Harvey Mudd College students are designing their own green experiments for use in undergraduate chemistry education. The procedures for the most recently completed experiments, which involve the synthesis of organic molecules such as warfarin, divanillin, and several molecules used as fragrances, have been published in the Journal of Chemical Education.

The three experiments are all notable for their relative safety, environmental friendliness, and lack of hazardous chemical waste.

According to HMC Assistant Professor of Chemistry David Vosburg, who mentored the students designing the experiments, environmental impact is not the only benefit that would compel a college to choose to use these experiments instead of more standard lab procedures.

“The less waste we generate, the better it is for the environment, but also it’s cheaper for disposal,” he said, adding that spending less money on chemical waste disposal means schools can direct their money elsewhere.

According to Vosbure, the designers must make the experiments practical for use in the classroom. These experiments must fit into the curriculum, use chemicals with relatively low toxicity, and allow multiple students to perform the experiment simultaneously.

One of the Harvey Mudd experiments, created for use in an advanced chemistry, organic chemistry, or biochemistry classrooms, involves the synthesis of divanillin from vanillin using only horseradish peroxidase (an enzyme found in horseradish plants) and dilute hydrogen peroxide, with the only by-product being water. Since divanillin enhances the flavor of vanillin (a cooking ingredient found in many kitchen cabinets) by several measures in a blind taste test, the experiment has concrete, real-world applications. The experiment is also much more environmentally friendly and safe than the average chemistry experiment.

“You could essentially drink the reaction if you wanted to, although I wouldn’t recommend it,” Vosburg said.

Another experiment, in which students synthesize warfarin—a compound used as both a rat poison and an anticoagulant—is more complicated. According to the article in Journal of Chemical Education, “we have found that this synthesis of warfarin effectively stimulates students to learn about … green chemistry in the real world context of a widely used drug.” By using small organic molecules as catalysts—where most labs would use expensive or toxic heavy metals—the experimenters were able to take advantage of the “right-handedness” versus “left-handedness” of the catalyst molecule in order to choose the chirality of the product molecule.

This technique can prove useful in drug production. For example, left-handed and right-handed versions of certain drugs are cleared from the body at different rates. Currently, drug companies produce warfarin so that left-handed and right-handed molecules are mixed to make production cheaper. However, if some patients were especially sensitive to the drug or taking other medications, they might want only the left-handed or right-handed version. In these cases, Harvey Mudd’s method of synthesizing only one or the other type of warfarin would be useful.

“This is part of the new trend of personalized medicine,” Vosburg said.

The latest experiment has students synthesizing a variety of fragrant molecules, such as the scents of citronella and geraniums, from just one reactant: citral, oil or lemongrass. These molecules, which are found in perfumes but produced naturally by plants, are then identified by the students using smell and a variety of analytical and instrumental techniques.

Anna Cunningham HM ’11, who joined Vosburg’s lab because she was interested in working to help the environment, presented a poster on the experiment at a meeting of the American Chemical Society last March.

“It was great because some professors came up to me and said … they’d be interested in using it in their labs,” she said. HMC professors used the lab in organic chemistry during Cunningham’s junior year, only a few months after she had finished designing the experiment.

Since the Journal of Chemical Education requires the teaching effectiveness of an experiment to be verified it publishes an article about the experiment, Harvey Mudd students get to use other students as guinea pigs. The experiments have been tried out on Harvey Mudd juniors and freshmen to make sure they work well as teaching tools. Vosburg said he even lets touring prospective students have a go at the divanillin reaction.