The thermal decomposition of perfluorobutanoic acid (PFBA) was measured in a shock tube. The rate of decomposition was quantified using laser schlieren densitometry (LS) behind the incident shock wave. Experiments were performed with 1% and 2% PFBA dilute in krypton at 30, 60, and 120 Torr over a temperature range of 1400 – 2200 K. A detailed chemical kinetic mechanism was developed to interpret the measured density gradients. RRKM/ME calculations were performed for PFBA decomposition, as well as several product channels. Stationary points were computed using UCCSD(T)-F12b/cc-pVTZ-f12//B2PLYPD3/cc-pVTZ level theory. At low temperatures, the decomposition favors HF elimination to form an 𝛼-lactone intermediate, which immediately dissociates to CO + C2F5CFO. At higher temperatures, C-C bond fission dominates over HF elimination. The most important bond fission channel is C3F7 + CF2C(O)OH, owing to the resonance stabilization of the CF2C(O)OH radical. The channel C4F9 + C(O)OH also is competitive. The CF2C(O)OH radical quickly undergoes 𝛼-scission to form CF2 + C(O)OH. Thus, in both cases, the high-temperature pathway leads to C(O)OH. C(O)OH can decompose to either H + CO2 or OH + CO. In terms of secondary chemistry that contribute to the density gradient, at lower temperatures, the most important secondary reaction is the unimolecular decomposition of C2F5CFO. At higher temperatures, the signal is dominated by the well-skipping reaction CF3 + OH CF2O + HF. The model is in excellent agreement with the data.
