Investigation of the configuration of alkyl phenyl ketone phenylhydrazones from ab initio ¹H NMR chemical shifts

Using ab initio GIAO calculations the experimental H NMR spectra of the E and Z isomers of alkyl phenyl ketone phenylhydrazones R1-C(Ph)=N-NH-Ph (R1 = Me, Et, iPr, and tBu) have been re-interpreted and deviations from Karabatsos' rule or from the assignment of Bellamy and Hunter have been discussed in the light of the optimized geometrical structures.