1 H NMR spectra of E and Z pyridine‐2‐carbaldehyde 2′‐pyridylhydrazone and related compounds

Proton magnetic resonance spectra at 100 MHz are reported for the E ‐ and Z ‐isomers of pyridine‐2‐carbaldehyd 2′‐ pyridylhydrazone in carbon tetrachloride, d 6 ‐dimethylsulphoxide and d 6 ‐benzene solutions, and for various monomethylated derivatives in d 6 ‐dimethylsulphoxide. The spectral parameters obtained by analysis with the help of LAOCOON 3 are discussed in terms of solvent effects and the chemical shift changes consequent upon isomerisation are evaluated. Some conclusions are reached concerning the preferred conformations of the E ‐ and Z ‐isomers of pyridine‐2‐carbaldehyde 2′‐pyridylhydrazone.