Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate

The kinetics of the aqueous reaction of Cr(III) with either L-glutamic acid or sodium hydrogen L-glutamate at pH 2.46-5.87 have been followed by means of absorbance readings. The rate of formation of the reaction products showed acceleration-deceleration periods, caused by the accumulation and poste...

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Autores: Pérez de Benito, Joaquín F., Nicolàs Rivasés, Joan
Tipo de recurso: artículo
Estado:Versión aceptada para publicación
Fecha de publicación:2018
País:España
Institución:Universidad de Barcelona
Repositorio:Dipòsit Digital de la UB
OAI Identifier:oai:diposit.ub.edu:2445/127697
Acceso en línea:https://hdl.handle.net/2445/127697
Access Level:acceso abierto
Palabra clave:Crom
Cinètica química
Àcid glutàmic
Chromium
Chemical kinetics
Glutamic acid
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spelling Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediatePérez de Benito, Joaquín F.Nicolàs Rivasés, JoanCromCinètica químicaÀcid glutàmicChromiumChemical kineticsGlutamic acidThe kinetics of the aqueous reaction of Cr(III) with either L-glutamic acid or sodium hydrogen L-glutamate at pH 2.46-5.87 have been followed by means of absorbance readings. The rate of formation of the reaction products showed acceleration-deceleration periods, caused by the accumulation and posterior decay of an intermediate in nonnegligible concentration. A double-exponential integrated rate law allowed obtaining two rate constants for each absorbance-time experimental series, associated with the appearance (k1) and decay (k2) of the long-lived intermediate. An increase of the initial concentrations of either hydrogen L-glutamate (apparent kinetic orders < 1) or hydroxide (kinetic orders = 1) ions resulted in an increase of both k1 and k2, but addition of an inert electrolyte (KNO3) resulted in opposite effects on k1 (decrease) and k2 (increase). The experimental activation energies were 83 ± 10 (for k1) and 95 ± 5 (for k2) kJ mol−1. The electronic spectrum of the low reactivity detected intermediate resembled more closely to that of the blue/green reactant than that of the violet reaction product. The low number of protons set free by the complexating hydrogen L-glutamate ligand seems to suggest that some polymerization of the coordinated amino acid (to form a di- or tripeptide) might take place. The available experimental data indicate that the coordination of the organic ligand must be preceded by the breakdown of a strong Cr(III)-H2O chemical bond in the slow steps of the mechanism.Wiley2018info:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionapplication/pdfhttps://hdl.handle.net/2445/127697Articles publicats en revistes (Ciència dels Materials i Química Física)reponame:Dipòsit Digital de la UBinstname:Universidad de BarcelonaInglésVersió postprint del document publicat a: https://doi.org/10.1002/kin.21185International Journal of Chemical Kinetics, 2018, vol. 50, num. 8, p. 591-603https://doi.org/10.1002/kin.21185(c) Wiley, 2018info:eu-repo/semantics/openAccessoai:diposit.ub.edu:2445/1276972026-05-27T06:46:51Z
dc.title.none.fl_str_mv Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
title Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
spellingShingle Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
Pérez de Benito, Joaquín F.
Crom
Cinètica química
Àcid glutàmic
Chromium
Chemical kinetics
Glutamic acid
title_short Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
title_full Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
title_fullStr Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
title_full_unstemmed Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
title_sort Kinetics of the chromium(III)/L-glutamic acid complexation reaction: formation, decay, and uv-vis spectrum of a long-lived intermediate
dc.creator.none.fl_str_mv Pérez de Benito, Joaquín F.
Nicolàs Rivasés, Joan
author Pérez de Benito, Joaquín F.
author_facet Pérez de Benito, Joaquín F.
Nicolàs Rivasés, Joan
author_role author
author2 Nicolàs Rivasés, Joan
author2_role author
dc.subject.none.fl_str_mv Crom
Cinètica química
Àcid glutàmic
Chromium
Chemical kinetics
Glutamic acid
topic Crom
Cinètica química
Àcid glutàmic
Chromium
Chemical kinetics
Glutamic acid
description The kinetics of the aqueous reaction of Cr(III) with either L-glutamic acid or sodium hydrogen L-glutamate at pH 2.46-5.87 have been followed by means of absorbance readings. The rate of formation of the reaction products showed acceleration-deceleration periods, caused by the accumulation and posterior decay of an intermediate in nonnegligible concentration. A double-exponential integrated rate law allowed obtaining two rate constants for each absorbance-time experimental series, associated with the appearance (k1) and decay (k2) of the long-lived intermediate. An increase of the initial concentrations of either hydrogen L-glutamate (apparent kinetic orders < 1) or hydroxide (kinetic orders = 1) ions resulted in an increase of both k1 and k2, but addition of an inert electrolyte (KNO3) resulted in opposite effects on k1 (decrease) and k2 (increase). The experimental activation energies were 83 ± 10 (for k1) and 95 ± 5 (for k2) kJ mol−1. The electronic spectrum of the low reactivity detected intermediate resembled more closely to that of the blue/green reactant than that of the violet reaction product. The low number of protons set free by the complexating hydrogen L-glutamate ligand seems to suggest that some polymerization of the coordinated amino acid (to form a di- or tripeptide) might take place. The available experimental data indicate that the coordination of the organic ligand must be preceded by the breakdown of a strong Cr(III)-H2O chemical bond in the slow steps of the mechanism.
publishDate 2018
dc.date.none.fl_str_mv 2018
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/acceptedVersion
format article
status_str acceptedVersion
dc.identifier.none.fl_str_mv https://hdl.handle.net/2445/127697
url https://hdl.handle.net/2445/127697
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Versió postprint del document publicat a: https://doi.org/10.1002/kin.21185
International Journal of Chemical Kinetics, 2018, vol. 50, num. 8, p. 591-603
https://doi.org/10.1002/kin.21185
dc.rights.none.fl_str_mv (c) Wiley, 2018
info:eu-repo/semantics/openAccess
rights_invalid_str_mv (c) Wiley, 2018
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Wiley
publisher.none.fl_str_mv Wiley
dc.source.none.fl_str_mv Articles publicats en revistes (Ciència dels Materials i Química Física)
reponame:Dipòsit Digital de la UB
instname:Universidad de Barcelona
instname_str Universidad de Barcelona
reponame_str Dipòsit Digital de la UB
collection Dipòsit Digital de la UB
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15.300724

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