The system fluorosulfuric acid (HSO3F) and bis(fluorosulfuryl)peroxide (S2O6F2) — a solution study

Abstract

Solutions of bis(fluorosulfuryl)peroxides, S2O6F2, in fluorosulfuric acid, HSO3F, are synthetically very useful. The nature of the solvent (HSO3F)–solute (S2O6F2 or SO3F•) interaction is probed by Raman, 1H and 19F NMR, and ESR spectroscopy, the latter focussing on the radical SO3F• formed by the dissociation of S2O6F2. Both S2O6F2 and SO3F• behave as very weak bases in HSO3F. Proton transfer between solvent and solute and SO3F exchanges are suggested on the basis of NMR and ESR measurements. The symmetry and electronic structure of the SO3F• radical are altered in HSO3F solution. A giso value of 1.97267 is obtained. The radical appears to be formed on dissolution of S2O6F2 at room temperature and persists down to 183 K. The solvent–solute interaction depends on the acid strength of the protonic solvent and addition of the base KSO3F to HSO3F leads to a loss of solubility and the separation of S2O6F2 as a second phase. Keywords: solution study in HSO3F of weak bases, Raman spectrum, ESR study in HSO3F.