By Maria Karcz, Member-at-Large for the GCI
How does something become second nature to us? How often do you need to repeat an action that was once foreign to you in order for it to start feeling natural to the extent that doing it any other way would make you feel uncomfortable? These are questions that may float through an educator’s mind as they figure out a way to teach the undergraduate student population about green chemistry. Thinking about how to make a reaction more ‘green’ should not be considered an extra step but rather a natural part of the design process. Green chemistry has been around for much longer than the term itself, with catalytic methods such as iron-catalyzed Grignard additions being developed as early as the 1940s simply because iron was cheap, abundant and allowed a higher yielding reaction1. However, the term ‘green chemistry’ still makes some chemists uncomfortable, often because most chemists have received little to no exposure to the relevant principles. Green is often associated with the term ‘environmentally friendly’ which implies that the object or process may have less of a negative impact on the environment. However, green can and should also mean cost savings, waste reduction, and better performance. When those benefits are brought into the green chemistry conversation, the audience suddenly starts to listen.
In the grand scheme of things, the term being used is irrelevant as long as the principles are there. In industry, the synthetic route taken to make an intended product is not as important as having the end goal safely and effectively met. Consequently, academia has opportunities to present new research that may potentially save a lot of money and reduce generated waste through methods such as use of a greener solvent (which costs less to be disposed of and/or less of it is required), or removing steps from the original synthesis. For these reasons, green chemistry needs to have a solid entrance into a chemistry student’s education in order for the development of green reactions to become second nature. New graduates of any discipline often feel there is a disconnect between the things that they learned to do in university versus the things they are expected to do in the workforce. For a chemistry graduate starting out their first job at a pharmaceutical company, the new expectation may be to optimize an existing reaction to use less of a certain toxic solvent, or generate less waste as the company needs to meet new environmental regulations. These are already skills that would be acquired as part of green chemistry training, skills that industry jobs require but may not necessarily be taught in many post-secondary institutions. With the recent addition of green chemistry content into the curricula of certain undergraduate courses and the strong presence of the Green Chemistry Initiative, University of Toronto chemistry graduates are already a step ahead from graduates of other chemistry departments across the country.
University of Toronto chemistry professors Andy Dicks, Barb Morra and Sophie Rousseaux are currently integrating green chemistry into the undergraduate chemistry curriculum. So far, an approach has been adopted where first-students are taught traditionally used reactions and then are exposed to the green alternative that may either be safer, generates less waste, has the best atom economy or all of the above. For example in CHM 249H, a second year organic chemistry laboratory course, the recyclable solvent PEG-400 is used for the catalyzed condensation reaction between 4-nitrobenzaldehyde and 5,5-dimethylcyclohexane-1,3-dione (dimedone) (Figure 1)2.
Figure 1. In this reaction, 2nd year organic chemistry students use solvent PEG-400 to form a tetraketone in its dienol form. The solvent is then recycled for further reactions.
However, before being presented with this lab, the reaction is taught using volatile organic solvents which are toxic and flammable (such as piperidine). Replacement of the solvent (among some other changes such as the refluxing time) is meant to introduce students to the concept of greener alternatives for existing reactions.
In CHM 343H, a third-year organic synthesis lab course, green chemistry case studies are covered in class. Januvia, a green chemistry design award-winning drug for Type-2 diabetes, is one case study discussed to illustrate the importance of developing a green reaction in the pharmaceutical sector, which has the worst E-factor from all industry (the ratio mass of waste per mass of product). Students are also required to complete a green chemistry assignment where they design the synthesis of a target product using literature while trying to make the reaction as green as possible. For example, to generate an amide bond, students need to deduce whether direct coupling with an amine (less waste generated) or peptide coupling (more waste generated) should be used to make the reaction greener.
Starting next year, students in first-year introductory physical chemistry (CHM 135H) will be exposed to real-life green chemistry scenarios such as the use of supercritical carbon dioxide as a green solvent for industrial extractions when learning about phase diagrams. In first year organic chemistry (CHM 136H) they will learn about greener reagents for functional group transformations and some introductory toxicology concepts. Content for these courses has been developed through the departmental Chemistry Teaching Fellowship Program for graduate students. These courses will teach green chemistry concepts to thousands of students each year!
Most undergraduate students fail to realize that green chemistry concepts can be used in the lab or discussed in research papers without any mention of the term itself. When describing what would meet the criteria of a green reaction, terms like ‘low waste production’, ‘high atom economy’ or ‘cost and/or energy effective’ can be used. These terms are far more likely to catch the attention of a target audience, since saving money and creating less waste is always appealing to see in alternatives that have been proposed in place of long-used processes. As an undergraduate it is difficult to know what the future will hold after graduation, but the problem solving and expertise gained from green chemistry training will be applicable in academia, industry, and many other career opportunities. The motive for the use of a certain green reaction will be different but the end product will always be the same, no matter where you go.
Special thanks to Professors Barb Morra, Andy Dicks and Sophie Rousseaux for their contributions to this piece.
References:
- Manley, J.B.; Sneddon, H. Green Chemistry Strategies for Drug Discovery. Royal Society of Chemistry. 2015, pg.55.
2. Stacey, J.M.; Dicks A.P.; Goodwin A.A.; Rush B.M.; Nigam M. Green Carbonyl Condensation Reactions Demonstrating Solvent and Organocatalyst Recyclability. J. Chem. Educ. 2013, 90, 1067-1070.
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