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Teaching at the Speed of Light

May 26, 2014

Teaching chemistry involves maintaining a working knowledge of the latest research and technology while choosing the best of both to demonstrate to students. This is a challenging task to begin with and can quickly become more daunting, if information is not readily available. The good news is introducing microwave chemistry into your curriculum or devising a course entirely devoted to microwave chemistry doesn’t have to be an insurmountable task.
Using microwaves in teaching laboratories has been well documented in the literature. Publications on experiments to perform and logistically how to move to a microwave-based (or inclusive) curriculum are referenced throughout the literature.1 In addition to the literature, there are several resources available from CEM Corporation to learn more about microwaves and teaching. The CEM website has information from background reading on microwave energy to how to pick the best microwave system to meet your needs and experiments that can be used as-is in a teaching laboratory. The International Conference on Chemistry Education and the Biennial Conference on Chemical Education in August will both feature workshops presented by experts from CEM.
CEM is devoted to introducing current microwave technology from the chemical industry to the classroom. In a soon to be released application note for teaching, students are introduced to microwave heating using examples of the heating mechanisms of dipole rotation and ionic conduction.
dipole_combined.gif ionic_combined.gif
Dipole Rotation Ionic Conduction
Through empirical results and observation, students must draw conclusions about the heating characteristics of varied homogeneous and heterogeneous solutions and the microwave absorptive properties of different molecules by heating samples in a MARS Microwave Reaction System. As an introductory experiment, this note familiarizes students with current microwave instrumentation and prompts them to consider how different solutions behave in a microwave; both points prepare students for more advanced microwave coursework and chemistry troubleshooting.
Previously published experiments2 report a variety of microwave-assisted reactions for the undergraduate chemistry lab. One such example is the multi-step synthesis of stilbene from benzaldehyde.
This sequence demonstrates a number of fundamental transformations which students can perform over a 3-5 week period using the MARS or Discover Microwave Systems. Microwave and green chemistries are the hallmark of the methods employed in this synthesis with reaction times ranging from 10 to 20 minutes at temperatures above reflux, and concepts such as phase transfer catalysis and benign reagents/solvents. During the course of this route, students also gain a strong foundation in instrumentation, with the ability to incorporate the use of IR, 1H-NMR, and 13C-NMR spectroscopy to identify their reaction productions.
The Journal of Chemical Education (like other chemistry journals) has seen an increase in the number of papers published using microwave heating in recent years. One such example comes from the Pohl lab at Iowa State University3. In this paper, students can explore reaction conditions which generate different products from the same starting materials.

ls_newsletter_2014_04_j_chem_edu2.jpgOne of the reaction pathways is a saponification in which oils are converted to soap using both conventional and microwave heating. The other reaction pathway (from the same oil feedstock) is a trans-esterification which converts the sample to biodiesel. The results are compared for conventional and microwave methods (performed in a MARS) and students can appreciate the time savings and energy efficiency of microwave heating.

There are many resources available to both students and teachers in an easy-to-access format. Many experiments are designed to be incorporated directly into the teaching laboratory with few, if any, modifications. All provide a slightly different take on how microwave energy can best be utilized. The possibilities are endless.

1 Some recent example publications from J. Chem. Educ. include: Russell, C.B.; Mason, J.D.; Bean, T.G.; Murphree, S.S.; J. Chem. Educ., 2014, 91, 511−517. Slade, M.C.; Raker, J.R.; Kobilka, B.; Pohl, N.L.B.; J. Chem. Educ. 2014, 91, 126−130. Ison, E.A.; Ison, A.; J. Chem. Educ., 2012, 89, 1575−1577. Jensen, J.; Grundy, S.C.; Bretz, S.L.; Hartley, C.S.; J. Chem. Educ., 2011, 88, 1133–1136. Pohl, N.L.B.; Kirshenbaum, K.; Yoo, B.; Schulz, N.; Zea, C.J.; StreÔ¨Ä, J.M.; Schwarz, K.L.; J. Chem. Educ., 2011, 88, 999–1001. Baar, M.R.; Falcone, D.; Gordon, C.; J. Chem. Educ., 2010, 87, 84-86. Many more are also available. (Note: The above list does not include references to microwave extraction and digestion, which are also prevalent in teaching curriculum.)
2 Leadbeater, N. and McGowan, C.; Clean, Fast Organic Chemistry: Microwave-Assisted Laboratory Experiments. CEM Publishing: Matthews, NC, 2006.
3 Pohl, N. L. B.; Streff, J. M.; Brokman, S.; J. Chem. Educ., 2012, 89, 1053 – 1056.

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