In the Classroom
edited by
William F. Coleman
JCE Featured Molecules
Wellesley College Wellesley, MA 02481
Molecular Models Candy Components April Featured Molecules This month’s Featured Molecules come from the paper by Fanny K. Ennever on using candy to illustrate various principles (p 615). They include sucrose and the invert sugar that results from the hydrolysis of sucrose. Students should look for structural similarities between sucrose and the hydrolysis products glucose and fructose, and verify that all three are indeed hydrates of carbon. They should also inspect the models to see whether the position of the substituents in the five and six membered rings are the same in the sucrose and in the hydrolysis products. Also included are two esters important in fruit flavoring of candies. Flavor and aroma are inexorably intertwined in the taste experience and no single compound is responsible for that experience. Methyl cinnamate, included here, is one of over 100 esters, and over 300 compounds, involved in the taste of strawberries (1). Isoamyl acetate is a major component of the taste of bananas. Lastly, chocolate—perhaps nothing else need be said. There is a great deal of confusion in the popular press and on the internet between theobromine, found in cocoa beans, and caffeine. Both molecules are included here and students should easily see why the two might be confused. Consequently there are many exaggerated claims about caffeine in chocolate. An interesting assignment would be for teams of students to find reliable data on the physiological effects of these similar molecules, and to find good analyses on the actual level of caffeine in cocoa beans, versus the amount added in the candy production process, if any.
www.JCE.DivCHED.org
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glucose
methyl cinnamate
Fully manipulable (Chime and Jmol) structures of candy components and other molecules in the collection are available at the JCE Digital Library Web site: http://www.JCE. DivCHED.org/JCEWWW/Features/MonthlyMolecules/2007/Apr/ Literature Cited 1. Aharoni, A. et al. Plant Cell. 2000, 12, 647–662.
Vol. 84 No. 4 April 2007
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Journal of Chemical Education
621
