Signs of long-range amino proton – ring proton coupling constants in N-ethyl-4-chloro-2-nitroaniline

1970 ◽  
Vol 48 (8) ◽  
pp. 1343-1345 ◽  
Author(s):  
T. Schaefer ◽  
R. Wasylishen
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Proton Resonance ◽  
Ring Proton ◽  
Multiple Resonance ◽  
Proton Coupling ◽  
Spin Spin Coupling

In N-ethyl-4-chloro-2-nitroaniline there exists a measurable indirect spin–spin coupling constant of ±0.39 ± 0.03 Hz between the methylene protons and ring proton 6. The amino proton is coupled to ring protons 5 and 6 and also to the methylene protons. Consequently, although the amino proton resonance is broad due to incompletely relaxed coupling to 14N, normal multiple resonance experiments show that 5JmH,NH = 0.67 ± 0.03 Hz and 4JoH,NH = −0.35 ± 0.03 Hz.

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.

An estimate of the spin–spin coupling constant, 1J(1H,13C), in gaseous benzene

1996 ◽  
Vol 74 (8) ◽  
pp. 1524-1525 ◽  
Author(s):  
Ted Schaefer ◽  
Guy M. Bernard ◽  
Frank E. Hruska
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Dielectric Constant ◽  
Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Gaseous Benzene

An excellent linear correlation (r = 0.9999) exists between the spin–spin coupling constants 1J(1H,13C), in benzene dissolved in four solvents (R. Laatikainen et al. J. Am. Chem. Soc. 117, 11006 (1995)) and Ando's solvation dielectric function, ε/(ε – 1). The solvents are cyclohexane, carbon disulfide, pyridine, and acetone. 1J(1H,13C)for gaseous benzene is predicted to be 156.99(2) Hz at 300 K. Key words: spin–spin coupling constants, 1J(1H,13C) for benzene in the vapor phase; spin–spin coupling constants, solvent dielectric constant dependence of 1J(1H,13C) in benzene; benzene, estimate of 1J(1H,13C) in the vapor; nuclear magnetic resonance, estimate of 1J(1H,13C) in gaseous benzene.

Signs of spin–spin coupling constants between aldehydic and ring protons in 2,6-dinitrobenzaldehyde. Evidence for a hyperconjugative contribution to JpH,CHO

1969 ◽  
Vol 47 (19) ◽  
pp. 3529-3533 ◽  
Author(s):  
C. L. Bell ◽  
S. S. Danyluk ◽  
T. Schaefer
Keyword(s):  
Aldehyde Group ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Para Position ◽  
Steric Interaction ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The spin–spin coupling constant between the aldehydic proton and the proton in the para position, JpH,HCO is negative in 2,6-dinitrobenzaldehyde. JpH,CHO is also very likely negative in 2,6-dichlorobenzaldehyde. It is suggested that steric interaction with the ortho substituents forces the aldehyde group out of a coplanar conformation and leads to an interaction of the aldehydic C–H bond with the π system of the ring. Tentative values of θ, a measure of the deviation from coplanarity, are given.

Unusual behaviour of the spin–spin coupling constant 1JCH upon formation of CH⋯X hydrogen bond

2020 ◽  
Vol 22 (4) ◽  
pp. 1994-2000
Author(s):  
Elena Yu. Tupikina ◽  
Gleb S. Denisov ◽  
Alexander S. Antonov ◽  
Peter M. Tolstoy
Keyword(s):  
Hydrogen Bond ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Interatomic Distances ◽  
Unusual Behaviour ◽  
Spin Spin Coupling

One-bond coupling constants 1JXY are usually used as a measure of the corresponding X⋯Y interatomic distances.

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.

Nuclear magnetic resonance study of carbethoxypyrroles

1970 ◽  
Vol 48 (14) ◽  
pp. 2303-2305 ◽  
Author(s):  
M. W. Roomi ◽  
H. Dugas
Keyword(s):  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Ring Proton ◽  
Proton Coupling ◽  
Low Field ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The chemical shifts and the ring proton coupling constants of various substituted carbethoxypyrroles are reported.The electron-withdrawing effect of the carbethoxy groups shifts the resonances of the ring substituents to low field while the inductive and mesomeric effects of the methyl groups shift the resonances to higher field. The deshielding effect is more pronounced with 2-carbethoxypyrroles than for 3-carbethoxypyrroles. The ring proton spin–spin coupling constants depend on the nature of substituents and increase with the electronegativity of the substituents. In some cases long-range coupling between the methyl side-chain protons and ring protons could be observed.

The conformational distribution of 2-cyanobenzaldehyde and 3-cyanobenzaldehyde in solution and in the vapor

1991 ◽  
Vol 69 (7) ◽  
pp. 1039-1046 ◽  
Author(s):  
Ted Schaefer ◽  
Kerry J. Cox ◽  
Rudy Sebastian
Keyword(s):  
Long Range ◽  
Dipole Moments ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Orbital Theory ◽  
Spectral Parameters ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
Spin Spin Coupling

The 1H nuclear magnetic resonance spectra of 2-cyanobenzaldehyde (2CNB) and 3-cyanobenzaldehyde (3CNB) in CS2/C6D12 and acetone-d6 solutions at 300 K yield precise stereospecific long-range proton–proton coupling constants. These are used to establish the conformational population of the o-cis and o-trans conformers of these relatively polar molecules. For example, the fractional o-cis population of 2CNB changes from 0.12(4) in CS2/C6D12 to 0.46(6) in acetone-d6, whereas that of 3CNB is 0.48(2) in both solvents. Extrapolation to the vapor phase, using a dielectric model, implies a negligible concentration of the o-cis conformer of 2CNB and a roughly 50% abundance of each conformer of 3CNB. Computations at various levels of molecular orbital theory provide estimates of the rotational barrier of the aldehyde moiety and confirm the planar structure of each conformer. The geometries of three conformers are given as obtained from the 6-31G MO basis and may be useful to molecular spectroscopists. Theoretical and experimental dipole moments are interpolated to yield estimates of their magnitudes for the four planar conformers. Somewhat less precise 1H nmr spectral parameters (than for the above solutions) are also obtained for dilute solutions in benzene-d6 at 300 K. The conformational distributions based on these parameters are compared with their only other measurement, based on dipolar moments in benzene at 298 K. Good agreement between the results of the two methods is found for 3CNB but not for 2CNB. It is suggested that specific interactions occur between benzene solvent and solute molecules, particularly for 3CNB, for which these interactions stabilize the conformer having a low dipole moment. Remarkable changes in the intraring proton–proton coupling constants occur in going from CS2/C6D12 to acetone-d6 solution. Key words: 2- and 3-cyanobenzaldehyde (2CNB and 3CNB): 1H NMR, conformations, long-range spin–spin coupling constants, MO computations.

The sign of the long-range spin–spin coupling constant between 19F and the aldehydic 1H in p-fluorobenzaldehyde: evidence for a negative QCCHO

1969 ◽  
Vol 47 (22) ◽  
pp. 4289-4291 ◽  
Author(s):  
T. Schaefer ◽  
S. S. Danyluk
Keyword(s):  
Hyperfine Interaction ◽  
Long Range ◽  
Interaction Constant ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Spin Coupling

The spin–spin coupling constant of −0.50 ± 0.03 Hz between the 19F nucleus and the aldehydic proton in p-fluorobenzaldehyde contrasts with a positive coupling between 19F and methyl protons in p-fluorotoluene derivatives. If the former coupling is dominated by a π electron mechanism, it implies a negative hyperfine interaction constant between the aldehydic proton and the aromatic π system.

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