We have developed an economical and simple laboratory exercise that demonstrates an E1cb mechanism using inexpensive tropic acid and potassium hydroxide. The reaction involves a 40 minute reflux followed by neutralization and recrystallization. Student results generally yield 50 – 70% of pure atropic acid (2-phenylpropenoic acid) product. This exercise involves reflux, neutralization, recrystallization, and melting point analysis. If one chooses to run the NMR on the final product, there is an opportunity to teach about diastereotopic protons on terminal alkenes as well. Both the starting material and final product have no known health hazards and the only solvent used is water. The hazards are confined to the small amount solid potassium hydroxide and dilute hydrochloric acid that are used.

Elimination reaction of tropic acid as a simple example of an E1cb reaction

249th National Meeting (2015)

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