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Updated: Jun 28, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Basicity of nitropyrazoles and their simultaneous spectrophotometric determination
1Research Laboratory "Galenika", Zemun, Yugoslavia.
Abstract:
The protonation constants of some 1-, 3(5)-, 3-, 4- and 5-nitropyrazoles have been determined, and compared with those of nitroimidazoles. The effect of the position of the nitro group in the pyrazole and imidazole ring is discussed. The ortho effects of the nitro group in pyrazole and imidazole are compared and found to have identical values. The effect of the nitro group on protonation constants is greater when the nitro group is close to the pyridine nitrogen atom. This, together with the ability of N-unsubstituted nitropyrazoles to dissociate to give nitropyrazole anions, with an accompanying shift of the spectra to longer wavelengths, permits the simultaneous spectrophotometric determination of nitropyrazoles.
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