The values obtained for log k0, log k25, and log k50 ranged from -0.03 to 10.12, -0.59 to 6.81, and -1.10 to 3.93, respectively (Table , Figure ). Apparently, k0 has the broadest range of these three k's and is the most sensitive to the structural variation of the compounds. However, the CIs of log k0 were broader than those of log k25 and log k50, reflecting the fact that the determination of k25 and k50 values was often an interpolation rather than an extrapolation. In particular, the 95% CIs of log k0 for long-chain compounds determined via eq 3 (e.g., 9Cl-PF3ONS) range over 1 log unit or more, which may raise concerns about their practical use as a property descriptor. For such chemicals, k25 or k50 may serve as an alternative descriptor.