Signs of methyl–methyl proton spin–spin coupling constants in xylene derivatives (interbenzylic coupling)

1970 ◽  
Vol 48 (6) ◽  
pp. 1002-1007 ◽  
Author(s):  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Double Resonance ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Methyl Proton ◽  
Π Interactions ◽  
Methyl Methyl ◽  
Para Xylene ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The signs of the intermethyl proton spin–spin coupling constants in ortho, meta, and para xylene derivatives (interbenzylic coupling) have been determined by double resonance techniques. [Formula: see text] [Formula: see text] and [Formula: see text] are positive, negative, and positive, respectively, in agreement with the predictions of theories based on σ–π interactions. The magnitudes of the coupling constants are discussed in terms of the values predicted by these theories.

Methyl–Methyl Proton Spin–Spin Coupling Constants in Some Six-membered Ring Compounds. A Test for Delocalization in Borazine

1974 ◽  
Vol 52 (3) ◽  
pp. 489-496 ◽  
Author(s):  
J. Brian Rowbotham ◽  
T. Schaefer
Keyword(s):  
Electron System ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Substitution Pattern ◽  
Methyl Proton ◽  
Ring Compounds ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

Spin–spin coupling constants over five, six, and seven bonds between protons in different methyl groups are reported for the xylenes, derivatives of benzene, pyridine, pyrimidine, pyridinium salts, p-benzoquinone, and borazine. The coupling magnitudes are characteristic of the substitution pattern in the delocalized systems. Calculations at the INDO-MO-FPT level of methyl proton couplings in N- and B-methylborazines are in agreement with the available experimental evidence in indicating a relatively weak transmission of spin density information via the presumed π electron system of borazine.

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.

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