Water Extract of Banana: The Tasty Fruit for Efficient Green Chemistry

Water Extract of Banana: The Tasty Fruit for Efficient Green Chemistry

By Matt Gradiski, Member-at-Large for the GCI

Bananas. They’re a fantastic healthy snack, delicious to bake into bread or flavour medicine, and even the choice speak-and-spell for singer Gwen Stefani. Now, thanks to two excellent reports in 2015, an efficient medium for two sophisticated organic transformations can be added to its list of uses.

Published in Green Chemistry in January 2015, researchers were able to perform Suzuki-Miyaura (SM) cross-coupling in a neat solution of water extract of banana (WEB).1 WEB is made by simply drying the peel of a banana, burning the dried remains, and extracting the ashes with water (Figure 1). What results is a brown-orange liquid holding tremendous catalytic capability.

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Figure 1. Preparation of WEB solution [1]

 Typically, SM coupling requires the addition of external ligands, base, or other reaction promoters that can often be very expensive. The reaction is known to be able to take place in aqueous media; however, organic solvents are usually the more common choice. While the SM reaction still requires a noble-metal palladium catalyst, using a WEB medium for this reaction completely replaces the use of external additives and organic solvents (Figure 2). The only thing better than being able to do your reaction in water, is to do your reaction in water quickly! The longest reported reaction time using this system was 20 minutes, with times as a low as 5 minutes, and yields as high as 99%, all being carried out at room temperature for 12 different products.

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Figure 2. Example of Suzuki-Miyaura coupling in WEB

Extending the scope of WEB’s usefulness, a report in July of the same year in Green Chemistry showed that the medium can also be used effectively for the catalytic Dakin reaction.2 This reaction converts an ortho- or para-hydroxy aromatic aldehyde or ketone into its corresponding benzenediol through reaction with hydrogen peroxide in base (Figure 3).

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Figure 3. Proposed Dakin oxidation mechanism catalyzed by WEB [2]

Similar to SM coupling, the Dakin reaction requires addition of an external base, typically sodium or potassium hydroxide. However, it was found in the study that no external base was required when the reaction was carried out in WEB. The WEB solution was effective enough to initiate the reaction via deprotonation of hydrogen peroxide, generating the nucleophilic hydroperoxide anion that is required for the reaction to take place. All 16 reactions screened in the study were carried out at room temperature with the use of no external additives or organic solvent. Reaction times were as long as 60 minutes, and isolated yields ranged from 90-98%!

But what makes WEB such an efficient medium for green chemistry? Although the exact identity of the active species is currently unknown, the two aforementioned studies gathered valuable information about what could be promoting their reactions from a report in 2007.3 It was identified that banana peels contain a large amount of potassium and sodium carbonate as well as sodium chloride and other trace elements. It was speculated that the high concentration of alkali metal carbonates in WEB was responsible for the acceleration of these organic transformations.

So, the next time you are finished having a banana, don’t monkey around and throw it away! Give it to a chemist in need, it may help them out more than you think!

 

References

1)         P. R. Boruah, A. A. Ali, B. Saikia and D. Sarma, Green Chem., 2015, 17, 1442–1445. DOI:10.1039/C4GC02522A

2)         B. Saikia, P. Borah and N. Chandra Barua, Green Chem., 2015, 17, 4533–4536. DOI:10.1039/C5GC01404B

3)         D. C. Deka and N. N. Talukdar, IJTK, 2007, 6 (1), 72-78.

 

Figures from Boruah et al. 2015 and Saikia et al. 2015 reproduced with the permission of the Royal Society of Chemistry.

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Veggie (Scrap) Tales – Are plant-based polymers the answer to our plastic conundrum?

By Molly Sung, Secretary for the GCI

Plastic is one of the most ubiquitous materials on the planet. Everything from our toothbrushes, to pens, take-out containers, or parts used in the automotive or aeronautic industries are made from plastic. What started off as a convenient and cheap alternative to traditional materials has become a global reliance – and it’s taking its toll.

Traditional plastics are petroleum-based – and as we know, petroleum is a non-renewable resource and its extraction, processing, and use contributes to environmental pollution and climate change. When plastic bags were first gaining popularity in the 1950s and 60s, one of the selling points of using plastic bags was that they were more durable and long-lasting than paper,1 but that’s also exactly the problem. Plastic doesn’t degrade easily like paper does, so it starts to accumulate. This accumulation in landfills and, unfortunately, our waters has spurred research in the development of plastics that can break down over time.

An example of a biodegradable plastic is polylactic acid (PLA). The starting material, lactic acid, can be obtained through fermentation of crops such as sugarcane or corn, which can undergo condensation to form short chains (oligomers). Next, these oligomers undergo depolymerization to form lactide, a cyclic ester, which is then polymerized with the help of a catalyst to give PLA, shown in Figure 1.2

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Figure 1. Synthesis of polylactic acid (PLA), a biodegradable plastic, from lactic acid.

PLA performs comparably to the popular commercial plastic polyethylene terephthalate (PET, labelled with the “1” inside the recycling symbol). It is currently used in food packaging (such as disposable cups), as medical implants,2 and has also found renewed popularity as a common filament for 3D printing, but it’s not without its problems. The monomer, lactide, can have varying stereochemistry which influences the final polymer product and the mechanical properties of the plastic. Significant strides have been made in this area of research, but possibly the biggest barrier to using PLA is the competition with the food industry for the starting material. This is incidentally the same problem many first-generation biofuels ran into. But what if we could take food waste and turn it into usable plastics?

While there are some technologies being developed to use non-food materials like cellulose as a bioplastic, many of these methods require fairly harsh reactions. A gentler, water-based approach to make a cellulose-based plastic was recently reported by a research team from the Italian Institute of Technology and the University of Milano-Bicocca in the journal Green Chemistry.3

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Figure 2. Image of the bioplastic films made from different vegetable powders: (A) carrot, (B) parsley, (C) radicchio, (D) cauliflower. Reproduced from Perotto et al. [3].

This new technique uses waste from the food-industry, including carrot, cauliflower, radicchio, or parsley waste. The vegetable matter must first be dried and ground into a micronized powder, but otherwise no further processing or purification is required to make the veggie waste usable in this process. To make the plastic films, the researchers simply mixed the vegetable powder with a weakly acidic solution (5 % HCl w/w) at 40 °C, then removed any residual acid through dialysis and let the suspension dry in a petri dish for 48 hours. This process has a 90 % conversion of the vegetable waste into bioplastic (by weight) and the product has very promising mechanical properties (Figure 2).

In particular, in measuring the elasticity and tensile strength of the bioplastic films, it was found that the carrot film had comparable properties to polypropylene (commonly used for rigid plastic containers – otherwise referred to as number “5” plastics).

The researchers also tested important factors for plastics being considered for food storage applications. First, they studied whether the films would interact with water. The parsley film was found to absorb water fairly readily. Conversely, the carrot filmed exhibited hydrophobic behaviour – an uncommon characteristic for vegetable-derived plastics. This hydrophobic behaviour means that the moisture from food is unlikely to soak through the plastic film or structurally damage it.

One very interesting property of the radicchio waste is that it is rich in anthocyanins. Anthocyanin is what gives radicchio, red cabbage, and beets their vibrant red colour. More importantly, anthocyanins are known anti-oxidants and materials rich in these anti-oxidants are currently being investigated as food-packaging materials that extend the shelf-life of food.4 Unfortunately, these vegetable films tested to be fairly permeable to oxygen, which would offset any benefit from the antioxidant-rich radicchio film. However, the researchers showed that if the vegetable waste was blended with polyvinyl alcohol (PVA), the oxygen permeability can be reduced significantly and was even an improvement on the pure PVA.

Lastly, and very importantly, the researchers tested for the biodegradability of the films. To test the rate of biodegradation, the researchers submerged the carrot film in seawater to measure the rate of oxygen consumption by the seawater organisms responsible for the biodegradation of the film. They found that the film decomposed fairly quickly in 15 days.

These scientists have now demonstrated a very mild process in the synthesis of bioplastics that have mechanical properties similar to one of the most common commercial plastics. They have also made a plastic that, because of the presence of anthocyanins, may have applications in food storage that can help reduce food-waste.

What is especially promising about these bioplastics is how little purification of the vegetable waste is required to make them; however, there are improvements to be made. A major obstacle these materials will face is their performance in wet or humid environments as well as scaling up to an industrial process. It is clear that we need more sustainable materials and these vegetable waste plastics present an exciting new avenue towards biodegradable bioplastics.

 

References

  1. Laskow. How the Plastic Bag Became So Popular. The Atlantic [Online] 2014. https://www.theatlantic.com/technology/archive/2014/10/how-the-plastic-bag-became-so-popular/381065
  2. Gupta et al., J. Prog. Polym. Sci. 2007, 32, 4, 455-482. DOI: 10.1016/j.progpolymsci.2007.01.005
  3. Perotto et al., Green Chemistry, 2018, 20, 804-902. DOI: 10.1039/C7GC03368K
  4. N. Tran, et al., Food Chemistry, 2017, 216, 324-333. DOI: 10.1016/j.foodchem.2016.08.055

 

Figure from Perotto et al. 2018 reproduced with the permission of the Royal Society of Chemistry.

Glycoside Hydrolases: A Doorway to Alternative Energy

Glycoside Hydrolases: A Doorway to Alternative Energy

By Namrata Jain, GreenChem UBC (Invited post!)

Biofuels, in particular bioethanol, are widely accepted as carbon-neutral fuels1, meaning they have no net greenhouse gas emissions; the amount of carbon dioxide produced during their combustion equals the amount fixed from the atmosphere while the plants grow. These fuels provide an alternative to the current outrageous usage rate of fossil fuels. Plant biomass, a renewable and abundantly available natural resource, is used as the main source for bioethanol production.

In order to produce bioethanol, polymeric plant carbohydrates (polysaccharides) must be broken down into the corresponding monosaccharides, followed by fermentation via yeasts. Typically, starch-rich crops such as corn and sugarcane are the most heavily used as carbohydrate sources.

However, since utilization of these starchy sugars in bioethanol production competes with their use as food crops, there has been a recent shift towards utilization of lignocellulosic biomass.1 Lignocellulosic biomass includes cellulose and hemicelluloses present in non-edible parts of plants, and hence reduces dependence on edible, starch-rich crops.

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Figure 1. Structure of a plant cell wall, highlighting xyloglucan, a particular hemicellulose of interest. [2]

Lignocelluloses form an important part of the plant cell wall (Figure 1) and are composed of cellulose, hemicelluloses (such as xyloglucan), and polyaromatics called lignin. These polymers are tough and more difficult to break down to release monosaccharides, as compared to starch. Nevertheless, lignocelluloses are the most abundant biological material on earth and are an untapped resource.1

The complete utilization of this biomass, however, is hindered by the structural complexity of plant cell walls, arising from the heavy crosslinking between hemicelluloses, celluloses, and lignin within, making it difficult to access the degradable polysaccharidic components. Hemicelluloses, such as xyloglucan (Figure 2A), can make up 15-50 % of these lignocellulosic materials and have been the focus of research for optimization to use as a biofuel.

To efficiently break down the lignocelluloses, many types of enzymes are needed. Glycoside hydrolases, one such group of carbohydrate active enzymes, have proven to be very efficient in the hydrolysis of many complex polysaccharides.3 However, more details about the chemical structure of the enzymes, as well as a reliable way of comparing the kinetic activity of various enzymes has been of interest to researchers in the field.

One of the ways of quantifying the kinetic details of such enzymes is by designing chemical probes such as one shown in Figure 2B. Such probes are chemically very similar in structure to the polysaccharide of interest (eg. Figure 2A), and hence can subtly fit into the active site of the enzyme and manipulate its rate of catalysis in a controlled and quantifiable way, making comparisons between enzymes’ kinetics possible.

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Figure 2. Structures of (A) xyloglucan; and (B) xyloglucan oligosaccharide based probe.

These probes can also assist in the crystal structure formation of the enzyme providing key details about the nature of interactions between the enzyme and corresponding polysaccharide and the specific amino acids responsible for its catalytic activities (Figure 3).

The Brumer group at the University of British Columbia4 has recently designed one such probe (Figure 2B) specific for xyloglucan active enzymes (xyloglucanases) by chemically modifying a xyloglucan-derived heptasaccharide. This probe was able to provide valuable information about the kinetics, specificity, as well as structural details of a newly discovered xyloglucanase PbGH5, which is secreted by a microbe residing in the intestinal system of ruminants such as cows.

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Figure 3. Crystal structure of the characterised endoxyloglucanase in complex with the inhibitor. [4]

As more research goes into the design and improvement of such probes, we would be able to develop novel enzyme cocktails that can make bioethanol production more economically and practically viable, leading to gradual decrease in our dependence on fossil fuels for our energy needs.

 

References:

  1. Scheffran J. The Global Demand for Biofuels: Technologies, Markets and Policies. In: Biomass to Biofuels: Strategies for Global Industries. Blackwell Publishing Ltd.; 2010:27-54. doi:10.1002/9780470750025.ch2.
  2. https://en.wikipedia.org/wiki/Cell_wall#Plant_cell_walls
  3. Henrissat B, Davies G. Structural and sequence-based classification of glycoside hydrolases. Curr Opin Struct Biol. 1997;7(5):637-644. doi:http://dx.doi.org/10.1016/S0959-440X(97)80072-3.
  4. McGregor N, Morar M, Fenger TH, et al. Structure-function analysis of a mixed-linkage β-glucanase/xyloglucanase from key ruminal Bacteroidetes Prevotella bryantii B14. J Biol Chem. 2015;291(3):1175-1197. doi:10.1074/jbc.M115.691659.

Green Chemistry Principle #10: Design for Degradation

By Shira Joudan, Chair of the Education Subcommittee for the GCI

10. Design for degradation: Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.

In video #10, Matt and I discuss designing chemicals that break down once their desired function is completed. Essentially, we want chemicals to degrade to molecules that are not harmful to humans, animals or the environment.

A lot of the chemicals we use in our day-to-day lives need to be stable to perform their function. For example, if your coffee mug dissolved when you poured your coffee into it, it wouldn’t be very helpful! Similarly, if lubricants degraded under high temperature and pressure, they may not work well in the engines of our cars or planes.

Once chemicals are done providing their main function, they might end up in a landfill or wastewater treatment plant where they can enter the waters, soil and air of our environment, or be taken up by animals or humans. The biggest challenge is making chemicals that are stable during usage, but don’t persist in the environment – or in other words, chemicals that can be degraded. Another important thing – we want the breakdown products to also be non-toxic and not persistent! It’s important to remember that there are different reasons a chemical can break down. It can be due to reactions with light (photodegradation), water (hydrolysis) or biological species, often with enzymes (biodegradation).

A common example that we hear about is biodegradation, especially with the well-known “biodegradable soaps.” We can use this as a good example about how we can design soaps, or detergents, to break down more easily in the environment.

Sodium dodecylbenzenesulfonate

Figure 1 Sodium dodecylbenzenesulfonate, an example of a linear alkylbenzene sulfonate (LAS) which is biodegradable.

Sodium dodecylbenzenesulfonate (Figure 1) is a common detergent, and is often referred to as LAS, for linear alkylbenzene sulfonates. Looking at its structure, you can see that it has a linear alkyl chain with a benzylsulfonate attached to it. It is useful as a detergent because it has a polar headgroup (sulfonate) and a non-polar alkyl group, making it a surfactant.

LAS is used in many things, especially laundry detergent. It degrades quickly in the environment under aerobic conditions, or when oxygen is present, because microbes are able to use to the linear alkyl chain as energy, via a process called β-oxidation, a process which breaks down the carbon chain. Once the long chain is degraded, the rest of the molecule can be degraded as well.

Branched alkylbenzene sulfonate.

Figure 2 A branched alkylbenezene sulfonate (does not biodegrade).

If you compare LAS to a branched version (Figure 2), you can immediately see that the alkyl chain looks very different. This molecule was also used as a detergent just like the linear version, but because of the location of the branches, microbes cannot perform β-oxidation since there are no good sites for that reaction to be initiated. Therefore, these branched detergents have been phased out in most developed countries because they are too persistent – they do not biodegrade.

The main way these molecules are degraded is through microbes, when oxygen is present. So if these soaps end up directly in water, like straight into a lake, they will not be broken down very quickly (even the linear version!). This is because there are fewer microbes in water as compared to in soil. Interestingly, the branched version is 4 times less toxic than the linear version, but can cause more damage because of its persistence. This is one of the reasons that it is very important to consider persistence, or a molecule’s resistance against degradation, and not only its toxicity.

You can see how designing chemicals to break down can be very challenging, but many researchers around the world are working on this right now. Some examples are biodegradable polymers that are used in plastics, like compostable cutlery.

Principle 10 is currently one of the largest challenges in green chemistry. If scientist designing new chemicals understand more about the mechanisms that can degrade them, we may be able to make chemicals that are reliable and stable during their intended use, but break down in the environment!

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.

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.