Proton magnetic resonance spectra of 3-fluorotoluene and 2-chloro-5-fluorotoluene. The sign and coupling mechanism of

1978 ◽  
Vol 56 (17) ◽  
pp. 2233-2236 ◽  
Author(s):  
Ted Schaefer ◽  
Werner Danchura ◽  
Walter Niemczura
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Coupling Constant ◽  
Electron Component ◽  
Electron Contribution ◽  
Full Analysis ◽  
Spin Spin Coupling ◽  
Magnetic Resonance Spectra

A full analysis of the proton magnetic resonance spectra of 3-fluorotoluene and of 2-chloro-5-fluorotoluene, as 10 mol% solutions in CS2, demonstrates that the long-range spin–spin coupling constant over five bonds between methyl protons and fluorine-19 is negative. The coupling mechanism consists of a large positive σ electron component and a negative π electron component. The negative sign of the π electron contribution arises from a spin density in the 2pz orbital at carbon-3, which is opposite in sign to that of the spin densities at C-2 and C-4. Combined with positive hyperfine interaction constants, QCCH and QCF, the consequence is a negative π electron component.

Proton magnetic resonance spectra of some benzo[b]thiophens. An investigation of substituent effects in a heteroaromatic system

1968 ◽  
Vol 21 (7) ◽  
pp. 1853 ◽  
Author(s):  
B Caddy ◽  
M Martin-Smith ◽  
RK Norris ◽  
ST Reid ◽  
S Sternhell
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Spin Coupling ◽  
Heteroaromatic System ◽  
Spin Spin Coupling ◽  
Magnetic Resonance Spectra

N.m.r. data for 19 5-substituted and 13 polysubstituted benzo[b]thiophens are tabulated. The influence of the substituents at C5 on the chemical shifts of H4 and H6 is discussed. Long-range interproton spin-spin coupling between H3 and H7, and between H2 and H6, is general in benzo[b]thiophens. The vicinal coupling J6,7 in 5-substituted benzo[b]thiophens varies directly and linearly with the electronegativity of the substituents at C5.

Fluorine magnetic resonance studies. I. para-Substituted β,β-difluorostyrenes

1972 ◽  
Vol 25 (7) ◽  
pp. 1465 ◽  
Author(s):  
ID Rae ◽  
LK Smith
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Lower Field ◽  
Magnetic Resonance Studies ◽  
Fluorine Compounds ◽  
Spin Spin Coupling ◽  
Magnetic Resonance Spectra

A series of seven para-substituted β,β-difluorostyrenes has been prepared and their proton and fluorine magnetic resonance spectra recorded. The fluorine spectra show interesting correlations with the σ- values for the para substituents, the fluorine resonances moving to lower field and the geminal fluorine-fluorine coupling constant decreasing as σ- increases. These trends parallel those observed in the analogous styrenes but rather more precise relationships have been established for the fluorine compounds. Long range fluorine-fluorine spin-spin coupling over six and seven bonds, respectively, has been observed in the β,β,β,3- and β,β,4-trifluoro-styrenes.

Nuclear magnetic resonance spectra of some aryl derivatives of mercury

1971 ◽  
Vol 24 (2) ◽  
pp. 317 ◽  
Author(s):  
PJ Banney ◽  
PR Wells
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Proton Spin ◽  
Spin Coupling ◽  
Methyl Groups ◽  
Conformational Effects ◽  
Nuclear Magnetic Resonance Spectra ◽  
Spin Spin Coupling ◽  
Derivatives Of ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of a series of arylmercury chlorides containing methyl groups or a single polar substituent have been determined paying particular attention to mercury-proton spin-spin coupling. This is readily observed for protons or methyl groups ortho or meta to mercury but rarely for the para derivatives. The ortho coupling is relatively insensitive to structure whereas the meta coupling shows considerable variations that appear to be associated with conformational effects.

Proton magnetic resonance and Raman spectroscopic studies of methylmercury (II) complexes of inorganic anions

1976 ◽  
Vol 54 (16) ◽  
pp. 2517-2525 ◽  
Author(s):  
Dallas L. Rabenstein ◽  
M. Coreen Tourangeau ◽  
Christopher A. Evans
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Proton Magnetic Resonance ◽  
Formation Constants ◽  
Spin Coupling ◽  
Donor Atom ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Raman Spectral Data ◽  
Spin Spin Coupling

Complexation of methylmercury(II) by sulfate, selenate, carbonate, sulfite, selenite, thiocyanate, selenocyanate, sulfide, and selenide in aqueous solution has been studied by proton magnetic resonance and Raman spectroscopy. Formation constants were determined for the SO42−, SeO42−, CO32−, SO32−, SeO32−, SeO3H−, SCN−, and SeCN− complexes from the pH dependence of the chemical shift and the 199Hg−1H spin–spin coupling constant of the methyl group of CH3Hg(II) in solutions containing both CH3Hg(II) and ligand. The chemical shift and the 199Hg–1H spin–spin coupling constant of the CH3Hg(II) in each of the complexes were also obtained from the same measurements. Proton magnetic resonance parameters were measured for several complexes with sulfide and selenide. The ligand donor atom in each of the complexes was identified using the formation constants, the 199Hg–1H spin–spin coupling constant of the complexed methylmercury and the Raman spectral data. It is of particular interest that, in the selenite complex, the methylmercury is bonded to an oxygen atom whereas sulfur is the donor atom in the sulfite complex.

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.

A proton magnetic resonance determination of the small rotational barriers about the C—Si bond in phenyl derivatives of chloro and methyl silanes

1977 ◽  
Vol 55 (3) ◽  
pp. 557-561 ◽  
Author(s):  
William J. E. Parr ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of ◽  
Low Energy Conformations

The long-range spin–spin coupling constants between protons bonded to silicon and ring protons in C6H5SiH3, C6H5SiH2Cl, C6H5SiH2CH3, C6H5SiHCl2, and C6H5SiH(CH3)2 are determined from the proton magnetic resonance spectra of benzene solutions. A hindered rotor treatment of the barrier to internal rotation about the C—Si bond, in conjunction with the coupling constants over six bonds, allows the deduction of the low-energy conformations for C6H5SiH(CH3)2 and for C6H5SiHCl2, as well as of barriers of 1.0 ± 0.2 kcal/mol. The approach becomes less reliable for C6H5SiH2CH3 and for C6H5SiH2Cl and, particularly for the latter compound, the derived barrier is very likely an upper limit only. Ab initio molecular orbital calculations of the conformational energies are reported for C6H5SiH3, C6H5SiH2Cl, and for C6H5SiHCl2.

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