Real-time resonance Raman spectroscopic monitoring of the Briggs–Rauscher reaction

Abstract

The Briggs–Rauscher reaction is a prototypical oscillating system and is based on chemical mixtures of iodate (IO₃⁻), hydrogen peroxide, malonic acid and Mn²⁺ ions in an acidic solution. Although the Briggs–Rauscher oscillatory behaviour can be seen visibly, conventional analytical methods lack molecular detail of the exact chemical reactions within this highly dynamic system. Using real-time resonance Raman spectroscopy at 785 nm excitation, we track iodine speciation through distinct triiodide and pentaiodide signatures. Fourier-transform analysis of these time-series Raman data reveals that increasing temperature accelerates oscillation frequency while destabilising oscillatory regularity at elevated temperatures (43 °C); higher iodate concentrations promote regular oscillations at intermediate levels but suppress them through excessive oxidation at high concentrations; and starch actively modulates the reaction by stabilising polyiodide formation and doubling the oscillation period relative to starch-free conditions. This study demonstrates Raman spectroscopy as a precise physicochemical tool for analysing chemical oscillations.