Henry's law constants of 2,2,2-trifluoroethyl formate, ethyl trifluoroacetate, and non-fluorinated analogous esters

Henry's law constants of two fluorinated esters [CF3CH2OC(O)H and C2H5OC(O)CF3] and four related non-fluorinated esters [CH3OC(O)H, C2H5OC(O)H, n-C3H7OC(O)H and C2H5OC(O)CH3] were determined at 278–298 K by a column-stripping method. From the van’t Hoff equation of H=H298exp[-ΔHsolR(1T-1298)], the H298 (M atm−1) and ΔHsol (kJ mol−1) values obtained were 0.55±0.04, −39±3 (CF3CH2OC(O)H); 0.09±0.01, −41±5 (C2H5OC(O)CF3); 4.2±0.2, −33±2 (CH3OC(O)H); 3.4±0.2, −38±2 (C2H5OC(O)H); 2.6±0.1, −42±1 (n-C3H7OC(O)H); and 6.0±0.5, −49±3 (C2H5OC(O)CH3), respectively. Errors reported are at 95% confidence levels and represent precision only. Hydrolysis was observed only for C2H5OC(O)CF3. Replacement of CH3 by CF3 decreases H298 values by 6, 11, and 67 times, respectively, for CF3CH2OC(O)H, CF3CH2OC(O)CH3, and C2H5OC(O)CF3, while the differences in the ΔHsol values were small with these substitutions. Sodium chloride salting-out effects are examined for all of the esters. C2H5OC(O)CF3 has the largest salting coefficient (0.74). The estimated lifetime of CF3CH2OC(O)H suggests that dissolution into seawater serves as a tropospheric sink for this compound. On the basis of the solubility and reactivity of the esters studied herein, clouds and the ocean are discussed as possible sinks for the dissolution of tropospheric CF3CF2OC(O)H, which is an atmospheric oxidation product of a substitute for hydrofluorocarbons as CF3CF2OCH3.