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An Azulene-Based Discovery Experiment: Challenging Students To Watch for the "False Assumption"

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Charles M. Garner

Department of Chemistry, Baylor University, Waco, TX 76798

J. Chem. Educ., 2005, 82 (11), p 1686

DOI: 10.1021/ed082p1686

Publication Date (Web): November 1, 2005

Section:

History, Education, and Documentation

Abstract

A discovery-based organic laboratory experiment designed to challenge student's assumptions is described. The students are first taught that the trifluoroacylation of azulene followed by treatment with hydroxide yields azulene-1-carboxylic acid, then are told that they will be using 4,6,8-trimethylazulene for reasons of cost and availability. Trimethylazulene undergoes trifluoroacylation normally, but subsequent treatment with base causes a cyclization to yield an alcohol still containing the trifluoromethyl group. There are abundant inconsistencies between the "expected" structure and the color, solubility, polarity, and NMR spectra of the product. Significant learning occurs as the students interpret their data. This exercise results in the students being much more observant and critical of their results, particularly with respect to interpretation of their NMR spectra. This experiment is appropriate for undergraduate organic students who have enough NMR interpretation skills to recognize the structural significance of an AB pattern and requires 2 hours or less in each of two lab periods.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Organic Chemistry

Keywords (Pedagogy):

Inquiry-Based / Discovery Learning

Keywords (Subject):

Aromatic Compounds

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