The substituent effect on ring proton coupling constants in 3-substituted pyridines

Abstract
The proton spectra of the irradiated C and D nucleus of several 3-substituted pyridines (X = CN, OCH, Br, Cl) are recorded while detecting the signals of protons A and B with the Ipdor technique [15]. The coupling constants between the C and D protons are obtained in spite of partial overlapping and quadrupolar broadening of the signals. The results are: J CD about -0·25 c.p.s. The dependence of all the ring coupling constants on the electronegativity of X is discussed.