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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 11, Number 4
BKCSDE 11(4)
April 20, 1990 

Kinetic Investigation on the Reaction between Cu(Ⅱ) and Excess D-penicillamine in Aqueous Media
Yong-Hwan Lee, Sung-Nak Choi*, Mi-Ae Cho, Yong-Kyu Kim
The kinetics and mechanism of reduction of Cu(Ⅱ) with an excess D-penicillamine have been examined at pH = 6.2 and 0.60M in ionic strength. The reaction at the initial stage is biphasic with a rapid complexation process to give "red" transient complex of [Cu(Ⅱ)(pen)2]2- that is partially reduced to another transient "brown" intermediate. The "brown" intermediate is finally reduced to diamagnetic "yellow" complex, [Cu(I)(Hpen)]n. The final reduction process is pseudo-first order in ["brown" transient] disappearance with k = {k3a + k3b[pen]2-}, where k3a = (5.0±0.8)×10-3sec-1 and k = (0.14±0.02) M-1sec-1 at 25℃. The activation parameters for the [H2pen]-independent and [H2pen]-dependent paths are ΔH≠ = (52±5)kJmol-1, and ΔS≠ = ( - 27±3)JK-1mol-1, and ΔH≠ = (56±2)kJmol-1 and Δ S≠ = ( - 18±0.7)JK-1mol-1 respectively. The nature of "brown" intermediate is not clearly identified, but this intermediate seems to be in the mixed-valence state, judging from the kinetic and spectroscopic informations.
281 - 286
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