Celebrating the 5-Year Anniversary of the GCI

Celebrating the 5-Year Anniversary of the GCI

By Alex Waked, Co-Chair for the GCI

The Green Chemistry Initiative (GCI) at the University of Toronto was founded back in 2012 – it’s crazy to think that we’ve already reached the 5-year milestone. Before you know it, it’ll be 10 years, then perhaps even 20 years! But before we talk about the future, it’s always a good idea to take a step back and reflect on how we’ve gotten here in the first place. This organization wouldn’t even exist had it not been for the vision of co-founders Laura Hoch and Melanie Mastronardi, with help from many graduate students keen on educating themselves and their peers about sustainable practices. With the help of all the other dedicated GCI members over the years, they helped the GCI grow to the point at which we’re now standing. Being the 5-year anniversary of the GCI, I reached out to all the previous co-chairs and asked them to reflect on their time spent here.

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GCI group photo from 2013

Laura Hoch (Co-Chair from 2012-2015):

I’m so excited to help celebrate the GCI’s 5-year anniversary by sharing some reflections and favorite memories from my time with the group. When I look at all the GCI has done over the past 5 years, I am so happy to see how much impact we’ve had. Within our own department, all the events and initiatives – trivia, seminars, workshops, the waste awareness campaign, and many more – have really raised awareness about green chemistry and made it more tangible. Through our work, we have also helped to inspire other students in Canada and around the world to get active, start their own student groups, and promote green chemistry in their own communities.

It’s really hard for me to pick a favorite event or project that I am most proud of – in my extremely biased opinion, we’ve done way too many awesome things! – but for me one of the moments when it really hit home how much of an impact we were having was at a networking session at the ACS Green Chemistry & Engineering Conference in Washington D.C. Waiting in the food line, I randomly ended up talking to a researcher at DuPont. When I mentioned that I was from U of T, he said “Oh! Are you one of those intrepid students from Toronto?!” and proceeded to describe in detail many of our activities and initiatives. It blew my mind that here was a complete stranger from Delaware, who wasn’t even an academic, who had heard of us and thought what we were doing was great.

I can honestly say that helping to start the GCI was by far the BEST thing I did in grad school. I’ve learned so much and have met so many amazing people through our work. I am so proud of what the GCI has accomplished and I really look forward to seeing what the GCI will do in the years to come!

Melanie Mastronardi (Co-Chair from 2012-2014):

It seems like just yesterday that we started the GCI, I can’t believe it’s been 5 years already! Thinking back to where we started (just a handful of grad students who wanted to learn how to conduct our research more sustainably), I’m so proud of all the GCI has been able to accomplish. From weekly trivia challenges to department seminars to hosting students and speakers from all over at our annual symposium, the GCI has created so many opportunities for students and researchers to learn about green chemistry and how to implement it. It’s also absolutely amazing to hear stories of how we inspired students at other universities to start similar organizations! One of my personal favourite projects was launching the 12 Principles of Green Chemistry video campaign. We’ve come a long way from the first one we filmed in Jes’ kitchen and last time I checked we are only 3 away from completing the full set!

Laura Reyes (Co-Chair from 2014-2016):

I am so grateful and proud to have been a founding member and co-chair for the GCI, and continue to be impressed by everything that the group does. It feels surreal to look back on everything that we have accomplished in only 5 years. The GCI started from the curiosity of a few grad students wanting to know how green chemistry could be applied to our own research, and now the group is well-known and respected throughout the green chemistry community as an example of a student-driven education effort. In that time, the GCI has managed to change the conversation around green chemistry in the UofT chemistry department. Subtle changes have compounded into a larger cultural shift, including anything from curriculum development for undergrad courses and labs (and signing Beyond Benign’s Green Chemistry Commitment!), to faculty members self-identifying as using green chemistry in their work. There is still much progress to be made, of course, but looking back on the accomplishments of the GCI and the professional experience that we all gained in being a part of this, it is hard to not feel proud of every project and event that we organized, starting with our very first seminar on the basics of green chemistry to recently teaching that seminar ourselves at the 100th CSC conference!

GCI group photo 2017

GCI group photo from 2017

Erika Daley (Co-Chair from 2015-2016):

Congratulations to all previous and current members of the Green Chemistry Initiative on its 5th anniversary! I was incredibly proud of all the accomplishments and activities that took place during my time as co-chair, and continue to be delighted by the success of the group. I think the value is especially put into perspective in my career when researchers, faculty, students, and industry employees know of or recognize the GCI and the impact it has had all over North America. While it is impossible for me to pick one particular initiative to highlight here, I think the collective outreach, education, data collection, and subsequent actions of the entire GCI team – from the departmental waste awareness campaign, to the community outreach events, to the undergraduate curriculum development – are all so important and speak volumes to what a group of dedicated student volunteers can accomplish.

Ian Mallov (Co-Chair from 2016-2017):

The 5-year anniversary of the GCI is an opportunity to reflect on our mission and goals. What did we want to accomplish, and what have we accomplished? Personally, I’m most proud of the fact that we have successfully ingrained green chemistry education into the fabric of our department through establishing regular events like symposia, seminars, and trivia, and that we helped encourage the department to sign the Green Chemistry Commitment. Green chemistry education should be fundamental to chemical education – it is our job as chemists to understand matter at the molecular and nano levels. I view the primary mission of green chemistry as a mission to impart a sense of responsibility to chemists to manage matter safely. I would hope the GCI has brought more chemists at U of T and beyond to consider this responsibility, and I’m really encouraged by the bright, dedicated people who continue to lead the GCI forward.

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Greener Alternatives in Organic Synthesis Involving Carbonyl Groups: Dethioacetalization and Iron-Catalyzed Transfer Hydrogenation

By Diya Zhu, Member-at-Large for the GCI

A carbonyl functionality is a functional group composed of a carbon atom double-bonded to an oxygen atom (C=O). It is ubiquitous in nature as well as widely employed and studied in all areas of chemistry. In this blog, we will explore two common synthetic processes involving carbonyl groups with greener alternative reagents.

Dethioacetalization with NH4I

Carbonyl-containing compounds are abundant in nature, expressing a wide range of functionality. As targeted in many natural and non-natural product syntheses, the protection and deprotection of the carbonyl functional groups are critical and often require multiple steps. Common carbonyl protecting groups are dithianes and dithiolanes due to their easy accessibility and high stability under acidic/basic conditions. The traditional dethioacetalization is generally performed utilizing heavy-metal salts such as mercury(II) chloride, silver(II) nitrite, ceric ammonium nitrate, and selenium dioxide, of which the resulting waste is very toxic to the environment.1

From 1989 to 2005, serval hypervalent iodine compounds such as bis(trifluoroacetoxy)-iodobenzene (BTI), Dess-Martin periodinane (DMP), and o-iodoxybenzoic acid (IBX) have been employed as dethioacetalization reagents due to their low toxicity, high selectivity, and metal-ion free nature. While these reagents have a smaller environmental impact, they are still required in excess amount, which is economically wasteful.2, 3

Finally, in 2011, Ganguly and Mondal reported a mild, efficient, and greener dethioacetalization protocol using a catalytic amount of ammonium iodide with hydrogen peroxide.3 In this work, the deprotection was carried out with 10 mol% of nontoxic ammonium iodide and 30% hydrogen peroxide as the terminal oxidizer in an aqueous medium in the presence of sodium dodecylsulfate (SDS). This protocol (Figure 1) shows a high yield (>90%) deprotection of 1,3–dithianes and dithiolanes of activated aromatics and even deactivated and sterically encumbered substrates. The high tolerance, low environmental impact, mildness, operational simplicity, high throughput, and generality of the protocol make it an intriguing alternative.

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The greener dethioacetalization protocol by Ganguly and Mondal. [3]

Iron-catalyzed transfer hydrogenation with formic acid

Various catalyst systems for the reduction of carbonyl compounds have been established, such as Meerwein–Ponndorf–Verley (MPV) reduction.4 However, only a handful of protocols were reported for the transfer hydrogenation of aldehydes due to the difficulty in controlling the chemoselectivity in the process.

In these conversional protocols of transfer hydrogenation, many side-reactions (for example, aldol condensations) take place after deprotection by the base. The heavy-metal catalysts (such as rhodium, iridium, and ruthenium complexes) are expensive and often poisoned by the substrates, resulting in non-recyclable catalysts and many side-products. In addition, the hydrogenation of carbon-carbon double bonds (C=C) and aldehydes compete, resulting in poor chemoselectivity.5,6 Due to these drawbacks, there was a significant desire for more efficient and environmentally benign catalytic systems.

In the last decade, iron catalysts have received much attention due to their nontoxic, abundant, and inexpensive qualities. In 2013, Beller and his colleagues published an efficient iron-based catalyst system for the highly selective transfer hydrogenation of aldehydes under mild conditions.6 In this system, they suggested that iron-tetraphos complexes [(Fe(BF4)•6H2O and P(CH2CH2PPh2)3) are able to catalyze a wide range of substrates such as aromatic, aliphatic, and α,β-unsaturated aldehydes to the corresponding alcohols in excellent yields (>99%). Without the presence of a base, formic acid is used as a cheap, environmental friendly, and easy to handle hydrogen source. In addition, no significant amounts of side products were observed.

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The iron-catalyzed transfer hydrogenation with formic acid. [6]

In addition to these two examples, many chemical companies promote the idea of green chemistry and offer more green choices to reduce environmental impact without compromising the quality and efficacy of research.7

 

References:

  1. J. Corey, B. W. Erickson, Journal of Organic Chemistry 36 (1971), 3553; E. Vedejs, P. L. Fuches, Journal of Organic Chemistry 36 (1971), 366.
  2. S. Kirshnaveni, K. Surendra, Y. V. D. Nageswar, K. R. Rao, Synthesis 15 (2003), 2295. DOI: 10.1055/s-2003-41055
  3. C. Ganguly, P. Mondal, Synthetic Communications 41 (2011), 2374. DOI: 10.1080/00397911.2010.502995
  4. Gladiali, E. Alberico, Chemistry Society Reviews 35 (2006) 226. DOI: 10.1039/B513396C
  5. S. M. Samec, J.-E. Bäckvall, P. G. Andersson, P. Brandt, Chemistry Society Reviews 35 (2006), 237. DOI: 10.1039/b515269k
  6. Wienhöfer, F. A. Westerhaus, K. Junge, M. Beller, Journal of Organometallic Chemistry 744 (2013) 156. DOI: 10.1016/j.jorganchem.2013.06.010
  7. Sigma Aldrich Alternative Product Page. http://www.sigmaaldrich.com/chemistry/chemistry-products.html?TablePage=119262253 (accessed Oct 15, 2017).

GCI gets behind-the-scenes look at GreenCentre Canada

by Dan Haves, Communications Officer, Department of Chemistry at U of T

This summer, the Green Chemistry Initiative (GCI) at U of T’s Department of Chemistry made a visit to GreenCentre Canada. The group of nine graduate students were in Kingston for a crash course on the transition from academia to industry in green chemistry. They learned from experts in the field on everything from product development to patents and intellectual property. We spoke with PhD student and GCI member Julia Bayne about the day.

What was the rationale behind organizing this career day?

Most graduate students are unfamiliar with green chemistry and tend to be unaware of potential careers for chemists other than academia or research positions in industry. Additionally, most students find it difficult to make the connection between academia and industry and this transition tends to cause a lot of people anxiety given their unfamiliarity with the latter. With this in mind, we, the Green Chemistry Initiative at U of T, wanted to plan a career day that would give students the opportunity to learn about other possible career options and to see the inner-workings of a successful company, whose mandate is built around green chemistry principles and sustainability.

Can you share a little bit of what you learned about GreenCentre and the work they do?

GreenCentre Canada is a one-stop shop for the commercialization of green chemistry technologies. They have a very hands-on approach to technology development and support the creation and development of green chemistry-based companies. They work with academics and entrepreneurs to commercialize their discoveries. As well, they provide support for established companies and help further develop research and development. They have a very diverse group of employees: experienced chemists, commercial experts and business professionals. Their unique skill set and talent has allowed them to develop new green chemistry-based technologies, support existing ones and create small businesses.

GCI Visit group photo

Were there any take-aways from the day in terms of potential career paths you may not have known about or some that you learned more about?

I think most people believe that in order to pursue a career outside of your field of study that you need to go back to school, which for graduate students who have been in school for at least ten years, can be intimidating. However, one thing that stood out to me from the visit was that you don’t necessarily have to have a degree or years of experience in a field outside of chemistry to hold a position that requires less chemistry. For instance, with a chemistry background, starting in a research position will definitely help develop your skills as a scientist, but this does not mean you can only be a research scientist. We learned that if you apply yourself, if you ask for additional responsibilities, if you teach yourself about another field you’re interested in, you can prepare yourself to change positions/careers and move away from a laboratory position – if you want. We learned that our chemistry degrees are valuable, not only for researcher positions, but also for leadership roles and business development roles. For most chemistry graduate students, these positions may seem unattainable with only research experience in your niche field. However, I found it interesting and encouraging to learn that the main separator is on-the-job-training and the passion and willingness to learn. Moreover, I learned that careers outside of the laboratory – like management or business development roles – are not outside of our reach as chemists!

What excites you the most about where you see green chemistry going?

Green chemistry has been receiving an increasing amount of attention in the recent years and most people now understand and appreciate that green chemistry has the potential to change our world for the better by developing sustainable, prosperous and healthy communities. With an overwhelming increase in population and decrease in resources predicted for our future, we need everyone to be thinking about green chemistry and sustainability. We’ve seen green chemistry practices used throughout U of T and we have seen first-hand the benefits associated with these changes, including energy and cost savings and a smaller environmental footprint. And I hope this continues!

I am looking forward to seeing these practices being implemented more at the university level throughout Canada and then at the federal level. Being the first school in Canada to sign the Green Chemistry Commitment, U of T has taken a pledge to implement green chemistry principles and practices into the undergraduate and graduate curriculum, and I hope this becomes the standard for all universities. I’m excited to see all levels of academia, industry and government working together to implement more green chemistry into our society, I’m excited to see how green chemistry will impact our lives and I am looking forward to what the future will look like!

Julia is a 4th-year PhD student working in the Stephan Research Group. Her research is focused on the design of new phosphorous-based compounds for Lewis-acid catalysis and frustrated Lewis pair reactivity.

 

This article was reproduced from the Department of Chemistry in the University of Toronto, see the original article here.

Ecocatalysis: Harnessing Phytoextraction for Chemical Transformations

Ecocatalysis: Harnessing Phytoextraction for Chemical Transformations

By Karlee Bamford, Treasurer for the GCI

What is ecocatalysis? I had never heard this term before until reading a recent publication from Grison and coworkers in the RSC journal Green Chemistry entitled “Ecocatalyzed Suzuki cross coupling of heteroaryl compounds”.1 In this work, the authors perform the familiar Suzuki cross-coupling of arylboronic acids (Figure 1) with heteroaryl halides. However, they use a thoroughly unfamiliar palladium catalyst: the common water hyacinth (Figure 2).

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Figure 1. The general reaction for Suzuki cross-coupling  (Ar = substituted phenyl, thiophene, or indole groups).

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Figure 2. The common water hyacinth (Eichhornia crassipes). Credit: Richard A. Howard, provided by Smithsonian Institution, Richard A. Howard Photograph Collection (Montréal, Canada). [2]

In broad terms, ecocatalysis is the use of plant-derived, metal-based catalysts in chemical reactions. If it were not for the author’s graphical abstract illustrating the plant body performing catalysis, I would have assumed that this was a more standard bioinorganic paper featuring a plant extract as catalyst. While the propensity of certain plants and microbiota to uptake (“phytoextract”) particular contaminants has long been used in waste water purification, for example in the uptake of inorganic phosphates (e.g. [PO4]3-),3 ecocatalysis represents a clever progression from plants being used in chemical sequestration to chemical transformation.

Plants currently used in phytoremediation, that is, the removal of contaminants such as heavy metals from anthropogenically polluted environments, could clearly be used in the production of ecocatalysts.4 One current use for such metal-laden plants is in phytomining as so-called bio-ore.5 This metal extraction process ultimately results in the majority of the plant bio-mass being wasted through the energy-consumptive process of incineration, whereas an ecocatalyst such as EcoPd requires that same bio-mass as a kind of ligand support.

Grison and colleagues report reaction times, conditions, and yields (typically >90 %) for their “EcoPd” catalyst that are competitive with typical Suzuki cross coupling experiments and catalysts, both homogenous and heterogeneous. Remarkably, the primarily root-based EcoPd catalyst can be reclaimed and reused without loss of activity, as the authors demonstrated in a control study that involved recycling the catalyst four times over. Finally, the palladium content of the used catalyst can be quantitatively recovered by rhizofiltration, that is, by returning the elemental palladium obtained in post-synthesis work-up to a new plant specimen for metal uptake. In practical terms, this involves filtering the post-synthesis solution, dissolving the isolated solids with aqua regia, and diluting the resultant palladium-containing solution with water before reintroducing it to the roots of E. crassipes.

Ecocatalysis is an entirely new and emerging field of chemistry (circa 2013) being pioneered by Grison and coworkers at The Laboratory of Bio-inspired Chemistry and Ecological Innovations (University of Monpellier) in France. Their research has furnished several other noteworthy ecocatalysts (EcoM’s) featuring nickel (EcoNi),6 zinc (EcoZn),7 manganese (EcoMn),8 copper (EcoCu),9 which have proven effective in Biginelli, Diels-Alder, reductive amination, and Ullmann reactions, respectively.

This new approach to catalysis is not only charmingly novel – at least to a non-bioinorganically-minded chemist such as myself – but it also offers a real solution to the problematic dependence of catalysis on pure precious metals. The plants themselves provide a means for both harvesting and using low-abundance metals in a format that does not require complicated ligand design and is consistent with homogenous catalysis. Clearly, EcoPd and other such EcoM may not be suitable replacements in every metal-catalyzed transformation, but they nonetheless provide a new avenue for recycling precious metals and realising catalyst sustainability.

The range of possible ecocatalysts is, in my mind, astounding. Plant species that are known to preferentially accumulate heavy metals, known as accumulators and hyperaccumulators, are greater than 500 in number and sequester metals from across the p- and d-block of the periodic table, each to varying extents.10 As the tolerance and preference for certain transition metals is in part gene-regulated,11 it is conceivable that genetic modification and controlled environmental conditions could in the future yield heavy metal-specific plant species for sequestration and, perhaps, subsequent ecocatalysis.

 

References:

  1. G. Clavé, F. Pelissier, S. Campidelli and C. Grison, Green Chemistry, 2017, DOI: 10.1039/c7gc01672g.
  2. Used with permission from Larry Allain, hosted by the USDA-NRCS PLANTS Database.
  3. J. Lv, J. Feng, Q. Liu and S. Xie, Int. J. Mol. Sci., 2017, 18.
  4. C. Grison, Environmental Science and Pollution Research, 2015, 22, 5589-5591.
  5. R. R. Brooks, M. F. Chambers, L. J. Nicks and B. H. Robinson, Trends in Plant Science, 1998, 3, 359-362.
  6. C. Grison, V. Escande, E. Petit, L. Garoux, C. Boulanger and C. Grison, RSC Adv., 2013, 3, 22340.
  7. V. Escande, T. K. Olszewski and C. Grison, Comptes Rendus Chimie, 2014, 17, 731-737.
  8. V. Escande, A. Velati, C. Garel, B.-L. Renard, E. Petit and C. Grison, Green Chemistry, 2015, 17, 2188-2199.
  9. G. Clavé, C. Garel, C. Poullain, B.-L. Renard, T. K. Olszewski, B. Lange, M. Shutcha, M.-P. Faucon and C. Grison, RSC Adv., 2016, 6, 59550-59564.
  10. H. Sarma, Journal of Environmental Science and Technology, 2011, 4 118-138.
  11. S. Jan and J. A. Parray, Approaches to Heavy Metal Tolerance in Plants, Springer Singapore, Singapore, 2016.
ACS Summer School on Green Chemistry and Sustainable Energy 2017

ACS Summer School on Green Chemistry and Sustainable Energy 2017

By Samantha Smith, Yuchan Dong, and Shira Joudan

Yuchan Dong, who previously studied in China, had begun to miss life with roommates while in Canada. She reminisced about how you could talk about your lives late into the night, and spend meals chatting with friends in the cafeteria. “Luckily, at the ACS summer school, [she] got the chance to experience such life again and got to know a lot people who share same interests.” The summer school brought us back to the more carefree times of our undergraduate lives. Living in dormitories, sharing a floor with fifty-two other highly educated students, sharing every meal with our newly-formed friends, and even tackling homework assignments were just like the “good old days”. The level of diversity strengthened the value of peer-networking and real friendships were made throughout the week.

ACS Summer School blog1

The week wasn’t just filled with relaxing chats in the Colorado sun; that was merely how we spent our free time. The days were jam-packed with riveting lectures during the day, assignments in the evening, and getting to know the local Golden beers at night (which was obviously a duty of ours as tourists). We also had the chance to take in the local scenery with hikes and whitewater rafting.

The ACS summer school on green chemistry is a competitive program offered to graduate students, post-doctoral fellows, and industry members every year in Golden, Colorado. Hosted by the Colorado School of Mines, the program consists of five days of lectures from green chemistry and sustainable energy experts, two poster sessions, a whitewater rafting trip, and lots of opportunity for networking. This program teaches global sustainability challenges with a focus on sustainable energy. The ACS Summer School is free of charge for successful attendees, including travel, accommodation on campus, and meals.

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Samantha, Yuchan, and Shira at the ACS Summer School

Jim Hutchison, a professor at the University of Oregon, spoke about how his department has completely reformatted their undergraduate chemistry curriculum to contain green and sustainable chemistry, something that particularly sparked Shira’s interest as lead of GCI’s Education Subcommittee. Bill Tolman, Chair of the University of Minnesota Chemistry Department, shared how students successfully cultivated the safety culture within his department. This had inspired Samantha to create new initiatives within our chemistry department. Queens University’s Professor Philip Jessop taught us about Life-Cycle Analysis (LCA) and assigned us multiple processes for which we calculated the gate-to-gate LCA. Mary Kirchhoff and David Constable from ACS gave talks on green chemistry and ACS resources, many of which would be useful to other departments. The format of the summer school allowed plenty of time to chat with the guest lecturers during coffee breaks, lunches, and poster sessions.

Many real-world issues were discussed. The worldwide energy usage and sources of energy were a main topic of discussion, as was the use of alternative sources. We were blown away by how multi-disciplinary green chemistry is, and we were enlightened on how we need experts in all fields to successfully create sustainable chemistry. We learned that to be able to effectively tackle environmental issues we need great synthetic chemists, whether they specialize in organic, materials or catalysis, as well as analytical chemists, engineers, environmental chemists, and toxicologists. We also need effective entrepreneurs and lobbyists.

Nearing the end of the summer school, a large group of us hiked up Tabletop mountain to get the most amazing view of the valley. A warm feeling of appreciation towards the summer school for bringing us out of the isolation of individual research in the busy city life was shared. We would like to thank ACS for giving us the chance to attend this amazing week. This experience has truly been beneficial to us, and we plan to use the knowledge gained during the week in our own studies as well as pass this knowledge on to our coworkers at the University of Toronto.

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Tabletop mountain in Golden, CO

We highly encourage anyone interested in green chemistry and sustainability to attend this beneficial program. Application deadlines are early in the year and submitted online. The application consists of the applicant’s CV, unofficial transcript, letter of nomination from faculty advisor or another faculty member, and a one-page essay describing your interest in green chemistry and sustainability as well as how it will benefit the applicant.

Green Chemistry Principle #9: Catalysis

By Alex Waked, Member-At-Large for the GCI

9. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.

In Video #9, Lilin and Jamy discuss the advantages of catalytic reagents over stoichiometric reagents.


In stoichiometric reactions, the reaction can often be very slow, may require significant energy input in the form of heat, or may produce unwanted byproducts that could be harmful to the environment or cost lots of money to dispose of. Most chemical processes employing catalysts are able to bypass these drawbacks.

A catalyst is a reagent that participates in a chemical reaction, yet remains unchanged after the reaction is complete. The way they typically work is by lowering the energy barrier of a given reaction by interacting with specific locations on the reactants, as demonstrated in Figure 1 below. The reactants are represented by the red and blue objects, and the catalyst by the green one. Without catalyst, the reactants cannot react with each another to form the desired product. However, once the catalyst interacts with them, the reactants become compatible and can subsequently react together. The desired product is released and the catalyst is regenerated to continue interacting with the remaining reactants to produce more product.

Principle 9 Figure 1 - catalysis

Figure 1. Graphic of a catalyst’s function in a catalytic reaction. The catalyst is green, and the reactants are red and blue.

In other words, a catalyst can be thought of as a key that can unlock specific keyholes, where a keyhole represents a particular chemical reaction. One common example of a catalytic reaction that is taught in introductory organic chemistry is the hydrogenation of ketones (Scheme 1, also discussed in the video). The stoichiometric reaction involves the addition of sodium borohydride, followed by addition of water. In this reaction, borane (BH3) and sodium hydroxide are (formally) generated as waste. By simply employing palladium on carbon as catalyst, the ketone can react directly with H2 to generate the same desired product without producing any waste.

Principle 9 Scheme 1 - catalysis example

Scheme 1. Stoichiometric vs. catalytic reduction of a ketone.

While catalytic reagents appear to play an impactful role in the development of greener processes, there are always a couple points on the flip side of the coin to consider. For instance, a reaction employing a catalyst may not necessarily be “green”, since the “greenness” of the catalyst itself should be considered as well (ie. Is the catalyst itself toxic? Is it environmentally benign?). In addition, the lifetime of a catalyst matters; a catalyst can in theory perform a reaction an infinite number of times, but in practice it loses its effectiveness after a certain period of time.

Nevertheless, when these points are considered and addressed, the impact of catalytic reagents on green processes cannot be ignored. The production of fine chemicals and the pharmaceutical industries are just a couple areas where this impact is seen.[1] By focusing innovative research around the principle of catalysis, together with the other principles of Green Chemistry, we are moving in the right direction by paving the way to new sustainable processes.

Reference:
[1] Delidovich, I.; Palkovits, R. Green Chem. 2016, 18, 590-593.

A New Green Chemistry Metric: The Green Aspiration Level™

A New Green Chemistry Metric: The Green Aspiration Level™

By Samantha A. M. Smith, Member-at-Large for the GCI

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Figure 1. Process materials – green mass metric relationships

Green Chemistry Principle number two, Atom Economy, focuses on metrics used to compare the efficiency of a reaction.1 However, Atom Economy doesn’t take into account solvents, reagents such as catalysts, drying agents, energy, or recyclability of any of the materials. Is it reasonable for an industry such as pharma to use such a metric? What about E-factor, which is a measure of process waste and, if “complete” (cEF = complete E-factor), also recyclability of solvents and catalysts? It’s known that the pharmaceutical industry generally has the highest E-factor values compared to petrochemicals, bulk, and fine chemicals, indicating more waste generated per mass of desired product.2 But if you wanted to compare your technology to already implemented pharmaceutical processes, where would you find such information?

Roschangar, Sheldon, and Senanayake created a new metric for such a purpose: the Green Aspiration Level™.3,4 This new metric allows one to compare an ideal process with the average commercial process in terms of environmental impact for the production of a pharmaceutical. Say you have an alternative product to Viagra™ and want to know if its production is more or less impactful. You could apply any of the existing metrics (including yield, atom economy, E-factor, and more, summarized in Table 1 of reference 3), or you could use the Green Aspiration Level™ (GAL). To do so, you determine the waste (Complete Environmental Impact Factor (cEF) or Process Mass Intensity (PMI)) and assess the complexity of the process, and use those to calculate the GAL, and in turn the Relative Process Greenness (RPG). From there, you can consult Table 1 (below) to determine the greenness rating of such a process.4

Waste and Complexity

Waste refers to a simple metric such as cEF or PMI (with reactor cleaning and solvent recycling excluded). Complexity of the process refers to the number of steps with no concession transformations, that is those that do not directly contribute to the building of the target molecules’ skeleton.5 The waste and complexity metrics require that the process starting materials are less than $100 USD/mol for proper comparison.

Green Aspiration Level™

Roschangar and coworkers have collected data on many commercial processes to develop an appropriate metric, and they currently use 26 kg of waste per kg of product as a standard based on their findings. This value is known as the average GAL, or tGAL.3,4

GAL        = (tGAL) x Complexity

= 26 x Complexity

Relative Process Greenness

RPG       = GAL/cEF

This metric is used as the comparison point for processes. The comparison can be done at different stages of development, either early or late development, and then again for those processes that are commercialized. In Table 1, there are minimum RPG values that will associate the process with an appropriate greenness percentile.

RPI         = RPG(current) – RPG(early)

RPG can also be used to determine the improvement of a process. From early development, to late development, to commercialization, the difference in consecutive RPG values will give your Relative (Green) Process Improvement (RPI). In this case, the higher the number the better.

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Table 1. Rating Matrix for Relative Process Greenness (RPG) in Pharmaceutical Drug Manufacturing [3]

It turns out the current commercial process for Viagra™ is actually quite efficient and is currently in the 90th percentile, exceeding the commercial average by 143% (RPG). The full process of determining and using this new metric, the Green Aspiration Level™, is described by Roschangar and coworkers in two very in-depth articles.3,4

References

1 Anastas, P. T., Warner, J. C. “Principles of green chemistry.” Green chemistry: Theory and practice (1998): 29-56.

2 Sheldon, R. A., Catalysis and Pollution Prevention, Chem. Ind. (London), 1997, 12–15.

3 Roschangar, F., Sheldon, R. A., Senanayake, C. H., Green Chem. 2015, 17, 752. DOI: 10.1039/C4GC01563K

4 Roschangar, F., Colberg, J., Dunn, P. J., Gallou, F., Hayler, J. D., Koenig, S. G., Kopach, M. E., Leahy, D. K., Mergelsberg, I., Tucker, J. L., Sheldon, R. A., Senanayake, C. H., Green Chem. 2017, 19, 281. DOI: 10.1039/c6gc02901a 

5 Crow, J. M., “Stepping toward ideality”, Chemistry World, accessed July 13th, 2017. URL: https://www.chemistryworld.com/feature/stepping-toward-ideality/5190.article

Figures from Roschangar et al. 2015 reproduced with the permission of the Royal Society of Chemistry.