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.

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.

Just Shut It!

By James LaFortune and Shawn Postle, Members-at-large for the GCI

The Green Chemistry Initiative (GCI) and the University of Toronto constantly strive to reduce the environmental impact inherent to research in the Chemistry Department.  A major contributor to the department’s carbon footprint is its fume hoods, which are required to safely carry out experimentation with volatile solvents or reagents.  They provide a partially enclosed working space that draws air from the laboratory into the hood, thereby reducing the researcher’s exposure to chemicals. However, this requires replacing the removed air with acclimatized outside air, a process which consumes large amounts of energy in heating or cooling the air.

Fume hoods are designed with a height-adjustable glass pane (sash) that allows the researcher to work while keeping the space as enclosed as possible. There are two main types of fume hoods used in chemistry labs: constant air volume (CAV) and variable air volume (VAV).  With CAV, the air flow remains constant regardless of sash height, while VAV systems are designed to moderate air flow based on the sash height.  Each fume hood requires roughly as much energy as three American households when in use.  However, roughly 50% of this energy can be conserved in VAV systems if the sash is kept shut.  Given that the Chemistry Department has 123 VAV fume hoods, ensuring that VAV sash heights are minimized during idle periods is an effective strategy to reduce unnecessary energy consumption.1

james_shawn-blog

The GCI’s Just Shut It! Campaign, renewed this past summer for its third season since 2008, encourages graduate students to close VAV fume hood sashes during idle times and to minimize sash height when working in the hood.  Fume hoods are checked weekly by GCI volunteers to ensure compliance and users of fume hoods found to be in compliance are entered into monthly prize draws.  The past two Just Shut It! Campaigns (read more about the original campaign) were very successful, where compliance rates increased from 3% to 61% during the campaign. Since its reinvigoration over the summer, we have recorded similar compliance levels as previous campaigns.

What’s more, the Chemistry Department currently only uses VAV fume hoods in its Davenport wing.  However, it is exploring air systems renovations, including replacing CAV with VAV fume hoods in much of the Lash Miller wing.  These additional VAV fume hoods will further decrease our environmental impact.

This time around, we are looking to keep the Just Shut It! Campaign going permanently.  Gracious thanks to the Department of Chemistry for funding this campaign, especially Chief Administrative Officer Mike Dymarski.

  1. E. Feder, J. Robinson and S. Wakefield, International Journal of Sustainability in Higher Education, 2012, 13, 338-353.
Leading by Example in the Lab

Leading by Example in the Lab

By Ian Mallov, Co-Chair for the GCI

Ask a scientist what their greatest satisfaction is from research.  Most will probably tell you something along the lines of “the pursuit and discovery of new knowledge.”

Some will mention the parallel satisfaction of originating inventions or techniques that are broadly applicable, and seeing that work applied for the benefit of society.

Much of the challenge of moving towards a truly sustainable culture is in applying what we’ve already shown to be effective on small scales.

Two years ago, the Green Chemistry Initiative’s 2014 Workshop team developed ten recommendations entitled “Simple Techniques to Make Everyday Lab Work Greener.”  Led by co-founder Laura Hoch, with important contributions from Cookie Cho and Dr. Andy Dicks, we publicized these during the workshop.  So what has happened to these recommendations since?  They’ve been developed – are researchers in our department incorporating them into their work habits?  Are we ourselves applying what we already know to be effective?

I was pleasantly surprised to find out that a number of our researchers were in fact using these greener lab techniques.  In an effort to make their use even more widespread, I’d like to highlight some examples of researchers in our department who are leading by example.

Further, next week our “Simple Techniques to Make Everyday Lab Work Greener” poster will be posted around the department!


Ian_July blog 1

 

Scientist: Karlee Bamford, Stephan lab

Technique: Recycling solvents from rotovap to use for cleaning vials and glassware

Why it’s greener: Saves solvent, reduces waste generated, and reduces energy used in production and disposal of additional solvent

Issues to Consider: Use in synthesis and purification often requires solvents to be more pure than those collected from rotovap


Ian_July blog 2Scientist: Aleksandra Holownia, Yudin lab

Technique: Setting GC to stand-by mode when not in use

Why it’s greener: The GC uses much less helium gas (a rapidly diminishing resource) and reduces the temperature of the oven, saving energy

Issues to Consider: Does take a few minutes to start up again


Ian_July blog 3Scientist: Karl Demmans, Morris lab

Technique: Using 2-methyl THF as a reaction solvent instead of THF

Why it’s greener: 2-methyl THF is derived from the aldehyde furfural, sourced from renewable crops.  THF, on the other hand, is derived from fossil fuels.  While crop-sourcing does not automatically make it “greener,” consensus in the case 2-methyl THF is that it is indeed less energy- and resource-intensive to produce than THF.

Issues to Consider: Unlike THF, it is immiscible with water.  Slightly less polar than THF


Ian_July blog 4Scientist: James LaFortune, Stephan lab

Technique: Isopropanol/dry ice instead of acetone/dry ice for cold baths

Why it’s greener: An Isopropanol/dry ice bath maintains a temperature of -77 oC, almost exactly the same as acetone/dry ice’s -78 oC.   However, isopropanol is much less volatile (bp: 83 oC) than acetone (bp: 56 oC); practically, this allows for the recovery and reuse of the isopropanol after several hours or overnight, while acetone evaporates.

                                                                          Issues to Consider: Must actually recover and reuse the isopropanol!


Ian_July blog 5

Scientist: Samantha Smith, Morris lab

Technique: Closing the fume hood sash when not in use.

Why it’s greener: Modern, variable-flow fume hoods – used in the Davenport wing of our building – regulate the strength of their vacuum for safety based on how far open the fume hood is.  When wide open, the fume hood uses much more energy than when closed (see Just Shut It campaign!)

Issues to Consider: Is your fume hood variable-flow?

 


Ian_July blog 6Scientist: Brian de la Franier, Thompson lab

Technique: Using a closed-loop cooling system for refluxes and distillations.

Why it’s greener: Uses much less water.  While some of our undergraduate labs have built-in closed-loop cooling systems, Brian simply got a small fish tank pump from a pet store and uses a Styrofoam box with ice to keep his water cold – a very easy DIY solution!

Issues to Consider: Does water saved compensate for the extra energy for the ice/pump?  Consider the energy used to purify and deliver the extra water and we can safely say yes.


Ian_July blog 7

Scientist: Alex Waked, Stephan lab

Technique: Reusing rubber septa used to seal Schlenk flasks

Why it’s greener: Saves materials and money

Issues to Consider: There is a limit to their reusability.  At some point, if a septum has been perforated by too many needle holes it is no longer an effective seal.  Must also ensure septa are kept clean.


Ian_July blog 8

Scientist: Molly Sung, Morris lab

Technique: Reusing gas chromatography vial caps by replacing their septa

Why it’s greener: Saves materials and money

Issues to Consider: Somewhat time-consuming to remove and replace rubber septa for each cap

 


Ian_July blog last

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

Update on the Waste Awareness Campaign

By Karl Demmans, Seminar Series Coordinator for the GCI

Today I’m very excited to update everyone on the latest results of the Waste Awareness Campaign. We’ve been recording the types and quantities of waste accumulated in Lash Miller Chemical Laboratories since January 1st, 2014.

Posters displaying the data collected in the first 8 months were posted throughout the department, with the intention of drawing researchers’ attention to their waste habits and shedding light on alternate green methods to help reduce waste generated in our department. You may have seen this previous data set, which we published in a blog post here.

Now, almost two years later, we have gathered enough data to look at the changes in waste production from 2014 to 2015, during the period of January to August for each year. Take a look at the poster below for a summary of what we found.

GCI Waste Awareness Poster 2015

The table shows the percent contribution by discipline to each waste category, while the bar graph displays the distribution of waste within each discipline.

Beginning with the table at the top, the rows display each discipline’s percent contribution to each respective waste category, while the last column shows the contribution to total waste in 2015. The value in brackets denotes the change from the same period in 2014. Understandably and not surprisingly, the most waste is produced by organic chemistry labs, accounting for 81% of flammable waste, and 58% of the total waste in our department. This is then followed by the polymers & materials, inorganic, and biological disciplines, fairly evenly contributing 10-15% each to the total waste volume.

Subsequently, the row entitled “Percent of Total 2015” breaks down the contribution by each type of waste compared to the total waste accumulated. From this, we can see that the flammable waste was our department’s largest source of waste this year, followed by green pails for solid waste at 40%. The last row indicates the percent increase for each waste category in comparison to the same period of 2014.

Surprisingly, we observed a fairly dramatic increase in waste this year. It is important to note that the data has already been corrected for the number of graduate students and post-doctoral fellows working in the labs, since this number fluctuates constantly. However, we do not have the number of undergraduate students who work or volunteer in each lab, which could adjust the data comparisons. Nonetheless, the increase in waste production surprised us, and we will continue to compare trends as we collect more data over time.

The bar graph “Waste Distribution by Discipline” at the bottom of the poster displays a further breakdown of the types and quantities of waste produced in each discipline of chemistry. For example, in Environmental Chemistry, 51% of the total waste was green pails while only 25% of waste was flammable solvent. This graph allows each lab to identify their largest type of waste production and strategically target reduction. In general, the vast majority of the Chemistry Department’s waste was flammable and solid material. In fact, we are only producing minimal halogenated and acidic waste, which is a noteworthy accomplishment as these types of waste are more harmful to the environment and costly to neutralize.

While we have seen a percentage shift in the use of chlorinated and acidic to flammable solvents, we have still noted increases across the board in each waste category. As a research facility, we generally produce a very small fraction of the global chemical waste in comparison to industrial processes. Nonetheless, we take our waste production very seriously and are always brainstorming ways to encourage less production of chemical waste in order to reduce our footprint. Do you have any stories of how your institutions have encouraged waste reduction? Share with us in the comments!

For more information on the categories of waste and proper waste disposal please refer to our posts Proper Chemical Waste Disposal: Posters & Memes and Chemical Waste FAQs.

Green Chemistry Education through TAs at the University of Toronto

By Julia Bayne, Member-at-Large for the GCI

Green chemistry education is one of our main initiatives within our chemistry department. As part of an ongoing collaboration, we, the Green Chemistry Initiative (GCI), work with the teaching faculty to help modify and improve the undergraduate curriculum through the incorporation of green chemistry. This partnership has resulted in a substantial increase in the amount of green chemistry taught in the classroom and the modification or replacement of a number of experiments in the laboratory component of these courses. For example, the University of Toronto offers a third year undergraduate chemistry course (CHM343H: Organic Synthesis Techniques) that has undergone a complete transformation and now largely emphasizes the main concepts of green chemistry. Not only is the theory discussed in lecture, but the students are also strongly encouraged (and graded on their ability) to integrate green chemistry practices into their experiments in the laboratory.[1]

Green Chemistry for TAs Handout - page 1

We created this handout to encourage TAs to teach their students the basics of green chemistry [PDF].

Although this initiative has emphasized educating the undergraduate students, we found that the teaching assistants (TAs) and laboratory demonstrators did not always have a strong training in green chemistry themselves, and therefore did not necessarily feel comfortable teaching green chemistry concepts to their students. With this in mind, our next goal was to create a handout for TAs that would contain a concise explanation of green chemistry, along with some tips that they could use to help encourage students to align their thinking with the 12 principles of green chemistry. This handout, entitled “Tips for Teaching Green Chemistry to Students (pdf)” contains a brief explanation of green chemistry and lists the 12 principles of green chemistry with a short summary to highlight each one. The handout also includes suggestions on how to encourage undergraduate students to properly implement these principles into their laboratory practice.

Subsequently, we chose to highlight four key teaching points (pdf) through fun graphics that help emphasize the importance of green chemistry in the lab. The key points are as follows: 1) Work on a small scale, 2) A higher LD50 (median lethal dose) value typically indicates a safer chemical, 3) Minimize solvent use when washing glassware, and 4) Separate waste in the correct container so it can be disposed of accordingly. By simplifying and highlighting these important points, we hope that TAs will feel more comfortable teaching a few basic green chemistry concepts to their students, and similarly, we hope that the students will gain a better understanding of how to apply the principles of green chemistry to real-world situations in the laboratory.

Green Chemistry for TAs Handout - page 2

Starting from the perspective of undergrad labs, we picked these 4 key green chemistry teaching points to emphasize to the TAs [PDF].

We anticipate that by reaching out to the graduate students who teach the lab component of the undergraduate courses, they will themselves be more comfortable and excited to teach students about green chemistry, including the straightforward substitutions and modifications it has to offer. Ultimately, we hope to see more enthusiasm among the undergraduate students as they grasp the importance and benefits of including green chemistry in the laboratory component of their courses and potentially research laboratories in the future.

References:

[1] Edgar, L. J. G.; Koroluk, K. J.; Golmakani, M. and Dicks, A. P. J. Chem. Ed. 2014, 91, 1040-1043.