In the Laboratory edited by
JCE Featured Molecules
William F. Coleman Wellesley College Wellesley, MA 02481
Menthol Stereoisomers July Featured Molecules The JCE Featured Molecules for July come from the paper by Edward M. Treadwell and T. Howard Black on the use of commercially available stereoisomers of menthol to illustrate properties of enantiomers and diastereomers (pages 1046–1048). The paper describes the use of four of the eight possible stereoisomers. Structures of all eight stereoisomers are included in this month’s molecule collection, labeled by the chirality of the three chiral atoms. In addition to the exercises described in the paper, students can be asked to match the appropriate structures to those shown in the paper, or to generate structures for the isomers that are not discussed.
Students may also use the molecule files as input to a computational program such as HyperChem (a product of HyperCube, Inc.; http://www.hyper.com) to calculate a number of chemical and physical properties. For example, they can use a variety of semiempirical and ab initio methods to demonstrate the equality of total energy, heat of formation, and molecular orbital energies for enantiomers, and also show that such equality does not exist for diastereomers. Fully manipulable (Chime) versions of this and other molecules are available at the Only@JCE Online Web site: http://www.JCE.DivCHED.org/JCEWWW/Features/ MonthlyMolecules/2005/Jul
(1R,2S,5R)-(–)-menthol
(1R,2S,5S)-(–)-isomenthol
(1R,2R,5S)-(–)-neomenthol
(1S,2S,5S)-(–)-neoisomenthol
(1S,2R,5S)-(+)-menthol
(1S,2R,5R)-(+)-isomenthol
(1S,2S,5R)-(+)-neomenthol
(1R,2R,5R)-(+)-neoisomenthol
1048
Journal of Chemical Education
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Vol. 82 No. 7 July 2005
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www.JCE.DivCHED.org
