| An (17)O-NMR Study of the Exchange of Water on AlOH(H(2)O)(5)(2+)(aq). | |
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MedLine Citation:
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PMID: 11670638 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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The pH-dependence of the rate of water exchange between hydrated aluminum complexes and bulk aqueous solution is reported from variable-temperature dynamic (17)O-NMR measurements. Over the temperature range 298-348 K, the pseudo-first-order rate coefficient for exchange at any given temperature, is described by = + [H(+)](-1), where is the rate coefficient for exchange of inner-sphere water molecules with bulk solution for the Al(H(2)O)(6)(3+)(aq) complex at that temperature, and [H(+)](-1) is the pH-dependent contribution to from the first hydrolysis product: AlOH(H(2)O)(5)(2+)(aq). The rate parameters are = 1.3 s(-1), DeltaH(1)() = 84.7 kJ.mol(-1), DeltaS(1)() = 41.6 J.mol(-1).K(-1) (from 6); and = 7.2 x 10(-2) M.s(-1), DeltaH(2)() = 90.4 kJ.mol(-1), DeltaS(2)() = 36.6 J.mol(-1).K(-1) (this work). From this result we obtained the activation parameters for water exchange on the AlOH(H(2)O)(5)(2+)(aq) complex: = 3.1 x 10(4) s(-1), DeltaH() = 36.4 kJ.mol(-1), DeltaS() = -36.4 J.mol(-1).K(-1). Thus, deprotonation of an inner-sphere water in Al(H(2)O)(6)(3+)(aq) enhances by a factor of approximately 10(4) the lability of other inner-sphere oxygens. This labilizing effect of hydroxyl is much larger than for other geochemically important ligands, including fluoride. |
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Authors:
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Jan P. Nordin; David J. Sullivan; Brian L. Phillips; William H. Casey |
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Publication Detail:
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Type: JOURNAL ARTICLE |
Journal Detail:
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Title: Inorganic chemistry Volume: 37 ISSN: 1520-510X ISO Abbreviation: Inorg Chem Publication Date: 1998 Sep |
Date Detail:
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Created Date: 2001-Oct-23 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0366543 Medline TA: Inorg Chem Country: - |
Other Details:
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Languages: ENG Pagination: 4760-4763 Citation Subset: - |
Affiliation:
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Department of Land, Air and Water Resources; Chemical Engineering and Materials Science; and Department of Geology, University of California, Davis, California 95616. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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