The complete analysis of the 1H NMR spectra of quinoline and two of its derivatives. sign determinations of inter‐ring coupling constants by means of the INDOR technique

The complete 1H NMR spectral analyses of quinoline and two of its derivatives (4,7‐dichloroquinoline and 8‐nitroquinoline) have been performed. All the long‐range coupling constants were determined both in magnitude and sign. In determining the signs the INDOR technique was very useful and successful, allowing the resolution of transitions as close as a few hundredths of a Hz. The signs of the inter‐ring coupling constants alternate with the number of intervening bonds, according to McConnell's rule, except the all‐trans6J couplings. A linear relationship has been found between the 1H−1H and 19F−19F inter‐ring coupling constants for which the spin polarization is transmitted almost exclusively via the π‐electron system.