Ferricyanide-catalyzed amination of phenol: a near-infrared spectroscopic and kinetic study

摘要

Abstract This study applied a UV–Visible-NIR double-beam spectrometer to characterize the formation of an infrared-active organic dye product that results from the dehydration amination reaction that occurs between phenol and 4-aminoantipyrine. Time-dependent wavelength scan absorption measurements in the presence of ferricyanide ions exhibited spectral evidence of the formation of the phenolic dye product, which is characterized by the appearance of a broad absorption band in the near IR spectral region with a λ max. ≈documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$approx $$end{document} 1050?nm (or ≈documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$approx $$end{document} 9524?cm?1). Similar reaction monitoring experiments in the absence of the ferricyanide ions showed no appreciable formation of the phenolic dye product, which characterized the catalytic action of the ferricyanide? ion. The kinetic experiments and fitted tests revealed that the reaction proceeds via first?order kinetics (R2?=?0.99) with an average rate constant of 0.0026?s?1 and a half-life of 266?s within the first 1000?s. A positive correlation between catalyst concentration and the average catalytic rate constant was established. The concentration-dependent NIR wavelength spectral scan measurements characterized the spectrophotometric quantitation application of the formation of phenolic dye-related compounds that showed a remarkable linear response to the analyte concentration within the ppb range of between 25 and 100?μg/dm3.Graphical abstract