Syntheses of Phenylpyrazolone Derivatives. VIII

Studies on the Absorption Spectrum of Phenylpyrazolone-azomethine Derivatives

Abstract

Absorption spectra in the visible region of 39 kinds of Phenylpyrazolone-azomethine derivatives were measured in methanol and quantitative explanation of the effect of changes in the structure of pyrazolone-azomethine molecule on the visible absorptions was discussed, based on the theory of Porter and Weissberger.
Further considerations were made on the effect steric configuration of these molecules on the absorption, from van der Waals radii, bond angle, and bond distance.
The position of the x-band due to change of substituent in the 3-position in the pyrazolone ring was in the order of NH₂>RO-C₆H₄-NH>C₆H₅⋅NH>RSO₂NH or RCONH>C₆H₅, and the absorption maximum of the x-band appeared in the shortest wave length region in the case of the amino group. There was no systematic change in the position of y-bands.
When sulfonamide radical is further introduced into the phenyl group in the 1-position of the pyrazolone ring, the x-band shifts very slightly to a longer wave length side. It was assumed that steric configurations like those indicated in (VIa), (VIIa), (VIIIa), and (IXa) seemed to be the closest to the actual state of the molecule.