Problematizing Reactions to Create Guided Inquiry Labs

A simple way to develop a guided-inquiry type laboratory experiment from a “classic” laboratory experiment is to create some question that the experimental procedure will help to answer. I tried this with the classic Diels-Alder anthracene + maleic anhydride this semester. Instead of coming out and telling the students that the product would be 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic anhydride (also called 9,10-dihydroanthracene-9,10-alpha,beta-succinic acid anhydride), I told the students to identify the possible s-cis diene Diels-Alder addition sites on anthracene. The product analysis should, therefore, indicate which addition site is favored by the reaction. In the following structure the s-cis dienes would be [6,7,8,8A] for example. It turns out there are 5 different dienes which would give three different products after maleic anhydride addition.

anthracene1

The product analysis should indicate which addition site is favored by the reaction. This “problematization” may be a bit contrived since a GOOGLE search will quickly come up with the favored product. However, the possibility of alternative products at least warrants a careful interpretation of the spectroscopic data.

There is an interesting twist to the story. It turns out that the 1H and 13C NMR spectra of the highly symmetrical product are rather challenging (given the level of NMR expertise of Organic Chemistry students in general and this Organic Chemistry instructor in particular). More details can be found on the OChemOnline “Have you done this lab?” wiki page.

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One Comment

  1. asghari hassan
    Posted March 17, 2009 at 8:40 am | Permalink

    hi
    i am a student of organic chemistry in iran.


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