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N1-acetylacetamidrazones and N1-benzoylacetamidrazones (1a–d) were characterized by 1H and 13C NMR spectroscopy. The actual tautomeric form present has been shown to be the amide hydrazone. NMR spectra of N1-acetylacetamidrazones (1a,b) showed the existence of Z and E isomers in solution, while N1-benzoylacetamidrazones (1c,d) were present as Z isomers. The crystal structures of the amidrazones have been determined at 173 and 293 K, respectively. The amidrazones 1c and 1d crystallize in the monoclinic system: in particular for 1c space group P21/c, with a = 11.016(5), b = 20.594(14), c = 13.657(7) Å; β = 98.29(3)°; V = 3066(3) Å3 and Dc = 1.243 g/cm3 for Z = 4; for 1d space group P21/a, with a = 9.410(5), b = 10.449(3), c = 14.295(11) Å; β = 101.04(5)°; V = 1380(1) Å3 and Dc = 1.220 g/cm3 for Z = 4. The X-ray diffraction analysis carried out on 1c has shown the presence of three molecules in the asymmetric unit which differ for the orientation of the phenyl ring.