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2004
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In the Laboratory
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A Practical Integrated Approach to Supramolecular Chemistry III. Thermodynamics of Inclusion Phenomena
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Jesús Hernández-Benito, M. Pilar García-Santos, Emma O'Brien, Emilio Calle, and Julio Casado
Departamento de Química Física, Universidad de Salamanca, Facultad de Química, E-37008 Salamanca, Spain
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April 2004
Vol. 81 No. 4
p. 540
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| Abstract |
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This is the third in a series of experiments aimed at introducing undergraduate students into the field of supramolecular chemistry. The first of these integrated works ( J. Chem. Educ. 1999, 76, 419) allows measurement of the equilibrium constant of the formation of the inclusion complex of an azo-dye (guest molecule) in α-cyclodextrin (host molecule). In a second experiment ( J. Chem. Educ. 1999, 76, 422), the kinetics of the formation of the inclusion complex was studied. In the present article, we propose an experiment aiming to familiarize students with the thermodynamics of inclusion phenomena. With this in mind, a spectrometric study of the inclusion of the azo-dye Biebrich Scarlet in α-cyclodextrin has been designed. A model implying that the guest molecule is buried within the cavity of α-cyclodextrin through a two-step mechanism is used: the dye (substrate, S) reacts with the α-cyclodextrin, C, in a rapid equilibrium to form the intermediate (CS)*, which then gradually forms the final complex, CS. This experiment should help students: (i) to determine the thermodynamic parameters corresponding to the inclusion reactions, (ii) to calculate some activation parameters, and (iii) to gain insight into the "driving forces" behind inclusion reactions. Additional results obtained with other azo-dyes, which might be useful in practical work with students, are also offered.
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| Supplement |
Instructions for the students and notes for the instructor are available.
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 Contents |
JCE2004p0540W.doc (Microsoft Word)
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| Download |
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| More Information |
Citation |
Hernández-Benito, Jesús; García-Santos, M. Pilar; O'Brien, Emma; Calle, Emilio; Casado, Julio. J. Chem. Educ. 2004 81 540.
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Keywords |
Equilibrium; Intermolecular Forces; Kinetics; Laboratory Instruction; Physical Chemistry; Thermodynamics; UV-Vis Spectroscopy
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History |
Created:
Last Updated: |
March 3, 2004
February 23, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
2004
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April
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540
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