Dissociation and rate of proton transfer of HXO3 (X = Cl, Br) in aqueous solution determined by Raman spectroscopy

Raman spectra of aqueous halate and oxyacids HXO3 (X = Cl,Br) solutions were obtained. Integrated Raman intensity measurements of the 804 and 933 cm(-1) bands of HBrO3 and HClO3 in aqueous solutions, respectively, allowed the determination of the degree of dissociation of these acids in the molarity range studied. The results show that these acids are almost completely dissociated until the maximum concentration studied. In addition, we observed that bromic and chloric acid solutions with concentrations greater than or equal to3.2 and 2.5 mol L-1, respectively, decompose to bromine and chlorine at room temperature. The trend of the Raman specific intensities of the halate ions (BrO3- > ClO3-) bands in aqueous solutions is discussed and compared with that observed by other workers who considered the contributions of the isotropic and anisotropic components of the polarizability tensor. Measurements of the Raman line broadening of the same bands gave values of 2.6 X 10(11) L mol(-1) s(-1) for the second-order rate constant of the reaction between H+ and BrO3- and 3.4 x 10(11) L mol(-1) s(-1) for the reaction between H+ and CIO3. Copyright (C) 2001 John Wiley Sons, Ltd.