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Kreuzkonjugierte Cyanine und Merocyanine aus Salzen 1‐substituierter 2,3‐Dimethylchinoxaline. 3. Mitteilung . Über die Indikatoreigenschaften der Farbbasen und die Tautomerie der konjugaten Farbsäuren
Author(s) -
Schelz Dieter
Publication year - 1983
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19830660133
Subject(s) - chemistry , tautomer , cyanine , chlorobenzene , substituent , medicinal chemistry , base (topology) , merocyanine , polymer chemistry , organic chemistry , molecule , fluorescence , mathematical analysis , physics , mathematics , quantum mechanics , catalysis
Crossconjugated Cyanines and Merocyanines, Obtained from Salts of 1‐Substituted 2,3‐Dimethylquinoxalines: On the Properties of the Dye Bases in Acidic Media UV./VIS. and 1 H‐NMR. spectra of the indicator bases 1 in acidic solutions are presented. The solutions of the dye acids N and NN′ (Scheme 2) are in general not stable due to tautomerism. The relative p K a ‐values are set in relation to data of equilibria and half‐life periods. The latter ones depend on the substituents and on the acidity of the solutions. An inverse substituent effect observed in protic solvents is ascribed to solvolytic reactions. The dye base 1S (X = SO 3 Na, R = C 6 H 5 ) was synthesized starting with chlorobenzene. The cyanines 2 were obtained on treatment of 1 with HClO 4 in CH 3 CN; solutions of 1 in H 2 SO 4 , however, yielded on dilution tautomeric salts that were isolated as the perchlorates 3 .