A new thiazolylazo reagent 1-[(5-benzyl-1,3-thiazol-2-yl)diazenyl]naphthalene-2-ol has been synthesized via arylation of acrolein and further diazotization and diazocoupling with 2-naphthol. The chemical structure of the compound was confirmed by IR, NMR: 1 H, 13 C, COSY, HSQC and SALDI-MS spectral data. The DSC method was employed to determine the melting point and the enthalpy of fusion (T fus = 159.7°C and DH fus = 28.0 kJ mol -1 , respectively). Thermal stability and decomposition studies of the obtained azo dye were performed in air and nitrogen atmosphere using the TG technique. The evolved gases from the heated sample were registered on FTIR spectra. The decomposition of the azo dye in air atmosphere occurred in five consecutive stages. The pK a ionization constants of the substance were determined in ethanol-water mixture (1:1 v/v) by means of the spectroscopic method and were found to be equal to 0.41 for pK a1 and 9.59 for pK a2 . Using the spectrophotometric procedures, the methods for determination of trace amounts of toxic metallic ions with the new reagent were characterized and limits of detection were calculated.
The synthesis conditions of quercetin-8-sulfonic acid and sodium salt of sulfonated quercetin were determined. The molecular formulae of obtained compounds are: C 15 H 10 O 10 SÁ4H 2 O and C 15 H 9 O 10 SNaÁ4H 2 O. On the basis of spectral methods UV-Vis, IR, and 1 H NMR it was stated that the sulfonation of quercetin occurs at 8-C position of the A ring. The complexing properties of Na-QSA-8 were confirmed by synthesis of a solid complex with Fe(II) ions. The NaQSA-8 formed a complex with Fe(II) ions at pH 5 with the metal excess (c M :c L = 7:1). The chelation site was analyzed using spectroscopy methods. It was found that chelation of the metal ions occurs at the 4C=O, 3-OH and 3 0 -OH, and 4 0 -OH sites of the molecule NaQSA-8. Thermal decomposition of the compounds was carried out in air and nitrogen gas carries. The TG-FTIR-MS technique was employed to study decomposition pathway. The dehydration process was discussed in relation to of the nature of water contained in the compounds.
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