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Kinetic Studies and Mechanism of Hydrogen Peroxide Catalytic Decomposition by Cu(II) Complexes with Polyelectrolytes Derived from L-Alanine and Glycylglycine.

Skounas S, Methenitis C, Pneumatikakis G, Morcellet M - Bioinorg Chem Appl (2010)

Bottom Line: The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media.The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293-308 K.The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands.

View Article: PubMed Central - PubMed

Affiliation: Inorganic Chemistry Laboratory, Department of Chemistry, University of Athens, Panepistimiopolis, 15771 Athens, Greece.

ABSTRACT
The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media. The reactions were of pseudo-first order with respect to [H(2)O(2)] and [L-Cu(II)] (L stands for PAla or PGlygly) and the reaction rate was increased with pH increase. The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293-308 K. A suitable mechanism is proposed to account for the kinetic data, which involves the Cu(II)/Cu(I) redox pair, as has been demonstrated by ESR spectroscopy. The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands.

No MeSH data available.


Related in: MedlinePlus

The variation of the logarithm of the initial rate (vo) versus logarithm of [H+] at different hydrogen peroxide concentrations for the system PAla-Cu(II), [PAla] = 2.0 × 10−3 M, [Cu2+] = 5.0 × 10−4 M. T = 298 K.
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fig3: The variation of the logarithm of the initial rate (vo) versus logarithm of [H+] at different hydrogen peroxide concentrations for the system PAla-Cu(II), [PAla] = 2.0 × 10−3 M, [Cu2+] = 5.0 × 10−4 M. T = 298 K.

Mentions: The dependence of the reaction rates on pH is given in Figure 3. The rates of H2O2 decomposition are pH-dependent. The observed rates {d[H2O2]/dt}t→0obs are very low below pH:8 and strongly increase in the alkaline region. The order was found to be between −0.4 and −0.8 with respect to [H+], depending on the [H2O2]. A possible explanation is discussed forward in the text.


Kinetic Studies and Mechanism of Hydrogen Peroxide Catalytic Decomposition by Cu(II) Complexes with Polyelectrolytes Derived from L-Alanine and Glycylglycine.

Skounas S, Methenitis C, Pneumatikakis G, Morcellet M - Bioinorg Chem Appl (2010)

The variation of the logarithm of the initial rate (vo) versus logarithm of [H+] at different hydrogen peroxide concentrations for the system PAla-Cu(II), [PAla] = 2.0 × 10−3 M, [Cu2+] = 5.0 × 10−4 M. T = 298 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2913805&req=5

fig3: The variation of the logarithm of the initial rate (vo) versus logarithm of [H+] at different hydrogen peroxide concentrations for the system PAla-Cu(II), [PAla] = 2.0 × 10−3 M, [Cu2+] = 5.0 × 10−4 M. T = 298 K.
Mentions: The dependence of the reaction rates on pH is given in Figure 3. The rates of H2O2 decomposition are pH-dependent. The observed rates {d[H2O2]/dt}t→0obs are very low below pH:8 and strongly increase in the alkaline region. The order was found to be between −0.4 and −0.8 with respect to [H+], depending on the [H2O2]. A possible explanation is discussed forward in the text.

Bottom Line: The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media.The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293-308 K.The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands.

View Article: PubMed Central - PubMed

Affiliation: Inorganic Chemistry Laboratory, Department of Chemistry, University of Athens, Panepistimiopolis, 15771 Athens, Greece.

ABSTRACT
The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media. The reactions were of pseudo-first order with respect to [H(2)O(2)] and [L-Cu(II)] (L stands for PAla or PGlygly) and the reaction rate was increased with pH increase. The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293-308 K. A suitable mechanism is proposed to account for the kinetic data, which involves the Cu(II)/Cu(I) redox pair, as has been demonstrated by ESR spectroscopy. The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands.

No MeSH data available.


Related in: MedlinePlus