Collect. Czech. Chem. Commun. 1987, 52, 727-735

13C and 15N NMR spectra of 3-methyl-1-phenylpyrazole-4,5-dione 4-(4'-substituted phenyl)hydrazones

Antonín Lyčkaa, Tibor Liptajb and Josef Jirmana

a Research Institute of Organic Syntheses, 532 18 Pardubice-Rybitví
b Department of Physical Chemistry, Slovak Institute of Technology, 812 37 Bratislava


13C and 15N NMR spectra have been measured of eleven 3-methyl-1-phenylpyrazole-4,5-dione 4-(4'-substituted phenyl)hydrazones (I). The 13C chemical shifts of the non-substituted compound I have been assigned with the use of the 1J(13C, 13C) coupling constants obtained from the 1D-INADEQUATE spectrum. The greatest changes in chemical shifts of the compounds I connected with the substituent at 4'-position have been observed for the nitrogen atoms Nα, Nβ, N2 and carbon C(4). These substitution chemical shifts have been correlated with the substituent constants by means of the equations SCS = ρ1σ1 + ρRσR + const., where σR means one of the values σR0, σRBA, σR-, or σR+. The best correlations have been obtained for the combinations Nα - σRBA, Nβ - σR-, N2 - σR0, and C(4) - σR0. The 15N substituent chemical shifts of the nitrogen atoms Nα and Nβ of compounds I have been compared with the analogous values of 4-substituted trans-azobenzenes.