Biodiesel synthesis is an interesting way to introduce transesterification reactions as well as a way to discuss alternative fuels. Biodiesel is synthesized from new vegetable oil by the reaction with methoxide, formed separately from methanol and sodium hydroxide. After the reaction is completed, the mixture must then be left to separate, forming a glycerin and a biodiesel layer. The glycerin layer is pulled off using a separatory funnel and the biodiesel and glycerin layers can be analyzed using IR (or other techniques).
Making biodiesel is quite similar to making soap, but with the added advantage of the product being an alternative fuel. Students are very interested in biodiesel. This experiment might also work well being run side by side with the making of soap as a comparison.
Summary prepared July 2006 by John E. Thompson, Science Division at Lane Community College.
Thompson, J. E. Biodiesel Synthesis, Science Division, Lane Community College, 2006