Green Chemistry Principle #8: Reduce Derivatives

By Trevor Janes, Member-at-Large for the GCI

8. Unnecessary derivatization (e.g. installation/removal of use protecting groups) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.

In Video #8, Cynthia and Devon look at one common example of derivatization, which is the use of protecting groups in chemical reactions. To help illustrate the concept of a protecting group, they use toy building blocks.

In this blog post, I will use cartoons such as the one shown below (a specific example of the use of protecting groups will be shown at the end of this post).

Principle 8 - unselective reaction

Figure 1 An unselective reaction.

In Figure 1, the starting material contains two reactive sites, represented by U-shaped slots. We only want the slot on the right to react with the reagent, shown as red circles. The starting material is reacted with the reagent in order to make the desired product, but an undesired product also forms, because both U-shaped slots react with the red circle. In other words, Figure 1 shows an unselective reaction because a mixture of products is made.

Formation of the undesired product can be avoided by carrying out a protection reaction before using the red reagent, and then carrying out a final deprotection reaction. This sequence of reactions is shown in Figure 2.

Principle 8 - selectivity through protecting groups

Figure 2 A selective reaction through the use of a protecting group, which temporarily blocks the reactive site on the left side. 

 

Figure 2 shows how a selective reaction is traditionally done – through the use of a temporary block, known as a protecting group. The starting material can be protected by blocking one of the reactive sites, represented by the blue rectangle covering the U-shaped slot on the left. This intermediate only has one reactive site left, so the second reaction with the red reagent can only happen at the empty U-shaped slot on the right. To get the same desired product as in Figure 1, the third and final deprotection step is carried out, which removes the protecting group.

Principle 8 - waste from protecting groups

Figure 3 The waste created by all three reactions in Figure 2.

Even though the product from Figure 2 is the desired product, we had to do three reactions to only make one change, which is inefficient. Also, each step generates waste products (shown underneath each reaction arrow in the above cartoon) , which are depicted in Figure 3.

Protecting groups are a useful tool that chemists use to make the molecules, because we often need to carry out selective reactions on a molecule that has multiple of the same reactive sites. However, as we have talked about here, they are also inefficient and wasteful.

An active area of research is the development of more selective reactions, which eliminate the need to use protecting groups altogether.[1] Selective reactions use slight differences in a molecule’s chemistry to make a reaction happen at only the desired reactive site. This is very similar to the installation of the protecting group in Figure 2.

As more and more highly selective reactions are discovered, our syntheses can be made more efficient by reducing the number of steps required and the amount of waste produced. Looking ahead, protecting groups will be less and less necessary – and that’s a good thing!

 

Appendix – Example from Real Chemistry

A simple, specific example of the use of protecting groups[2] is shown below. Both oxygen-containing sites are reactive, but we only want the one on the left side to react in this case. The first reaction is the installation of the protecting group, (CH3)3SiCl, on the OH oxygen only, protecting the right side. The second reaction shows the reagent, CH3CH2CH2MgBr (for those curious, this is called a Grignard Reagent), which now reacts with just the ketone C=O site on the left, adding the desired new CH3CH2CH2 segment. The last step shows a combination of removing the protecting group to return the OH group, and also removing the [MgBr] segment of the reagent with the help of acid (shown as H3O+), which leaves the desired product with a CH3CH2CH2 chain added only on one side of the molecule.

Principle 8 - real protecting group use in chemistry

This example of a selective reaction uses a protecting group, but this requires 3 steps to only make 1 change. Instead, we can eliminate the need for protecting groups by designing new and more selective reactions that are much more efficient.

References:

[1] I. S. Young and P. S. Baran, Nature Chem. 2009, 1, 193

[2] R. J. Ouellette and J. D. Rawn, in Organic Chemistry, 2014, Elsevier, Boston pp 491-534.

Challenges in Designing Non-Toxic Molecules: Using medicinal chemistry frameworks to help design non-toxic commercial chemicals

By Shira Joudan, Education Committee Coordinator for the GCI

Throughout the past 20 years, there have been numerous reports on the state of the science of designing non-toxic molecules, including three in this year alone.1–3 The idea of safe chemicals has been around for much longer than the green chemistry movement, however it is an important pillar in what it means for a chemical to be green. In fact, many scientists agree that the synthesis of safer chemicals is likely the least developed area of Green Chemistry, with lots of room for improvement.2 For more information, see our post and video on Green Chemistry Principle #4.

One expert on designing non-toxic molecules is Stephen C. DeVishira-blog-picto of the United States Environmental Protection Agency (US EPA). In a recent paper DeVito highlights some major challenges creating safer molecules, and discusses how we can approach this challenge.1 We require a societal change about how we think of toxicity, and this shift must begin with specific education.

How can we agree upon definition of a “safe” chemical?

We need to decide and agree upon parameters that deem a molecule safe, or non-toxic. Generally, most chemists agree that an ideal chemical will have no (or minimal) toxicity to humans or other species in the environment. It should also not bioaccumulate or biomagnify in food chains, meaning it should not build up in biota, or increase in concentration with increased trophic levels in a food chain. After its desired usage, an ideal chemical should break down to innocuous substances in the environment. Potency and efficacy are also important, as well as the “greenness” of its synthesis. Setting quantitative thresholds to these parameters and enforcing them is the largest challenge.

How do we tackle the over 90,000 current use chemicals?

Although not all of these chemicals are actually in use, they are all registered under the US EPA’s Toxic Substances Control Act (TCSA), which contains both toxic and non-toxic chemicals. Many chemicals that are being used should be replaced with safer alternatives, but there are so many that it seems terrifying to know where to begin. Another replacement option is designing new technologies that don’t require the function that these chemicals provide. About two-thirds of the chemicals registered in TCSA or Environment and Climate Change Canada’s Chemicals Management Plan were in use before registration was required. Unlike pharmaceuticals and pesticides which are heavily regulated by Health Canada, commercial chemicals do not require stringent toxicity tests. But things are changing in the US and in Canada. For example, Canada has just listed 1550 priority chemicals that will be addressed by 2020. When considering replacement for chemicals of concern, the most common barrier to reducing the use is currently “no known substitutes or alternative technologies”.

How do we ensure sufficient training on the concepts of safer chemical design?

Many people making new chemicals are unfamiliar with green chemistry and basic toxicology principles. Without the proper toolbox of knowledge designing safer chemicals is challenging. [The Green Chemistry Commitment is a great place to start!] DeVito discusses the need for “toxicological chemists” which would be analogous to medicinal chemists, but instead produce non-toxic commercial chemicals. Medicinal chemists have the training to design appropriate pharmaceuticals, however commercial chemicals do not receive the same attention in terms of designing safe and efficacious products. Since humans are exposed to the commercial chemicals as well, often in intimate settings, the same attention to detail should be used during the synthetic process in order to produce safe chemicals.

Synthetic organic chemists are the ones designing the new chemicals, and we can no longer keep traditional chemists and toxicologists an arm’s length apart. Instead, there is a need for a new type of scientist that considers the function of the chemical for its desired usage and its toxicity potential to humans and the environment. Similar to the training of medicinal chemists, these chemists should receive training in biochemistry, pharmacology and toxicology, and also in environmental fate processes. DeVito suggests adding topics into an undergraduate curriculum, some of which are highlighted here:

  • Limit bioavailability: A common way to prevent toxicity has been to reduce the bioavailability of molecules. Essentially, the idea is that if the chemical cannot be absorbed into the bloodstream of humans or other species, it will not be able to cause significant toxic effects. A common predictor for bioavailability is the “Rule of 5”, where a molecule will have poor absorption if it contains more than five hydrogen bond donors or 10 hydrogen bond acceptors, a molecular weight of more than 500 amu, and a logP (or log Kow) of greater than 5.4 More sophisticated prediction methods also exist based on linear free energy relationships. A good example of low bioavailability is the artificial sweetener sucralose, where only 15% of the chemical is absorbed through the gastrointestinal tract into the bloodstream.5
  • Isosteric substitutions of molecular substituents: By removing parts of the molecule and replacing it with another functional group with similar physical and chemical properties (isosteric) toxicity can be reduced. This is common in medicinal chemistry, where it is referred to as bioisosterism, and is used to reduce toxicity, alter bioavailability and metabolism. A simple substitution can be replacing a hydrogen atom for a fluorine atom, but there can also be much larger isosteric substitutions.
  • Designing for degradation: A toxic molecule that persists in the environment can lead to global long term exposure. Understanding common environmental breakdown mechanisms can allow us to design molecules that will break down to innocuous products after their desired usage. A good starting point is understanding aerobic microbial degradation, since most of our waste ends up at a wastewater treatment plant. An important thing to keep in mind is that if a non-toxic molecule degrades to a toxic molecule, the starting material will still be of concern.

Toxicity is complicated. The best way to arm the next generation of chemists with the skills needed to design smart, safe chemicals is to tailor the undergraduate education to our new goals.

Numerous institutions, including the University of Toronto, are working towards this by signing onto the Green Chemistry Commitment!

(1)         DeVito, S. C. On the design of safer chemicals: a path forward. Green Chem. 2016, 18 (16), 4332–4347.

(2)         Coish, P.; Brooks, B. W.; Gallagher, E. P.; Kavanagh, T. J.; Voutchkova-Kostal, A.; Zimmerman, J. B.; Anastas, P. T. Current Status and Future Challenges in Molecular Design for Reduced Hazard. ACS Sustain. Chem. Eng. 2016, 4, 5900–5906.

(3)         Jackson, W. R.; Campi, E. M.; Hearn, M. T. W.; Collins, T. J.; Voutchkova-Kostal, A. M.; Kostal, J.; Connors, K. A.; Brooks, B. W.; Anastas, P. T.; Zimmerman, J. B.; et al. Closing Pandora’s box: chemical products should be designed to preserve efficacy of function while reducing toxicity. Green Chem. 2016, 18 (15), 4140–4144.

(4)         Lipinski, C. A.; Lombardo, F.; Dominy, B. W.; Feeney, P. J. Experimental and computational approaches to estimate solubility and permeability in drug discovery and development setting. Adv. Drug Deliv. Rev. 2001, 46, 3–26.

(5)         Roberts, A.; Renwick, A. G.; Sims, J.; Snodin, D. J. Sucralose metabolism and pharmacokinetics in man. Food Chem. Toxicol. 2000, 38, 31–41.

Green Chemistry Principle #7: Use of Renewable Feedstocks

By Trevor Janes, Member-at-Large for the GCI

7. A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.

In Video #7, Yuchan and Ian help us understand what a raw material or feedstock is, and why we need to choose feedstocks which are renewable.

They use CO2 as an example of a feedstock which plants convert into sugar via photosynthesis. We humans use this sugar as our own feedstock for many different delicious things, including cookies! Yuchan and Ian explain that for a feedstock to be renewable, it must be able to be replenished on a human timescale, whereas depleting feedstocks take much longer to be replenished, and are being used up at a faster rate by human activity.

Many common feedstocks are depleting, such as petroleum and natural gas. The petrochemical industry uses petroleum and natural gas as feedstocks to make intermediates, which are later converted to final products that people use, such as plastics, paints, pharmaceuticals, and many others.

An example of a renewable feedstock is biomass, which refers to any material derived from living organisms, usually plants. In contrast to depleting feedstocks like petroleum, we can much more easily grow new plants once we use them up, and maintain a continuous supply. If we can use bio-based chemicals to do the same tasks that we currently accomplish using petrochemicals, we move closer to the goal of having a steady, reliable supply of resources for the future.

Existing chemical technology has developed based on using readily available petroleum as feedstock to make a majority of chemicals and end products. However, the chemical technology that enables conversion from biomass into bio-based chemicals into final products people use is not yet as well developed.1 Chemical scientists with various specializations are currently involved in improving our ability to use biomass.2, 3

So, how can we implement the principle of renewable feedstocks on a day-to-day basis? Yuchan and Ian illustrate principle 7 through their choice of solvent. As we explore in the video for principle #5, we choose a solvent for a particular purpose based on properties such as boiling point, polarity, and overall impact on health and the environment. One more aspect to consider is that we can choose to use a solvent based on is its renewability. Tetrahydrofuran (THF) is a useful ether solvent, but it is synthesized industrially from petrochemicals (see below for synthesis), so it isn’t renewable. A close relative of THF is 2-methyl THF. Its structure and properties are very similar to those of THF, but the difference is that 2-methyl THF can be synthesized from bio-based chemicals which are made from renewable feedstocks. So when we substitute 2-methyl THF in for THF, we are putting principle 7 into action.

Synthesis of THF4 vs. synthesis of 2-methyl THF5

screen-shot-2016-10-25-at-10-35-31-pm

The synthesis of THF.

An early step in the industrial production of THF involves reaction of formaldehyde with acetylene to make 2-butyne-1,4-diol. This intermediate is hydrogenated and cyclised in two more steps to yield THF. The acetylene input is derived from fossil fuels, which again are non-renewable.

screen-shot-2016-10-25-at-10-35-48-pm

The synthesis of 2-methyl THF.

An alternative to THF is 2-methyltetrahydrofuran, which has a very similar structure to THF.  It can be synthesized starting from biomass; after conversion to C5 and C6 sugars and subsequent acid-catalyzed steps, the intermediate levulinic acid can be hydrogenated to yield 2-methyl THF.

References:

  1. “Renewable Feedstocks for the Production of Chemicals” Bozell, J. J. ACS Fuels Preprints 1999, 44 (2), 204-209.
  2. “Conversion of Biomass into Chemicals over Metal Catalysts” Besson, M.; Gallezot, P.; Pinel, C. Chem. Rev. 2014, 114 (3), 1827-1870.
  3. “Transformation of Biomass into Commodity Chemicals Using Enzymes or Cells” Straathof, A. J. J. Chem. Rev., 2014, 114 (3), 1871-1908.
  4. “Tetrahydrofuran” Müller, H. in Ullmann’s Encyclopedia of Industrial Chemistry 2002, 36, 47-54.Wiley-VCH, Weinheim. doi:10.1002/14356007.a26_221
  5. “Synthesis of 2-Methyl Tetrahydrofuran from Various Lignocellulosic Feedstocks: Sustainability Assessment via LCA” Khoo, H. H.; Wong, L. L.; Tan, J.; Isoni, V.; Sharratt, P. Resour. Conserv. Recy. 2015, 95, 174.

UofT Demonstrates its Commitment to Sustainable Chemistry

“We’re very pleased and proud to announce that the Chemistry Department has recently joined the Green Chemistry Commitment (GCC)!” – Dr. Andy Dicks, University of Toronto, Associate Professor

gci-group-photo-sept27-2016

GCI Members Fall 2016

The University of Toronto has recently signed the GCC making us the first school outside of the United States to sign onto this impactful commitment, which now contains 33 colleges and universities. The GCC is overseen by Beyond Benign, a United States not-for-profit organization created by Dr. Amy Cannon and Dr. John Warner, a founder of the principles of green chemistry. Within the GCC, academic institutions collaborate to share resources and know-how in order to positively impact how the next generation of scientists are educated about sustainability issues. Participating departments commit to green chemistry instruction as a core teaching mandate. The aim is to provide undergraduates and graduates with the required understanding to make green chemistry become standard practice in laboratories around the world. This, in turn, ensures that when graduates of the university enter the workforce, they are armed with the knowledge of how to make molecules and processes more sustainable and less toxic by adhering to the Twelve Principles of Green Chemistry.

The GCC unites the green chemistry community around shared goals and a common vision to grow departmental resources to allow a facile integration of green chemistry into the undergraduate laboratories as well as to improve connections with industry which creates job opportunities for sustainability-minded graduates. Their website offers many resources for those interested in reading actual case studies and laboratory exercises, so please click here to visit their website and be informed!

Our chemistry department has already improved the green chemistry content in our undergraduate laboratories by updating the first year courses and upper year synthetic chemistry courses to include various graded questions about the Twelve Principles as well as ensuring the undergraduates are thinking about how they could make their current lab protocols more sustainable. Additionally, students can choose to study the fate of chemicals in our environmental chemistry courses offered. Of course there’s always room to improve, so the Green Chemistry Initiative (GCI), in collaboration with Dr. Andy Dicks, is working on evaluating the undergraduate chemistry curriculum’s current focus on sustainable chemistry and toxicology, in hopes to further improve our undergraduate’s learning experience. The GCI also provides many educational opportunities to department members such as our Seminar Series as well as many outreach opportunities, making our group a driving force in the integration of green chemistry principles to the department. Lastly, the University of Toronto chemistry courses reach thousands of students a year, and by being the first Canadian university to sign this commitment, we are working towards a greener future in Canada!

Thank you for celebrating this very momentous achievement with us!
Karl Demmans, Ian Mallov, Shira Joudan, and Laura Reyes

The Importance of Green Chemistry Education at the Undergraduate Level

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.

 

GCI figure May 2016

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:

  1. 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.

A Healthy Scientist Makes Greener Science

By Kiril Fedorov, Member-at-Large for the GCI

Do you remember the time you had spilled your reaction vessel on the floor, over distilled the solution, broke glassware, or had another accident in the laboratory?  Accidents happen to everyone so it is likely to happen to you once or twice in the laboratory. A problem emerges when these incidents become consistent, which is clearly not a green practice for scientists.

For example, let’s say you had a long week of reactions and you destroyed the whole product of your main reaction. This not only means you have destroyed your product, it also means you have wasted the following items: solvents, electrical energy, glassware (if broken or contaminated), single use items (pipette tips, napkins, scintillation vials etc.).

Kiril blog_picture

Comparison of materials required for a normal vs. tired student.

 

Although accidents are random, their frequency may not be. Do you remember why many of those mistakes happened?   There could be many reasons but there is one in particular I would like to highlight. It is your health. First of all people who are healthy are less prone to mistakes and as a result are more efficent.1,2,3 For example when nurses were tested on their work on long shifts, the majority of mistakes that happened were at the end of the shift when they were most tired. You are no different as a scientist, engineer, journalist, editor or any other student. Each morning there is a long line at Tim Hortons for coffee to keep those people who are drinking it alert. Also, many people grab fast food at lunch, eat too fast, and experience a really sleepy afternoon due to high fat load or sugar crash. This leaves people tired, less aware, and as a result prone to mistakes.

Several articles highlight how much loss to the economy is due to poor health. Also people with poor health have to take more medications and get more blood tests, which again is less green.

So what can you do?

The 7 rules of green laboratory:

  1. Be punctual

If you are in a rush anxiety rises, mineral levels drop 4-7 and mistake levels increase.

  1. Prioritize

When tasks are organized you are less likely to make a mistake and again lower anxiety due to less multitasking.

  1. Sleep at night

Night is for sleeping for people! Do not stay out late if your experimental work starts early the next day. Only stay awake if you really have to. If you are a night owl, then maybe your schedule is different, but remember if you are consistently tired or need coffee it is not very efficient.

  1. Eat healthy

No need to be a health lunatic but improving your diet always works to your advantage. Let’s face it: stomach aches, sugar withdrawal, headaches, heartburn or other problems keep you distracted from lab work.  You are significantly prone to mistakes.

  1. Exercise

Get off your seat from the lab every 40-50 minutes and stretch for 10 minutes. Go outside and breathe some fresh air while walking. It will get your blood pumping and get your brain working better. (You might invent a greener reaction)

  1. Follow safety instructions

Remember it is not just about an instructor or your supervisor who enforce safety rules, but yours and other people’s health. Take your safety seriously! Think of it this way: after all the years of training as a scientist (very costly on chemicals) suddenly your health and efficiency drops and you are about to discover something amazing.

  1. Have fun

Bored, angry or sad people tend to be more prone to mistakes. (Common sense). If you believe in Karma this is quite self-explanatory. But for those who don’t, think about the times something did not work and likely you would give up or break something. With a little happy thought you can think more clearly and everything gets solved better. Just try it, I am telling you it works.

 

Here is an example of a reaction and the cost of avoidable mistakes:

Synthesis of Moclobemide

 Compounds used Amount required (used by an alert student) Amount used  for a tired student

(estimates)

Amount used  for  a repeated experiment
4-(2aminoethyl)morpholine 0.5 ml 0.5-1 1 ml
4-chlorobenzoyl chloride 0.48 ml 0.48-1 1 ml
Triethyl amine 20 ml 20 -40 40 ml
10% aq ammonia 10 ml 10-20 20 ml
Dicloromehtane 2X10 ml (2-4)X10 4X10ml
Isopropanol ~20 ml 20-40ml 40 ml

 

Other compounds/items Amount estimates
Water (for glassware washing) 1-20 L
Paper towels 1-30
Electrical power 0.5hr X 4kw+ 0.5 1.5 KW= 2.75 – 5.50 KWh used
Syringe 1
Acetone 10-30 ml (washing NMR tubes)
Soap  
Magnesium sulfate A few grams

 

References:

1. Health and safety executive survey United Kingdom http://www.hse.gov.uk/statistics/dayslost.htm

2. Tired Doctors More Prone to Errors
Tired Doctors More Prone to Errors

3. Patient care may be at risk from tired staff on long shifts. Nurs Manag (Harrow) 2015;22(5):6. https://hbr.org/2015/08/the-research-is-clear-long-hours-backfire-for-people-and-for-companies

4. Sartori SB, Whittle N, Hetzenauer A, Singewald N. Magnesium deficiency induces anxiety and HPA axis dysregulation: Modulation by therapeutic drug treatment. Neuropharmacology 2012; 62(1):304-312.

5. Uteva AG, Pimenov LT. Magnesium deficiency and anxiety-depressive syndrome in elderly patients with chronic heart failure. Adv. Gerontol. 2012; 25(3):427-432.

6. Grases G, Pérez-Castello JA, Sanchis P, Casero A, Perelló J, Isern B, et al. Anxiety and stress among science students. Study of calcium and magnesium alterations. Magnes. Res. 2006; 19(2):102-106.

7. Singewald N, Sinner C, Hetzenauer A, Sartori SB, Murck H. Magnesium-deficient diet alters depression- and anxiety-related behavior in mice – Influence of desipramine and Hypericum perforatum extract. Neuropharmacology 2004; 47(8):1189-1197.

Green Chemistry Principle #6: Design for Energy Efficiency

By Trevor Janes, Member-at-Large for the GCI

6. Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.

In chemistry (and in life) we need energy to do work. Every task we do in the lab requires energy: whether we’re using a Bunsen burner or weighing out a reagent or dissolving our favourite compound, in all cases we’re using energy in some form.

In the lab, we often need to change the pressure and temperature of experiments, and this uses a large amount of energy. Ideally, we would perform all reactions at ‘ambient’ conditions – room temperature and atmospheric pressure – in order to minimize energy usage.

In Video #6, Julia and David use an energy monitor to see help us see just how much energy is used by everyday lab equipment. They measure a vacuum pump, which is used to reduce pressure, and a hot plate, used to raise the temperature of a reaction.

Julia and David measure the power used by each instrument and calculate the monthly energy bill, comparing the cost and amount of energy to a regular household item like a TV.[1] By doing this they determine the financial impact of the energy requirements of lab equipment. A hot plate uses roughly as much energy as a TV, and a vacuum pump uses more energy than 3 TVs! Just like at home, minimizing the use of equipment in a lab, and turning off equipment when it’s not in use, will conserve energy and save money.

In an academic lab, the amount of energy and its associated cost is modest and may seem insignificant. But on the much larger industrial scale, energy/money savings are multiplied and energy efficiency becomes even more important.

We know that heating a reaction requires energy, but another energy-intensive aspect of lab work that occurs after completion of the reaction is the work-up. “Working up” the reaction means separating our desired product from the other components in the reaction mixture such as solvent and byproducts. We talked about this before in our post for Principle #5.

To remove solvent conveniently we use a rotary evaporator, commonly referred to as a “rotovap,” which involves the combined use of a heat source, vacuum pump, rotating motor, and chiller. The heat, vacuum, and rotation vaporize the solvent and the chiller condenses the solvent vapors into a flask for removal. If you’re curious, we also measured the energy used by the chiller component of the rotovap assembly (see calculations below). If left on all the time, the monthly energy bill for the chiller alone would be $15.60 – the same as 2 TVs – and that’s not including the other rotovap components. If we can develop chemical reactions that avoid solvent removal and/or simplify work-up, we can save energy and money.

justshutit

Our “Shut It” campaign encourages fume hood sashes to stay closed.

Later in the video, we were delighted to host special guest Allison Paradise, Executive Director of My Green Lab who joined us to highlight the importance of minimizing the energy used by chemical fume hoods. As the My Green Lab website explains, there are Constant Air Volume (CAV) and Variable Air Volume (VAV) ventilation systems.[2] In VAV systems, closing the fume hood sash allows the exhaust fan to run more slowly while maintaining a safe flow rate. By closing our sashes in VAV systems we can reduce energy use by 40% or more!

Turning off your TV after you’re finished watching it illustrates the idea behind Principle #6. Just like you care for the environment and save money by being energy efficient at home, we want to minimize the environmental and economic impacts of the chemical processes we do in the lab.

Energy Calculations:

Julia and David measured the vacuum pump to draw 360 W. If we kept it on for one month, this would be 259 kWh. In Toronto, the consumption-based cost of electricity is $0.108/kWh,[1] which makes the cost for one month of vacuum pump use $28.

360 W x (1 kW/1000 W) x (720 h/1 month) = 259 kWh/month

259 kWh x $0.108/kWh = $28

The hot plate heating an oil bath to 110 °C uses 100 W, which amounts to 72 kWh in one month. Using the electricity cost of $0.108/kWh again, the monthly bill for keeping the hot plate on at all times would be $7.80.

100 W x (1 kW/1000W) x (720 h/1 month) = 72 kWh/month

72 kWh x $0.108/kWh = $7.80

Not included in the video is the measurement of a rotovap chiller. This chiller circulates coolant that it maintains at -5 °C, which requires 200 W. This is double the power drawn by the hot plate and represents a monthly energy bill of $15.60.

References:

[1] Cost of electricity and household appliance energy usage, Toronto Hydro: http://www.torontohydro.com/sites/electricsystem/residential/yourbilloverview/Pages/ApplianceChart.aspx

[2] My Green Lab’s explanation of fume hood types and their energy consumption: http://www.mygreenlab.org/be-good-in-the-hood.html