Isothiosemicarbazones, except N2-substituted ones, were found to exist exclusively in the amino structure by means of ir and nmr spectroscopy. The cis configuration (N1 cis to N4 about the N2= C bond) with intramolecular hydrogen bonding was proposed as the predominant structure for N4-unsubstituted isothiosemicarbazones on the basis of the ir spectra from the partially deuterated compounds. The trans configuration (N1 trans to N4 ...
