Thermochemistry of Gas-Phase Thermal Oxidation of C₂ to C₈ Perfluorinated Sulfonic Acids with Extrapolation to C₁₆

New ideal-gas thermochemistry C^°(T), H°(T), S°(T), and G°(T) are predicted for 53 species involved in the thermal destruction of perfluorinated sulfonic acids (PFSAs) ranging from C₂ to C₈ in perfluorinated alkyl chain length. Species were selected by considering both the pyrolytic and oxidative pathways of PFSA destruction. After the sulfur-containing moieties are removed, subsequent reactions largely involve species from a prior set of thermochemistry for the thermal destruction of perfluorinated carboxylic acids (Ram et al., J. Phys. Chem. A, 2024, 128, 7, 1313-1326). Enthalpies of formation at 0 K are computed using a new isogyric reaction scheme. Rigid-rotor harmonic-oscillator partition functions were calculated over a 200-2500 K temperature range using rovibrational properties at G4 (≤C₃S₁ species) and M06-2X-D3(0)/def2-QZVPP (≥C₄S₁ species), employing the 1D hindered rotor approximation to correct for torsional modes. Seven-coefficient NASA polynomial fits are reported in standardized formats. Bond dissociation energies and important reaction equilibria are examined to provide insights into the reactivity of potentially persistent species. Extrapolated NASA polynomials are also systematically predicted for 126 species larger than C₈/C₈S₁ in size, allowing reasonably accurate estimates of thermochemistry without the need for expensive electronic structure calculations.