Limits...
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 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.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.


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


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.


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 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.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.