Proton Magnetic Resonance Spectra of 2‐Pyridines. The Strong‐CoupledAA′KLSystem

Abstract

The 60‐Mc/sec spectra of 2‐chloro, 2‐cyano, 2‐bromo, and 2‐acetyl pyridines are studied and analyzed as ABKL and AA′KL systems. The results are compared with the exact ABCD solution given by a computer. It is shown that if one of the coupling constants is greater than the corresponding chemical shift, the AA′KL approximation can give a good account of the frequencies of the lines of the experimental spectrum, but not so good for the intensities. The molecular parameters calculated with both approximate methods differ only some hundredths of a cycle per second from the values given by the computer. An iterative method based on the use of average group frequencies and average splittings and improved by the use of the principle of least squares is fully described.