The sign of the 'through-space' spin–spin coupling between methyl protons and the fluorine nucleus in 2,6-dimethylbenzoyl fluoride

1976 ◽  
Vol 54 (5) ◽  
pp. 800-804 ◽  
Author(s):  
Ted Schaefer ◽  
Kalvin Chum ◽  
Kirk Marat ◽  
Roderick E. Wasylishen
Keyword(s):  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Fluorine Nucleus ◽  
Methyl Group ◽  
Out Of Plane ◽  
Spin Spin Coupling ◽  
Coupling Mechanisms ◽  
Carbonyl Fluoride

The spin–spin coupling constant over five formal bonds between 19F and methyl protons, [Formula: see text], in 2,6-dimethylbenzoyl fluoride is −3.1 Hz. Observation of a nonzero [Formula: see text] indicates an out-of-plane conformation for the carbonyl fluoride group and implies substantial nonbonded repulsions between the methyl and carbonyl fluoride groups. It is argued that [Formula: see text] is as small as −7 Hz when the C—F bond lies cis to a methyl group and that its magnitude is a consequence of the so-called 'through-space' coupling mechanisms. On the basis of INDO–MO–FPT computations, it is suggested that such observed couplings are a composite of large contributions of either sign and, therefore, that observed through-space 1H,19F couplings may be of either sign if conformational averaging occurs.

The range of in anisole derivatives. An indicator of torsion and compression of the methoxy group

1985 ◽  
Vol 63 (3) ◽  
pp. 782-786 ◽  
Author(s):  
Ted Schaefer ◽  
Salman R. Salman ◽  
Timothy A. Wildman ◽  
Glenn H. Penner
Keyword(s):  
Methoxy Group ◽  
Bond Angle ◽  
Average Distance ◽  
Electron Donors ◽  
Spin Coupling ◽  
Ortho Position ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Methyl Group ◽  
Spin Spin Coupling

In a series of anisole derivatives, [Formula: see text], the spin–spin coupling constant between the methyl protons and the ring proton in the ortho position, ranges from −0.23 to −0.38 Hz when the methyl group lies cis to the ortho C—H bond. 5J, as a proximate coupling, is sensitive to the average distance between the coupled protons. Its variation with substituent can be rationalized in terms of torsion about the Csp2—O bond and changes in the bond angles near the methoxy moiety. The theoretical 5J numbers can be empirically reproduced by a cos4 ψ function, where ψ is the angle by which the methoxy group twists out of the benzene plane. In general, large ortho substituents cause an increase in the magnitude of 5J (bond angle changes), strong π electron donors in the para position cause a decrease in the magnitude of 5J (increased torsional freedom), and π electron acceptors do the opposite (decreased torsions).

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.

Form of the dihedral angle dependence of the spin-spin coupling constant JHNNH

1989 ◽  
Vol 25 (3) ◽  
pp. 338-341
Author(s):  
L. M. Kapkan ◽  
A. Yu. Chervinskii ◽  
T. M. Pekhtereva ◽  
Yu. I. Smirnov ◽  
A. F. Dmitruk
Keyword(s):  
Dihedral Angle ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Angle Dependence ◽  
Spin Spin Coupling

The proximate spin–spin coupling, 5J(F,CH3), as a quantitative conformational indicator in alkylfluorobenzenes and related compounds

1986 ◽  
Vol 64 (8) ◽  
pp. 1602-1606 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Glenn H. Penner ◽  
S. R. Salman
Keyword(s):  
Nuclear Spin ◽  
Spin Coupling ◽  
Torsional Angle ◽  
Rotational Behaviour ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Spin Coupling ◽  
Torsional Potentials ◽  
Derivatives Of ◽  
Related Compounds

The through-space or proximate nuclear spin–spin coupling constant, 5J(F,CH3) = 5J, between methyl protons and ring fluorine nuclei in alkylfluorobenzenes is postulated as [Formula: see text] θ being the torsional angle for the [Formula: see text] bond. A and B are obtained from the known internal rotational behaviour in 2,6-difluoroethylbenzene and the corresponding cumene derivative. The parameterization is tested on the observed 5J in derivatives of 2,4,6-tri-tert-butyl- and 2,4,6-tri-isopropyl-fluorobenzene, in 2-chloro-6-fluoroisopropylbenzene, 2,6-difluoro-α-methylstyrene, and N-methyl-8-fluoroquinolinium halides. A prediction is made for 5J in 2,6-difluoro-tert-butylbenzene. It appears that the present parameterization allows the derivation of approximate torsional potentials from proximate couplings, for example in α,α-dimethyl-2,6-difluorobenzyl alcohol.

Nuclear spin-spin coupling constant of hydrogen molecule with deuterium (HD)

1988 ◽  
Vol 92 (11) ◽  
pp. 3056-3059 ◽  
Author(s):  
Jens Oddershede ◽  
Jan Geertsen ◽  
Gustavo E. Scuseria
Keyword(s):  
Nuclear Spin ◽  
Hydrogen Molecule ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Spin Coupling
Sign in / Sign up

Export Citation Format

Share Document