Table 2. All experimental data discussed above are summarized. Beside the relative, calculated external pK_a values, all experimentally obtained parameters, such as the internal acidity of the CPAs (obtained from ¹⁵N chemical shift and ¹J_NH coupling constant) for both E- and Z-complexes, the association constants K_a of the binary complexes as well as the E- to Z isomerisation rates k_iso are given. For the sake of completeness also the AREA (θ) values were added.31 The influence of all these parameters on the relative reaction rate was investigated. TiPSY does not follow the trends observed for the other catalysts TRIP, TRIM and TRIFP (TiPSY is visualized with grey bars).