Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions
The reactions of 2,4- and 2,5-dihydroxybenzoic acids (dihydroxybenzoic acid, DHBA) with chromium(III) in weak acidic aqueous solutions have been shown to take place in at least two stages. The first stage of the reactions has an observed rate constant k1(obs)=k1[DHBA]+C and the corresponding activat...
Saved in:
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2010-01-01
|
| Series: | Bioinorganic Chemistry and Applications |
| Online Access: | http://dx.doi.org/10.1155/2010/832768 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832559350120448000 |
|---|---|
| author | Kimon Zavitsanos Athinoula L. Petrou |
| author_facet | Kimon Zavitsanos Athinoula L. Petrou |
| author_sort | Kimon Zavitsanos |
| collection | DOAJ |
| description | The reactions of 2,4- and 2,5-dihydroxybenzoic acids (dihydroxybenzoic acid, DHBA) with chromium(III) in weak acidic aqueous solutions have been shown to take place in at least two stages. The first stage of the reactions has an observed rate constant k1(obs)=k1[DHBA]+C and the corresponding activation parameters are ΔH1(2,4)≠=49,5 kJ/mol−1, ΔS1(2,4)≠=−103,7 J mol−1 K−1, ΔH1(2,5)≠=60,3 kJ/mol−1, and ΔS1(2,5)≠=−68,0 J mol−1 K−1. These are composite activation parameters and the breaking of the strong intramolecular hydrogen bonding in the two ligands is suggested to be the first step of the (composite) first stage of the reactions. The second stage is ligand concentration independent and is thus attributed to a chelation process. The corresponding activation parameters are ΔH2(2,4)≠=45,13 kJ/mol−1, ΔS2(2,4)≠=−185,9 J mol−1 K−1, ΔH2(2,5)≠=54,55 kJ/mol−1, and ΔS2(2,5)≠=−154,8 J mol−1 K−1. The activation parameters support an associative mechanism for the second stage of the reactions. The various substitution processes are accompanied by proton release, resulting in pH decrease. |
| format | Article |
| id | doaj-art-6074e5596baf41d39729226bc3a60aba |
| institution | Kabale University |
| issn | 1565-3633 1687-479X |
| language | English |
| publishDate | 2010-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Bioinorganic Chemistry and Applications |
| spelling | doaj-art-6074e5596baf41d39729226bc3a60aba2025-02-03T01:30:11ZengWileyBioinorganic Chemistry and Applications1565-36331687-479X2010-01-01201010.1155/2010/832768832768Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous SolutionsKimon Zavitsanos0Athinoula L. Petrou1Laboratory of Inorganic Chemistry, Department of Chemistry, University of Athens, Panepistimioupolis, 15771 Athens, GreeceLaboratory of Inorganic Chemistry, Department of Chemistry, University of Athens, Panepistimioupolis, 15771 Athens, GreeceThe reactions of 2,4- and 2,5-dihydroxybenzoic acids (dihydroxybenzoic acid, DHBA) with chromium(III) in weak acidic aqueous solutions have been shown to take place in at least two stages. The first stage of the reactions has an observed rate constant k1(obs)=k1[DHBA]+C and the corresponding activation parameters are ΔH1(2,4)≠=49,5 kJ/mol−1, ΔS1(2,4)≠=−103,7 J mol−1 K−1, ΔH1(2,5)≠=60,3 kJ/mol−1, and ΔS1(2,5)≠=−68,0 J mol−1 K−1. These are composite activation parameters and the breaking of the strong intramolecular hydrogen bonding in the two ligands is suggested to be the first step of the (composite) first stage of the reactions. The second stage is ligand concentration independent and is thus attributed to a chelation process. The corresponding activation parameters are ΔH2(2,4)≠=45,13 kJ/mol−1, ΔS2(2,4)≠=−185,9 J mol−1 K−1, ΔH2(2,5)≠=54,55 kJ/mol−1, and ΔS2(2,5)≠=−154,8 J mol−1 K−1. The activation parameters support an associative mechanism for the second stage of the reactions. The various substitution processes are accompanied by proton release, resulting in pH decrease.http://dx.doi.org/10.1155/2010/832768 |
| spellingShingle | Kimon Zavitsanos Athinoula L. Petrou Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions Bioinorganic Chemistry and Applications |
| title | Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions |
| title_full | Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions |
| title_fullStr | Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions |
| title_full_unstemmed | Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions |
| title_short | Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions |
| title_sort | kinetics and mechanisms of the chromium iii reactions with 2 4 and 2 5 dihydroxybenzoic acids in weak acidic aqueous solutions |
| url | http://dx.doi.org/10.1155/2010/832768 |
| work_keys_str_mv | AT kimonzavitsanos kineticsandmechanismsofthechromiumiiireactionswith24and25dihydroxybenzoicacidsinweakacidicaqueoussolutions AT athinoulalpetrou kineticsandmechanismsofthechromiumiiireactionswith24and25dihydroxybenzoicacidsinweakacidicaqueoussolutions |