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Identification of a Conjugated Diene from Eucalyptus Oil

Page history last edited by PBworks 15 years, 12 months ago

 

Summary of procedure:

The reaction mixture of Eucalyptus (essential) oil, maleic anhydride, and ethyl ether was refluxed for 30 minutes.

After refluxing the Diels-Alder product precipitates.

Recrystallization is done from ethanol.

The product (crude and recrystallized) was analysed by GC and melting point.

 

Positive

+The Diels-Alder reaction is one of those quintessential reactions that should be emphasized in the OChem curriculum.

+I liked the interface with natural products as well as the inquiry potential. The experiment presents four possible dienes in Eucalyptus oil. The essential oil is reacted with maleic anhydride and identification of the product by melting point reveals which diene was prevalent in Eucalyptus oil.

+Smells nice.

 

Neutral

±The Maleic Anhydride does not dissolve until well into the refluxing period.

 

Negative

-The use of ether as a solvent is less-than-ideal here. We had a small fire in the lab when a student removed the round bottom from the reflux condenser.

- Melting point is a mundane way to characterize a product. GC or even IR are more appropriate here. Curiously, the melting points that students' recorded seemed to indicate a higher purity of product (127-129) vs Maliec anhydride (53) than did the GC.

 

Inquiry & Extension Ideas.

●This could possibly be done as a “solventless” reaction. The cineole in Eucalyptus oil could play the part of solvent.

●The inquiry aspect could be transferred to a “unknown” format. An unknown diene is reacted with maleic anhydride and the product characterized to reveal the structure of the diene.

 

Student Comments 2008: Eucalyptus Oil

 

Photo Gallery:

 

 

 

 

Comments (1)

Anonymous said

at 1:58 pm on Mar 8, 2008

The latest GC-FID chromatograms show that the students are mostly getting Maleic Anhydride as a "product."

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