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  Home > JCE Print > Journal of Chemical Education > Issues > 2007  > February  >
In the Laboratory
JCE Featured Molecules
Molecular Model of Zincon
William F. Coleman
Department of Chemistry, Wellesley College, Wellesley, MA 02481
Cover
February 2007
Vol. 84 No. 2
p. 305

Full Text
The Featured Molecules this month are the tautomeric forms of the colorimetric reagent zincon, used in the paper by Maria Mar Areco, Maria dos Santos Afonso, and Erika Valdman on the bioabsorption of zinc, and by extension other metal ions, by seaweed. The structures presented have been calculated at the DFT/6-31G(d) level using the B3LYP functional. These structures represent energy minima, but not necessarily global minima. The structures could be used as an introduction to the concept of tautomerism, with students being asked to develop a definition of the term based on their observations of the difference(s) in linkage in the two forms. An intramolecular hydrogen bond is found in each structure, and introductory chemistry students could be encouraged to look for these structural features in molecules that are more complex than those typically encountered to introduce hydrogen bonding. More advanced students could use computational techniques to explore the energy differences between the two forms, and compare those differences to the ones observed between more traditional keto/enol examples.
zincon
zincon

Fully manipulable (Chime and Jmol) versions of zincon are available at the JCE Digital Library Web site.

More Information
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Citation
Coleman, William F. J. Chem. Educ. 2007, 84, 305.
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Keywords
Biological Cells; Calorimetry / Thermochemistry; Collaborative / Cooperative Learning; First-Year Undergraduate / General; Hands-On Learning / Manipulatives; Water / Water Chemistry
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History
Created:
Last Updated:
1/9/2007
2/23/2007
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Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.
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