The enthalpy of formation of thiazyl monofluoride (NSF). Bond dissociation enthalpies of thiazyl tri- and monofluorides and related nitrogen—sulfur—fluorine compounds

Thiazyl monofluoride (NSF) reacts spontaneously with excess fluorine to form SF 0 and N 2 . Calorimetric measurements of the energy of this reaction have been performed whence the standard enthalpy of formation, Δ H o f (NSF, g, 298.15 K), was found to be −(5.0 ± 0.9) kcal th mol −1 . This result is substantially more negative than that previously deduced from calorimetric and mass-spectrometric studies on NSF 3 . The enthalpy of formation calculated from the mass-spectrometric appearance potentials was based on the assumption that molecular fluorine was produced in the electron-impact process. If it is assumed instead that the fluorine was atomic , the calorimetric and mass spectrometric enthalpies of formation for NSF agree much better. The N ≡ S and S-F bond dissociation enthalpies are calculated to be (126 ± 3) and (91 ± 6) kcal th mol −1 , respectively at 298.15 K. Bond dissociation enthalpies for related nitrogen-sulfur-fluorine compounds are also reported.