Kinetics of ligand exchange reaction of Cu(II)-ammine complex with poly(vinyl alcohol) in aqueous solution

Abstract

The kinetics of the ligand exchange reaction of the Cu(II)-ammine complex with poly(vinyl alcohol) (PVA) has been studied by a stopped-flow method at pH 9–10, at μ=0.1 (NH 4Cl) and at 25°C. The reaction is initiated by the formation of unstable [Cu(NH 3) 3] 2+ by the attack of H + on Cu(II)-ammine complex, and proceeds through the mixed complex {[Cu(NH 3) 3(O−PVA)] 2+}. This step may be rate-determining, followed by a rapid reaction. Finally, the Cu(II) ion is taken up by PVA. The rate is given by d[Cu(II)−PVA]/d t=k[H +]{[Cu(NH 3) 4] 2+}[PVA]/[NH 4Cl], where k=k 1 + k′ 2[H +], k 1=4.25× 10s −1 and k′ 2=5.20× 10 11l mol −1s −1.