Spin–spin coupling between proximate protons on neighbouring aromatic rings and between hydroxyl protons in 2,2′-dihydroxy-4-methoxybenzophenone. Coupling through the hydrogen bond

1976 ◽  
Vol 54 (14) ◽  
pp. 2231-2234 ◽  
Author(s):  
Ted Schaefer ◽  
Kalvin Chum
Keyword(s):  
Hydrogen Bond ◽  
Relative Orientation ◽  
Spin Coupling ◽  
Weak Hydrogen Bond ◽  
Aromatic Rings ◽  
Covalent Character ◽  
Nonbonded Interactions ◽  
Direct Mechanism ◽  
Hydroxyl Protons ◽  
Spin Spin Coupling

The doubly hydrogen bonded conformation of 2,2′-dihydroxy-4-methoxybenzophenone ensures substantial nonbonded interactions between C—H bonds on neighbouring aromatic rings and gives rise to spin–spin coupling between the protons in those bonds. Because of the relative orientation of the C—H bonds containing the coupled protons, the coupling represents a direct mechanism which probably does not depend on the orbitals of the carbon atom. The observed coupling between the hydroxyl protons, formally over eight bonds, is small and indicative of an inappreciable covalent character of the hydrogen bond, in agreement with recent conclusions that a weak hydrogen bond is best represented by electrostatic and non-bonded forces only.

Stereospecific Spin–Spin Coupling between Hydroxyl Protons and 19F Nuclei in o-, m- and p-Fluorophenol Derivatives. "Through-space" Interactions via the Hydrogen Bond

1975 ◽  
Vol 53 (7) ◽  
pp. 986-992 ◽  
Author(s):  
J. Brian Rowbotham ◽  
Murray Smith ◽  
Ted Schaefer
Keyword(s):  
Hydrogen Bond ◽  
Substituent Effects ◽  
Proton Exchange ◽  
Spin Coupling ◽  
Side Chain ◽  
Molecular Orbital Calculations ◽  
Coupling Mechanism ◽  
Fluorine Nucleus ◽  
Hydroxyl Protons ◽  
Spin Spin Coupling

Under conditions of slow intermolecular hydroxyl proton exchange 6JpOH,F < 0, 5JtransOH,F > 0, 5JcisOH,F < 0, 4JoOH,F < 0 in fluorophenol derivatives. 5JmOH,F is remarkably insensitive to intrinsic substituent effects, yields accurate values of conformational populations of m-fluorophenol derivatives and can be used to demonstrate a buttressing effect on the strength of the relatively weak [Formula: see text] hydrogen bond. 4JoOH,F displays a stereospecific dependence opposite to that of other couplings from a side-chain proton to a ring fluorine nucleus, is apparently very sensitive to the distance between proton and fluorine nucleus and is cited as an example of a negative through-space coupling mechanism. Approximate molecular orbital calculations give some support to the last suggestion.

Nuclear spin-spin coupling via nonbonded interactions. 7. Effects of molecular structure on nitrogen-fluorine coupling

1992 ◽  
Vol 57 (1) ◽  
pp. 366-370 ◽  
Author(s):  
Frank B. Mallory ◽  
Eddie D. Luzik ◽  
Clelia W. Mallory ◽  
Patrick J. Carroll
Keyword(s):  
Molecular Structure ◽  
Nuclear Spin ◽  
Spin Coupling ◽  
Nonbonded Interactions ◽  
Spin Spin Coupling

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

Sign in / Sign up

Export Citation Format

Share Document