Deuterium isotope effects in 13C NMR spectra of trans-N-salicylideneaniline isotopomers

A series of isotopically labelled trans-N-salicylideneaniline (SAN) isotopomers has been prepared (2'-H-2-, 3-H-2-, 4'-H-2- and 2',3',4',5',6'-H-2(5)-SAN) and their C-13 NMR spectra recorded and analyzed. Deuterium isotope effects (DIEs) in C-13 NMR spectra of SAN isotopomers have been compared with those observed in the corresponding isotopomers of related binuclear aromatic molecules. Most of DIEs in SAN resemble those previously reported for similar molecular systems, except for some effects over three bonds. It is suggested that the participation of SAN nitrogen lone pair in the intramolecular hydrogen bond is responsible for the observed difference in DIEs through three bonds at the aniline ring ortho carbon.