Browsing by Author "Szyper, Mira"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Polarography and Solvatochromism: Part 2.—Comparison of Electrochemical and Spectral Properties of 5'-Methoxy-2'-hydroxy-Ar-methyl-4-stilbazolium Iodide
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (07), 1977) Szyper, Mira; Zuman, Petr
    When polarographic half-wave potentials of 5′-methoxy-2′-hydroxy-N-methyl-4-stilbazolium iodide were measured at pH > 13 in mixtures of water with DMF and DMSO, practically no solvent effect was observed. In this pH-range the betaine form of the stilbazole derivative is reduced. Spectra of the betaine form (II) in the solvent mixtures have shown shifts of electronic absorption bands of up to 100 nm. Either changes in the solvent–solute interaction in the excited state or different solvent–solute interactions in the bulk of the solution and at the electrode surface, where the solute is oriented or adsorbed, are considered to explain this difference. Changes in spectra and heights of polarographic waves and shifts of half-wave potentials indicate interaction of the phenolic form (I) of the stilbazole derivative with a form of boric acid.
  • No Thumbnail Available
    Item
    Polarography and Solvatochromism: Part 1.—Polarographic Reduction of 5'-Methoxy-2'-hydroxy-N-methyl-4-stilbazolium Iodide and Related Compounds
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (07), 1977) Zuman, Petr; Szyper, Mira
    2’-Hydroxy-N-methy]-4-stilbazolium iodide (IIa), its 5'-chloro-(lIc) and 5'-nitro-(IIb) derivatives arc strongly adsorbed at the surface of the dropping mercury electrode (d.m.e.). 5'-Methoxy-2- hydroxy-lV-methyl'4-stilbazoliuin (Ild) iodide proved to be less strongly adsorbed and is reduced in the protonated form at lower pH-values in two one-electron steps. The product of reduction in the first step can undergo protonation, and protonated and unprotonated radicals undergo reduction at different potentials. When the properties of the betaine form of compound (lId) are to be studied, the half-wave potentials must be measured at pH 13-14, as at lower pH-values reduction of the phenolic form predominates.