Proton Magnetic Resonance Study of Intramolecular Hydrogen Bonding in Halophenols

1974 ◽  
Vol 52 (17) ◽  
pp. 3037-3041 ◽  
Author(s):  
J. Brian Rowbotham ◽  
T. Schaefer
Keyword(s):  
Intramolecular Hydrogen Bonding ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Magnetic Resonance Study ◽  
Hydroxyl Proton ◽  
Hydrogen Bond Strength ◽  
Proton Magnetic Resonance Study ◽  
Spin Coupling Constants ◽  
Intramolecular Hydrogen ◽  
Spin Spin Coupling

The long-range spin–spin coupling constants over five bonds between the hydroxyl proton and the ring protons in a series of trihalophenols imply that the intramolecular hydrogen bond strength (negative enthalpy) to fluorine is greater than that to iodine by 75 ± 20 cal/mol, whereas the strengths to chlorine and bromine are 460 ± 60 cal/mol greater than to iodine. If a distinction can be made between chlorine and bromine, then chlorine–hydrogen bonds more strongly by only a few tens of calories per mol. The measurements were made mainly on dilute solutions in carbon tetrachloride at 32 °C.

scholarly journals Proton Magnetic Resonance Spectra, Conformational Preferences, and Approximate Molecular Orbital Calculations for the syn and anti 2-Furanaldoximes

1972 ◽  
Vol 50 (2) ◽  
pp. 274-280 ◽  
Author(s):  
R. Wasylishen ◽  
T. Schaefer
Keyword(s):  
Molecular Orbital ◽  
Dipole Moments ◽  
Intramolecular Hydrogen Bonding ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Conformational Preferences ◽  
Spin Coupling Constants ◽  
Intramolecular Hydrogen ◽  
Spin Spin Coupling

Evidence is adduced, mainly from proton chemical shift and long-range coupling constant data, that the anti isomer of 2-furanaldoxime exists almost exclusively in the s-cis form in solution, independently of the type of intermolecular association that occurs. Intramolecular hydrogen bonding apparently is absent in this isomer. Similarly, the syn isomer exists in roughly equal mixtures of s-cis and s-trans forms in solvents of widely different polarities. A variety of nuclear spin–spin coupling constants are calculated via the INDO and CNDO molecular orbital approximations, as are the dipole moments and conformational energies, for 2-furanaldehyde and its oximes. On the whole the experimental trends are well reproduced by the computations.

Information from stereospecific spin–spin couplings about the relative absorptivities of the hydroxyl stretching bands in 2-iodophenol solutions

1981 ◽  
Vol 59 (21) ◽  
pp. 3021-3025 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Timothy A. Wildman
Keyword(s):  
Free Energy ◽  
Molecular Orbital ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Temperature Dependent ◽  
Hydroxyl Proton ◽  
Spin Coupling Constants ◽  
Cis And Trans ◽  
Spin Spin Coupling

The stereospecific spin–spin coupling constants between the hydroxyl proton and the ring protons for 2-iodophenol in various solvents yield some free energy differences between the cis and trans conformations of this molecule at 305 K. Comparison with areas of the hydroxyl stretching bands in the same or similar solvents shows that the ratio of the absorptivity coefficients for the two conformers is sensitive to solvent. It is suggested that this ratio is temperature dependent and therefore apparent enthalpy differences must be considered tentative for at least some solutions. Molecular orbital calculations are consistent with the arguments concerning the absorptivity coefficients.

Proton Magnetic Resonance Study of Conformational Equilibria of the Pyridinealdehydes in Solution. Comparison with Other Methods

1974 ◽  
Vol 52 (23) ◽  
pp. 3986-3995 ◽  
Author(s):  
Werner Danchura ◽  
Ted Schaefer ◽  
J. Brian Rowbotham ◽  
Donald J. Wood
Keyword(s):  
Coupling Constants ◽  
Spin Coupling ◽  
Trans Form ◽  
Nonpolar Solvents ◽  
Conformational Equilibria ◽  
Proton Magnetic Resonance Study ◽  
Precise Measure ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Solvation Theory

A p.m.r. study of the pyridinealdehydes shows that accurate spectral analysis yields long-range spin–spin coupling constants which are a precise measure of the conformational equilibria in solution. Thus, in CS2 solution the ON-trans form of 2-pyridinealdehyde is more stable than the ON-cis form by at least 2.3 kcal/mol, while in acetone solution it is 1.6 kcal/mol more stable than the cis form. Classical solvation theory allows the conclusion that in the gas phase the trans form is more stable than the cis form by about 7 kcal/mol, in contradiction to the predictions of approximate MO theory at the INDO level. The trans form of 3-pyridinealdehyde is also more stable than the cis form in polar and in nonpolar solvents. The results are compared with those of other experiments on these equilibria.

Vinylsilylferrocenes and Ethynyl(vinyl)silylferrocenes. Synthesis, Multinuclear Magnetic Resonance Study and DFT Calculations

2014 ◽  
Vol 69 (6) ◽  
pp. 704-714 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Elena V. Klimkina
Keyword(s):  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Magnetic Resonance Study ◽  
Nmr Parameters ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Multinuclear Magnetic Resonance

Ferrocenylsilanes with various functions at silicon (chlorine, vinyl, ethynyl) were prepared and studied by multinuclear magnetic resonance methods (1H, 13C, 29Si NMR spectroscopy). The gasphase geometries of the silanes were optimized by calculations at the B3LYP=6-311+G(d,p) level of theory, and NMR parameters (chemical shifts δ13C, δ29Si, spin-spin coupling constants) were calculated at the same level of theory.

Concerning the nonexistence of the intramolecular hydrogen bond in 2-nitrothiophenol

1977 ◽  
Vol 55 (21) ◽  
pp. 3732-3735 ◽  
Author(s):  
Ted Schaefer ◽  
William J. E. Parr
Keyword(s):  
Hydrogen Bond ◽  
Free Energy ◽  
Intramolecular Hydrogen Bond ◽  
Energy Difference ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Free Energy Difference ◽  
Spin Coupling Constants ◽  
Intramolecular Hydrogen ◽  
Spin Spin Coupling

The long-range spin–spin coupling constants between the sulfhydryl proton and the ring protons in 2-nitrothiophenol in CDCl3 and C6D6 solutions suggest the presence of two conformers in which the S—H bond prefers the benzene plane. The conformer in which the S—H bond lies trans to the nitro group is favoured over the cis conformer by a free energy difference of 0.5 ± 0.2 kcal/mol at 305 K. Apparently any intramolecular hydrogen bond is very weak compared to that in 2-nitrophenol.

Spin–spin coupling between hydroxyl and aldehydic protons in some salicylaldehyde derivatives. Correlation with the hydroxyl proton chemical shift

1984 ◽  
Vol 62 (2) ◽  
pp. 326-331 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Reino Laatikainen ◽  
Salman R. Salman
Keyword(s):  
Chemical Shift ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Spectral Parameters ◽  
Hydroxyl Proton ◽  
H Nmr ◽  
Group A ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

1H nmr spectral parameters are reported for salicylaldehyde and 15 of its derivatives in dilute CCl4 solutions. In those compounds in which sufficiently large substituents are placed ortho to either of the functional groups or in which substituents enhance the charge density in the carbonyl group, a positive spin–spin coupling is observed between the two sidechain protons. This coupling, formally over five bonds, correlates with the chemical shift of the hydroxyl proton. The coupling mechanism is discussed from various viewpoints. STO 3G MO calculations give an optimized planar structure for salicylaldehyde. Nonplanar structures are less stable than the planar form. The energy of the hydrogen bond in salicylaldehyde lies near 30 kJ/mol and increases to 36 kJ/mol in the 4,6-dimethoxy derivative. Other small long-range spin–spin coupling constants in these compounds are also discussed.

Vibrational and thermal averaging of the indirect nuclear spin-spin coupling constants of CH4, SiH4, GeH4 and SnH4

1997 ◽  
Vol 91 (5) ◽  
pp. 897-907 ◽  
Author(s):  
SHEELA KIRPEKAR ◽  
THOMAS ENEVOLDSEN ◽  
JENS ODDERSHEDE ◽  
WILLIAM RAYNES
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling
Sign in / Sign up

Export Citation Format

Share Document