Premium
Base hydrolysis of (αβ S)‐( o ‐methoxy benzoato) (tetraethylenepentamine) cobalt(III) ion: A comparative study of the role of ion pairs and micelles
Author(s) -
Acharya Achyuta N.,
Dash Anadi C.
Publication year - 1994
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550260702
Subject(s) - chemistry , micelle , aqueous solution , hydrolysis , cationic polymerization , cobalt , kinetics , inorganic chemistry , base (topology) , reaction rate constant , ion , medicinal chemistry , polymer chemistry , organic chemistry , mathematical analysis , physics , mathematics , quantum mechanics
The kinetics of base hydrolysis of (αβ S)‐( o ‐methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: k obs = k OH [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, k OH = 13.4 ± 0.4 dm 3 mol −1 s −1 , Δ H ≠ = 93 ± 2 kJ mol −1 and Δ S ≠ = 90 ± 5 JK −1 mol −1 . Several anions of varying charge and basicity, CH 3 CO 2 − , SO 3 2− , SO 4 2− , CO 3 2− , C 2 O 4 2− , CH 2 (CO 2 ) 2 2− , PO 4 3− , and citrate 3− had no effect on the rate while phthalate 2− , NTA 3− , EDTA 4− , and DTPA 5− 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.