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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.
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