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  Home > JCE Print > Journal of Chemical Education > Issues > 2005  > June  >
Information • Textbooks • Media • Resources
Molecular Modeling Exercises and Experiments
Quantitative Thermodynamic Descriptions of Aromaticity. A Computational Exercise for the Organic Chemistry Laboratory
Terrence Gavin
Department of Chemistry, Iona College, New Rochelle, NY 10801
Cover
June 2005
Vol. 82 No. 6
p. 953
Abstract
This article describes an exercise that enables students to establish a quantitative scale of aromaticity via computer-driven quantum mechanical calculations using Spartan software. The method utilizes a group of analogous isodesmic reactions from which the energy difference between two isomeric cyclic polyenes is calculated from their optimized geometries. The energy differences found are used to characterize structures as aromatic, nonaromatic, or antiaromatic depending on the value obtained. A representative group of structures, including hydrocarbons, hydrocarbon ions, and heterocycles are studied. The exercise is designed for students in their first course in organic chemistry and can be completed in approximately 3–4 hours making it suitable for the organic laboratory. Hückel’s rule is illustrated using classic examples of aromatic and antiaromatic compounds. In addition, the computational model used is examined by comparison with other potentially useful models.
Supplement
A student version of the exercise and three data tables are available.
*  Contents JCE2005p0953W.doc (Microsoft Word)
*  Download
JCE2005p0953W.pdf

JCE2005p0953W.zip
More Information
*  Citation
 Gavin, Terrence. J. Chem. Educ. 2005 82 953.
*  Keywords
 Aromatic Compounds; Computational Chemistry; Computer-Based Learning; Heterocycles; Molecular Modeling; Organic Chemistry; Second-Year Undergraduate; Thermodynamics; Upper-Division Undergraduate
*  History
 Created:
Last Updated:		 April 27, 2005
May 6, 2005
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