Magnetic Resonance Study of the Dissociation of Peroxydisulfuryl Difluoride into Fluorosulfate Radicals

Abstract

Broadening of the NMR line of 19F in peroxydisulfuryl difluoride, S2O6F2, was investigated between 40 and 100°C. The linewidth contribution from fluorine “exchanging” between the diamagnetic peroxide and paramagnetic SO3F radicals was separated from other linewidth contributions by simultaneously observing stable, inert pyrosulfuryl fluoride, S2O5F2. The concentration of fluorosulfate radicals as a function of temperature was obtained from EPR measurement by comparison of spectral intensity with that of a sample containing a known number of spins. The NMR chemical shift ΔωR of the SO3F radical was estimated from the isotropic hyperfine splitting constant A = 9.2 G, which was determined by EPR from the peroxide at liquid-nitrogen temperature under uv irradiation. The activation energy Ea = 25.0 kcal/mole for the reversible, thermally controlled reaction S2O6F2⇆2SO3F was found from the temperature variation in width of the single fluorine NMR line observed. Equations developed by Swift and Connick and Luz and Meiboom were employed.

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

“…The question arises whether cleavage of the 0-0 bond resulting in the formation of radicals like S03F'(solV) and their subsequent recombination may occur differently in HS03F solution. The NMR spectra provide no indication for the presence of radicals in concentrations large enough to effect peak positions, in respect to previous reports (37), or to cause line broadening, which has been observed in liquid S2O6F2 at elevated temperature (38). The possibility of finding radicals in HS03F solution at lower concentrations is therefore better probed by ESR.…”

“…The radical observed in solution is clearly not identical with S03Fq as reported previously (14,(38)(39)(40) or observed by us in liquid S2O6F2. Consistent with the observation of three g-values (see Fig.…”

“…The reversible dissociation of bis(fluorosulfuryl)peroxide into radicals according to: has been studied previously by ESR with the radical S03Fa observed in the liquid (14), gaseous (39), and solid phase (38,40). In addition, the radical has been generated by photolysis of fluorine fluorosulfate, FOS02F and studied in a solid CFC13 matrix at 77 K (40).…”