Synthesis, Characterization and Analytical Study of New Azo Compounds for using Acid-base Indicators

Abstract

A diazotization method was used to synthesize new azo compounds, to which phenol was subsequently added to diazonium salt solution in the basic medium at temperatures ranging from 0 to 5 °C and compounds were characterized by FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. The potential of the compounds as acid-base indicators was tested by determining their ionization and protonation constants at different pH levels (1 to 14) using a DMSO solution of the synthesized compounds. UV-Vis spectra show a maximum wavelength (380-390 nm) observed at pH 1-7, indicating the cationic formula (a protonated form of compound H2 and H4), another peak (470-530 nm) appears at pH 8-13, indicating the ionic formula (a deprotonated form of compound H2 and H4), and compound H5 is observed at 560 nm at pH 1-7. Another peak appears at 505 nm at pH 8–13, attributable to absorption of the ionic formula (deprotonated form of compound H5). Molecules H2, H4, and H5 showed distinct colour changes when shifted to acidic and basic conditions. Furthermore, these compounds showed exceptional accuracy in drawing conclusions about the phenomenon.