Determination of Rate Constants for Aqueous Reactions of HCFC‐123 and HCFC‐225ca with OH− Along with Henry's Law Constants of Several HCFCs

Henry's law constants of six kinds of hydrochlorofluorocarbons (HCFCs) were determined at 313–353 K by means of a phase‐ratio variation headspace method: and (K_H³⁵³ in M atm^?1, ΔH_sol in kJ mol^?1) = (0.0070 ± 0.0006, –23 ± 2), (0.0038 ± 0.0011, –22 ± 10), (0.0065 ± 0.0007, –21 ± 3), (0.0026 ± 0.0007, –23 ± 8), (0.0016 ± 0.0003, –30 ± 4), and (0.0022 ± 0.0003, –25 ± 4), respectively, for HCFC‐141b (CH₃CCl₂F), HCFC‐142b (CH₃CClF₂), HCFC‐123 (CF₃CHCl₂), HCFC‐124 (CF₃CHClF), HCFC‐225ca (CF₃CF₂CHCl₂), and HCFC‐225cb (CClF₂CF₂CHClF). Errors represent two standard deviations only for the fitting. The decay of headspace partial pressures of these HCFCs via hydrolysis was discerned only for CF₃CHCl₂ and CF₃CF₂CHCl₂ under the experimental conditions examined. Rate constants (k_OH– in M^?1 s^?1) for aqueous reactions of CF₃CF₂CHCl₂ and CF₃CHCl₂ with OH^? at 313–353 K were determined to be and , respectively, from monitoring changes in headspace partial pressure over prescribed concentrations of aqueous NaOH as a function of the headspace time duration and concentration of aqueous NaOH. The calculations performed included consideration of gas–water equilibrium and hydrolysis at both headspace and room temperatures. The calculation for CF₃CHCl₂ also included consideration of salting‐out effects: The salting coefficient of NaCl on a natural log basis was determined to be 0.36 ± 0.06 M^?1, and this value was used for consideration of the salting‐out effect of NaOH. Whereas the activation energy for CF₃CF₂CHCl₂ was greater than that for CF₃CHCl₂, the k_OH– value at 353 K of CF₃CF₂CHCl₂ was 10³ times larger than that of CF₃CHCl₂, indicating that reaction mechanisms for these two HCFCs differed from each other. The aqueous reaction of CF₃CF₂CHCl₂ with OH^? was found to proceed through dehydrofluorination on the basis of detection of CF₃CF?CCl₂ as a primary degradation product of the reaction and proportionality of the rate constants to both concentrations of CF₃CF₂CHCl₂ and OH^?.