Spectroscopic studies of arenediazonium ion stability in surfactant solutions

Abstract

In the article a comparative study of dediazoniation of benzenediazonium, p-bromo- and p-methylbenzenediazonium ions in surfactant solutions is presented. The emphasis is put on the effects of temperature and surfactant type on decomposition. To monitor the kinetics of dediazoniation UV–VIS spectroscopy was employed. The observed rate constants, kobs, were obtained by fitting the absorbance–time data to the integrated first-order kinetic equation and then the activation energies were obtained from the Arrhenius plot. It was found that temperature is the main factor determining the decomposition rate of arenediazonium ions in aqueous acidic solutions (pH=1.81). The presence of –Br and –CH3 groups in the benzene ring makes the ions more stable in comparison with the parent ion, increasing dramatically their half-life times. The effect of surfactant on the dediazoniation was rather small, indicating that in the investigated surfactant concentration range, the effects of surfactant aggregates (single molecules, premicelles and micelles) on the dediazoniation rate constant are small.