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In the Laboratory
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JCE Featured Molecules
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Molecular Model of Creatine Synthesis
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William F. Coleman
Department of Chemistry, Wellesley College, Wellesley, MA 02481
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November 2006
Vol. 83 No. 11
p. 1657
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| Full Text |
| The featured molecules for this month come from the paper by Andri Smith and Paula Tan on the synthesis of creatine in introductory organic chemistry. This synthesis is sufficiently straightforward to be used in non-majors and general chemistry courses. The structures illustrate some of the limitations associated with the computation of molecular structure. The two adenosine phosphates ADP and ATP exhibit a large number of conformations due to rotation of the adenine system around the bond to the ribose ring, multiple rotational conformations in the phosphate groups, the ionic state of the compound, and the interaction with the solvent or another species such as creatine. The structures that are given for ADP and ATP are derived from PM3MM calculations and are very similar to those derived using the UFF force field. Sarcosine, creatine, and creatine phosphate were treated using the model chemistry B3LYP/6-31+G(d). Perhaps the most interesting structural feature is found in the small molecule cyanamide.
Observant students might notice in the Web-based structure that the NCN grouping in cyanamide is non-linear, with an angle of about 177°. This is found for essentially all levels of theory we examined up through the G2 combined model. For students who do notice this deviation from linearity it is useful to ask them whether they are surprised, ask them to defend their answer, send them to the literature to see whether such behavior is seen for cyanamide in other phases (it is), and finally to speculate on possible explanations for the observed non-linearity.
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creatine |
adenosine triphosphate |
Fully manipulable (Chime and Jmol) versions of creatine, phosophocreatine, ADP, ATP, cyanamide, and sarcosine, as well the other molecules in the collection are available at the JCE Digital Library Web site.
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| More Information |
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Citation |
Coleman, William F. J. Chem. Educ. 2006 83 1657.
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Keywords |
High School / Introductory Chemistry; Internet / Web-Based Learning; Molecular Modeling; Molecular Properties / Structure
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History |
Created:
Last Updated: |
9/19/2006
9/20/2006
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 Caution! | | 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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