Abstract: | The kinetics of base hydrolysis of (αβ S)-(o -methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: kobs = kOH[OH?], in the range 0.05 ? [OH?]T, mol dm?3 ? 1.0, I = 1.0 mol dm?3, and 20.0–40.0°C. At 25°C, kOH = 13.4 ± 0.4 dm3 mol?1 s?1, ΔH≠ = 93 ± 2 kJ mol?1 and ΔS≠ = 90 ± 5 JK?1 mol?1. Several anions of varying charge and basicity, CH3CO2?, SO32?, SO42?, CO32?, C2O42?, CH2(CO2)22?, PO43?, and citrate3? had no effect on the rate while phthalate2?, NTA3?, EDTA4?, and DTPA5? accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X-100) micelles, however, retarded the reaction, the effect being in the order SDS> CTAB > Triton X-100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo-phases which control the rate are discussed. © 1994 John Wiley & Sons, Inc. |