Abstract
The kinetics of the dissociation of the five-coordinate complex [tris(2-dimethylaminoethyl)amine-NN′-N″N‴] cobalt(II) in solutions of chloroacetic acid have been studied using stopped-flow spectrophotometry. Solvents used were dimethylformamide, aqueous dimethylformamide, dimethyl sulfoxide, aqueous dimethyl sulfoxide, and acetonitrile. The rate of reaction of the principal step in the dissociation path is proportional to the complex concentration; the first order rate constants 1.0 mol dm −3 chloroacetic acid in the presence of 1.0 mol dm −3 sodium perchlorate at 298 K are 18.4, 4.49, 4.05, and 2.40 sec −1 in dimethylformamide, dimethyl sulfoxide, acetonitrile, and water, respectively. The reaction rate profiles as a function of water concentration in aqueous dimethylformamide and aqueous dimethyl sulfoxide are similar; a broad maximum rate is observed in the 2–10% water range at 298 K. A consistent trend is found for dissociation of the complex in aqueous dimethylformamide solutions of 1.0 mol dm −3 and 0.25 mol dm −3 perchloric acid. A slower step in the dissociation is detectable in nonaqueous solvents but cannot be characterized reliably. These results together with the enthalpies and entropies of activation at 298 K are considered in terms of the possibilities of dissociative and associative reaction pathways.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call