Organic chemistry is challenging for many undergraduates. One reason is that the subject must be presented in an abstract fashion because of the absence of visual proof of reaction outcomes and mechanisms. Students who cannot translate line art and curved arrow drawings into meaningful portraits of reactions will struggle mightily. Recent developments in the modification of traditional experiments coupled with novel use of glassware and improvements in the photography of chemical reactions make it possible for students to obtain valuable visual evidence. Furthermore, these developments lead naturally to the use of interactive videos as an instructional tool in the classroom. In this presentation we focus on the classical Dieckmann condensation using diethyl adipate to form ethyl 2-oxacyclopentanecarboxylate, a �-keto ester. Using a combination of direct physical evidence, such as formation of the enolate precipitate, and classical qualitative tests, the reaction outcome was demonstrated. The product was confirmed by formation of a yellow precipitate with 2,4-dinitrophenylhydrazine coupled with a negative result with Schiff's reagent, demonstrating the product was a ketone. The �-keto ester was verified by the formation of a dark blue complex with 5% FeCl3 solution. The experiment was expanded to include the decarboxylation of the �-keto ester to form cyclopentanone. Carbon dioxide evolution was illustrated by decolorization of a basic solution of thymolphthalein. The cyclopentanone product was identified by its boiling point obtained while distilling the compound onto 2,4-DNP, Schiff's reagent and FeCl3. The challenges involved in the isolation procedure are discussed along with the potential of the study for interactive learning in the classroom. REU participant Vivian Iglesias was supported by the NSF-REU Site grant No: CHE1156886 to FIU.

Aesthetically appealing reactions in organic chemistry: Dieckmann condensation

247th National Meeting (2014)

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