Influence of Phosphate Buffer on the Reaction of 3‐Nitrophenylboronic Acid with Alizarin Red S

Abstract

AbstractThe influence of phosphate buffer on the reaction of boronic acid with 1,2‐diol was studied using a reaction system suitable for kinetics and the reaction of 3‐nitrophenylboronic acid (3‐NO2PhB(OH)2) with alizarin red S. The reaction was accelerated with increasing concentrations of phosphate buffer. 1H and 11B NMR spectra were recorded for four pH‐controlled solutions, each containing different boronic acids, to determine the cause of the reaction rate acceleration. The results indicated that HPO42− interacted with both 3‐NO2PhB(OH)2 and 3‐NO2PhB(OH)3−, whereas H2PO4− hardly interacted with either 3‐NO2PhB(OH)2 or 3‐NO2PhB(OH)3−. The reaction rates were enhanced by the formation of outer‐sphere complexes between RB(OH)2 and HPO42− and RB(OH)3− and HPO42−.