Oldřich Machalický

Structure and properties of fluorescent reactive dyes : Electronic structure and spectra of some benzanthrone derivatives

Absorption and fluorescence spectra of N-(disubstituted-1,3,5-triazinyl)-3-aminobenzanthrones, 3-acetylaminobenzanthrone and 3-methoxybenzanthrone have been investigated. Excitation energies and the character of the first absorption band have been calculated by the PPP-MO method. Some data on substituent and solvent effects on fluorescence spectral position and quantum yields are reported. The connection between electron density distribution in the electronic ground and excited state, and spectroscopic properties of those compounds, is explained.

Voltammetric Determination of Nitro Derivative of Synthetic Antioxidant 2,6-di-tert-butyl-4-methyl-phenol

ABSTRACT A new method is reported for the determination of the nitro derivative of the synthetic antioxidant 2,6-di-tert-butyl-4-methyl-phenol by differential pulse voltammetry with a hanging drop mercury electrode. Standard 2,6-di-tert-butyl-4-methyl-4-nitro-2,5-cyclohexadiene-1-one was synthesized for voltammetric determination after nitration. A nitration mechanism in acetic anhydride was proposed. The analyte provided a voltammetric signal in a mixture of 0.014 mole per liter potassium chloride and 94% ethanol. The developed method was employed for the determination of 2,6-di-tert-butyl-4-methyl-phenol in oil with satisfactory results, suggesting future application for practical analysis.

Acidobasic equilibria and spectral characteristics of acetyl and tosyl derivatives of 4,4'-diaminostilbene-2,2'-disulfonic acid

Abstract Acetyl and tosyl derivatives of 4,4′-diaminostilbene-2,2′-disulfonic acid and their N , N ′-dimethyl analogues were prepared. The course of syntheses was checked by HPLC and products were identified with NMR spectroscopy. Chemical stability was tested in phosphate buffers. Acidobasic properties of prepared substances were studied with potentiometric titration and also with absorption and fluorescence spectrophotometry. The fluorescence quantum yields of pure acidobasic forms were measured. The tosylamino derivative was found to behave as N-acid and in aqueous alkali medium exhibits a strong fluorescence. The p K A values were estimated.