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HYDROFLUOROCARBON-236FA 15 Common name: HFC-236fa Chemical name: 1,1,1,3,3,3-hexafluoropropane Synonyms: Hexafluoropropane; 2,2-Dihydrohexafluoropropane CAS number: 690-39-1 Structural formula: CF3CH2CF3 Description: Colorless gas Molecular weight: 152.01 Boiling point: -0.7°C Melting point: -93.6°C Density and specific gravity: 1.370 g/cc Vapor pressure: 36 psia at 25°C (calculated) Conversion factors: 1 mg/m3= 0.16 ppm; 1 ppm = 6.22 mg/m3 TOXICOKINETICS Using tissues obtained from male rats, Vinegar et al. (1995) determined tissue and air partition coefficients for HCF-236fa by vial equilibration. Coefficients were determined for blood/air, liver/air, fat/air, gut/air, rapidly perfused tissue/air, and slowly perfused tissue/air in incubations of 3 hr at 37°C with 800 parts per million (ppm) of HFC-236fa. The partition coefficients (mean ± standard deviation of 12 determinations) were found to be 0.49 ± 0.04 (blood/air), 0.56 ± 0.06 (liver/air), 3.69 ± 0.56 (fat/air), 0.56 ± 0.06 (gut/air), 0.56 ± 0.06 (rapidly perfused tissues/air), and 0.87 ± 0.08 (slowly perfused tissues/air). Gas-uptake experiments were performed by Vinegar et al. (1995) by exposing three male rats for 6 hr to HFC-236fa via inhalation at concentrations of 100, 530, 2350, 7300, and 18,000 ppm. Loss runs, tests performed without rats to determine the loss rate of HFC-236fa from the chamber, showed percent losses of 0.38% ± 0.07% to 2.85% ± 1.40% per hr, and loss runs with animals in the chamber ranged from 1.57% to 11.77%. For both situations, loss of HFC-236fa from exposure chambers was greatest at lower concentrations. Humidity levels, initially thought to be affecting loss rates, were found to have no appreciable effect on the loss of the test material. The role of carbon dioxide in the inexplicable loss of test material was considered but not investigated. Inhalation uptake of HFC-236fa by rats was
