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How to Do and Think About Organic Chemistry...

“The Shrewd Guess: Can a Software System Assist Students in Hypothesis-Driven Learning for Organic Chemistry?” by Michael Evans, et al., Journal of Chemical Education (2020), https://doi.org/10.1021/acs.jchemed.0c00246.

“Reaction of Diphenyldiazomethane with Benzoic Acids in Batch and Continuous Flow” by Pamela Pollet, Charles Liotta, Hui Zhu, et al., Journal of Chemical Education (2020), https://doi.org/10.1021/acs.jchemed.0c01044

The Journal of Chemical Education is the world’s premier scientific journal for the teaching of chemistry and related subjects. The School of Chemistry and Biochemistry publishes regularly in this journal, sharing with the larger community examples of innovations for bringing excitement and understanding of our molecular world to students at many levels. Two recent publications highlight advances in experimental and conceptual aspects of organic chemistry from our department.

Drawing and visualizing reaction mechanisms are perennial challenges for students of introductory organic chemistry. Student errors can range from misunderstanding “the rules of the game” to making chemically dubious “moves.” Research has shown that students often view organic reaction mechanisms as monolithic instead of composed of a small set of transferrable and recurring elementary steps. As a result, students often attempt to memorize mechanisms in their entirety instead of breaking them down into “chunks,” in the process missing similarities between analogous mechanisms. Recognition of these analogies helps experts compress the massive body of information associated with organic reaction mechanisms to a manageable size; with proper training, students can apply the same strategy.

Professor Michael Evans is part of a team that developed and tested the “Mechanisms” smartphone app, a tool for exploring how organic chemistry works by dragging valence electrons around in chemical CE_1.jpgstructures on a touch-screen interface. The app constrains the “rules of the game” to promote learning mechanism-drawing conventions and employing chemical mechanistic reasoning. The paper, authored by Dr. Julia Winter and colleagues at Alchemie Solutions, the company that developed the app, and Prof. Evans and colleagues at three other colleges and universities, describes the development and implementation of the Mechanisms app in a variety of university contexts, including an organic chemistry course at Georgia Tech. Decision trees generated as students moved electrons in the app were studied in an effort to understand how students use it. Dr. Evans used Mechanisms both to provide additional practice in class with chemical reactions that students had already seen, and to introduce new mechanisms in class, placing the dynamic representation in the app before the static curved-arrow representation depicted in the textbook. Students found the tool quite useful, and it is expected to find increasing application at Georgia Tech and elsewhere.

Several years ago, Professors Pamela Pollet and Charles Liotta created the ChemFlow Vertically Integrated Projects (VIP) course at Georgia Tech. This class – the only one of its kind in the United States – brings together diverse students to learn and practice a new way to perform organic chemical reactions. To increase safety and decrease the use of expensive and environmentally damaging solvents and reagents, the traditional methods of stirring things up in big vats (“batch chemistry”) has to change. The answer is to bring chemical reactants together in solutions that flow through tubes. In this way, it becomes much easier to control many of the complex factors that go into making molecules at any scale – temperature, concentration, time, purification, and recycling of solvents and catalysts. This method, called “continuous flow chemistry,” is one of the most important developments in the area of green chemistry and chemical engineering, at the forefront of a cultural change for the future of the chemicals industry. Students have very few opportunities to learn about it in most programs. Thanks to the ChemFlow VIP, this is not the case at Georgia Tech.

Students in this course seek to answer questions such as: How do we deliberately design in-flow chemical transformations? How do we think about batch data vs. flow data? How do we experimentally transfer batch processes to flow processes? How do we make the most of in-flow precise control over mixing, heat exchange and residence time? Which limitations and precautions must be considered when designing continuous multi-step syntheses?

The paper in J. Chem. Ed. describes one example of original research conducted by teams of student CE_2.jpgpeers in chemistry, chemical engineering, and mathematics. Interacting with post-doctoral associates, research faculty, and instructional faculty, the students studied a reaction that uses a highly reactive reagent. This material would be dangerous to handle in large quantities in a traditional batch process. Here, however, the flow process renders the process safe and scalable. The students varied many of its parameters, informed by engineering calculations and experimental measurements, to gain sophisticated understanding of the physical chemistry, organic reactivity, and analytical chemistry involved. The multi-disciplinary team also required the practice of good communication and interpersonal skills, along with time and project management. The result was a custom-made reactor, a process that is now part of a new experiment in an upper-division organic chemistry laboratory course, and invaluable experience in the future of chemical reactions at industrial scale.

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