship between long-range ring proton – methyl proton coupling constants and mobile bond order

1968 ◽  
Vol 46 (4) ◽  
pp. 654-656 ◽  
Author(s):  
D. J. Blears ◽  
S. S. Danyluk ◽  
T. Schaefer
Keyword(s):  
Linear Relationship ◽  
Long Range ◽  
Bond Order ◽  
Coupling Constants ◽  
Methyl Proton ◽  
Methyl Group ◽  
Potential Barriers ◽  
Proton Coupling ◽  
Induced Changes ◽  
Excitation Parameters

Long-range proton – methyl proton coupling constants in propene, mesitylene, 9-methylphenanthrene, and acenaphthene appear to be linearly related to the square of the mobile bond order between the carbon atoms bonded to the methyl group and the proton. However, substituent-induced changes in the charge on and hybridization state of the carbon atoms, in excitation parameters and in potential barriers to rotation of the methyl group, may also affect the coupling. Such changes must be considered in the application of a possible linear relationship.

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.

C13 SPLITTINGS IN SOME SUBSTITUTED BENZENES

1962 ◽  
Vol 40 (9) ◽  
pp. 1758-1762 ◽  
Author(s):  
H. M. Hutton ◽  
W. F. Reynolds ◽  
T. Schaefer
Keyword(s):  
Long Range ◽  
Electron Acceptors ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Substituted Benzenes ◽  
First Order ◽  
Proton Coupling

C13 sidebands in the proton spectra of some symmetrically substituted benzenes have been used to obtain carbon–hydrogen coupling constants as well as proton coupling constants.A long-range carbon–hydrogen coupling constant has also been found. Substituents which act as electron acceptors in an inductive manner are found to increase the C13H coupling constants by as much as 20 c.p.s. The patterns of the sidebands are discussed and possible errors in first-order analyses are indicated.

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 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.

Flavan derivatives. XVI. Acid-catalysed reactions of secondary benzyl alcohols and 1-tetralols in methanol

1967 ◽  
Vol 20 (10) ◽  
pp. 2137 ◽  
Author(s):  
JW Clark-Lewis ◽  
V Nair
Keyword(s):  
Acetic Acid ◽  
Hydrogen Chloride ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Dibenzyl Ether ◽  
Proton Coupling ◽  
Spin Coupling Constants ◽  
Acid Catalysed Reactions ◽  
Cis And Trans ◽  
Spin Spin Coupling

Under solvolytic conditions I-phenylpropan-1-01 and its p-methyl and p-methoxy derivatives gave 1 -arylprop- 1 -enes. 1 -(3,4-Dimethoxypheny1)propan- 1-01 behaved similarly, but in addition gave the known propene dimer di-isohomogenol (di-isoeugenol dimethyl ether). Ring-proton coupling constants (J 7.3 and 9.2 CIS) appear consistent with a staggered trans-trans-configuration for this dimer,$ in agreement with earlier interpretations of chemical evidence. 1-(2,4,6-Trimethoxy- pheny1)propan-1-01 proved very reactive and gave the symmetrical dibenzyl ether under very mild acid catalysis, but with higher acid concentration it gave the prop-1-ene accompanied by a 1,l-diarylpropane formed by electrophilic displace- ment of the propan-1-01 side-chain. Tetralin-1-01 and cis- and trans-tetralin-1,2-diols, which lack activating aromatic substituents, were stable towards methanolic acetic acid (3%) or hydrogen chloride (3%). 6-Methoxytetralin-1-01, however, gave 1,6-dimethoxytetralin with methanolic 0.001% acetic acid, but with higher tetra101 concentration it gave the symmetrical bis-tetralyl ether. 6-Methoxytetralin-1-01 gave 3,4-dihydro-6-methoxynaphthalene and its known dimer when heated with methanolic hydrogen chloride (1%). Nuclear magnetic resonance showed that the tetralins are conformationally mobile, and the spectra were consistent with rapid interconversion of two half-chair conformations. 3-Phenyltetralin-1-01 (tetralin analogue of flavan-3-01) was obtained in the l,3-cis-form and existed in the confor- mationally stable half-chair form with both substituents equatorial. Spin-spin coupling constants of cis- and trans-carbonates of tetralin-1,2-diols are close to values recorded for their flavandiol analogues.

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.

INDO MO Calculations of the Conformational Dependence of the vicinal 13C,H Spin–Spin Coupling Constant in Propane

1972 ◽  
Vol 50 (16) ◽  
pp. 2710-2712 ◽  
Author(s):  
R. Wasylishen ◽  
T. Schaefer
Keyword(s):  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Theory ◽  
Coupling Constant ◽  
Mo Calculations ◽  
Orbital Theory ◽  
Angle Dependence ◽  
Proton Coupling ◽  
Fermi Contact ◽  
Spin Spin Coupling

Molecular orbital theory at the INDO level of approximation is used to calculate the Fermi contact contribution to three-bond carbon–proton coupling constants in propane. The calculations predict a dihedral angle dependence of 3J(13C,H) in the 13C—C—C—H fragment similar to that observed for 3J(H,H), 3J(19F,H), and for 3J(31P,H) in the saturated X—C—C—H fragments.

Long-range spin–spin coupling constants between ring protons and aldehydic protons in some para-substituted benzaldehydes

1969 ◽  
Vol 47 (21) ◽  
pp. 4005-4010 ◽  
Author(s):  
S. S. Danyluk ◽  
C. L. Bell ◽  
T. Schaefer
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Proton Proton ◽  
Proton Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Coupling Mechanisms ◽  
Benzaldehyde Derivatives

The long-range proton–proton coupling constants between the ring protons and the aldehydic proton are reported for a series of para-substituted benzaldehyde derivatives. It was found that JoH,CHO < 0 and JmH,CHO > 0. Furthermore, JoH,CHO increases in magnitude as the electron donating power of the sub-stituent increases. A similar trend is observed forJmH,CHO but the ratio of the increase to the magnitude of JmH,CHO is much less than for JoH,CHO. A good correlation is obtained between JoH,CHO and the sub-stituent parameters of Swain and Lupton.The coupling constant data are discussed in terms of σ and π coupling mechanisms and it is concluded that σ electron mechanisms are dominant for both JoH,CHO and JmH,CHO.

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