Green Chemistry Principle #9: Catalysis

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

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

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

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

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

Principle 9 Figure 1 - catalysis

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

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

Principle 9 Scheme 1 - catalysis example

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

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

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

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

Proper Chemical Waste Disposal: Posters & Memes

By Cookie Cho, Member-at-Large for the GCI

One of the unfortunately inevitable aspects of doing research is creating chemical waste. Previously, we have launched a Waste Awareness Campaign to try to reduce the amount of waste produced, and hosted a lecture on Chemical Waste FAQs to encourage proper waste disposal.

In the chemistry building at the University of Toronto, two general types of groups produce chemical waste: the research chemists, and undergraduate students.

Recently, the GCI partnered with UofT’s Environmental Health and Safety (EHS) office to develop and distribute an easy-to-follow waste disposal poster. This guide was designed to answer common questions about proper sorting of waste classes, and to make it easier for the research chemists to dispose of their chemical waste. These were then posted in all research labs throughout the chemistry building. We have received great feedback from many department members so far, including the researchers themselves and administrative staff!

waste poster

Fig. 1: Waste Disposal Poster, produced in partnership with EHS and GCI.

In order to guide the undergraduates, many of whom have never worked in a chemistry lab before, we developed a series of meme-themed posters to point out proper chemical disposal in undergraduate laboratories. Through the use of humour and easily recognized images, our goal was to help the undergraduates remember that proper disposal of chemical waste is the right thing to do. Here are some of the memes we developed.

Archer meme

Fig. 2: Archer meme – Chemical waste goes in waste containers, not down the drain!

Lumbergh meme

Fig. 3: Lumbergh meme – Lumbergh insists that chemical wastes be disposed of properly.

World's Most Interesting Man meme

Fig. 4: World’s Most Interesting Man disposes acid waste properly.

Currently, we are also collaborating with course instructors to develop more formal diagrams and materials, in order to better train new undergraduates on proper chemical waste disposal. We welcome any ideas that our readers may have! How is chemical waste disposal taught and encouraged at your institution?

Chemical Waste FAQs

By Peter Mirtchev, Member-at-Large for the GCI and Laura Reyes, Co-Chair for the GCI

All chemists create chemical waste, it’s simply part of our job. Recently, we started a Waste Awareness Campaign to track the amount of waste being generated by our chemistry department. Aside from this, the chemical waste disposal process was a bit of a mystery. Learning how to properly sort, label, and dispose of chemical waste should be part of every chemists’ early training, but typically gets overlooked. In academic research labs, waste disposal habits tend to get passed down from one person to the next, and often stem from tradition rather than regulation. With this post, we hope to clarify some of the confusion surrounding proper disposal of different types of chemical waste.

We recently co-hosted a seminar about waste disposal with the Chemistry Students’ Union. Our speakers were Ken Greaves (Chemistry Department Supplies & Services Supervisor) and Rob Provost (Environmental Protection Manager at the UofT EH&S Office). We found that many members of the department had important questions regarding proper disposal practices and what happens to chemical waste after it is picked up. We have summarized the crucial points of the talk in Q&A format below. There’s also very useful information at this EH&S website on chemical waste. If you have other unanswered questions regarding chemical waste, leave them in the comments and we’ll get them answered for you!

Disclaimer: the information below is specific to the Department of Chemistry at the University of Toronto, and may change according to institution. Check with your own institution regarding the rules of chemical waste disposal.

Q: What are the most common types of chemical waste produced in a research laboratory?

A: Solvents. At the University of Toronto, the three most common chemicals are 1) acetone, 2) hexanes, and 3) dichloromethane. The Department of Chemistry purchases over 10,000L of acetone per year alone.

Q: What is considered ‘flammable’ waste?

A: A flammable liquid is one that has a flashpoint of 23.8°C or lower.

Q: Is a mixture of water and organic solvents considered aqueous or flammable waste?

A: If the mixture is more than 50% water, it is considered aqueous waste. If it is less than 50% water, it is considered flammable waste. If the amounts are uncertain, treat as aqueous (see below for more about the treatment of waste types).

Q: What mixtures are treated as chlorinated waste? Continue reading

Waste Awareness Campaign

By Karl Demmans, Workshop Coordinator for the GCI

Welcome back to the GCI’s monthly updates about our recent endeavors and findings in green research! Today I’d like to discuss the efforts put forth by various faculty and graduate students over the past eight months to collect and distribute data about the amount of waste produced in the Lash Miller Chemical Laboratories, the main building for the Department of Chemistry at UofT. Our hope is that once students are presented with this information, they will be more conscious about their chemical procedures and consider alternate green methods to help reduce waste. For an example of the types of data we have collected, take a look at the poster found below.

Waste Poster GCI

Waste data for Lash Miller Chemical Laboratories (Department of Chemistry, University of Toronto).

In Lash Miller, waste collection occurs every Friday. Each research group gathers their labelled waste containers and brings them to  our waste department for sorting and temporary storage, before eventual disposal.  The rather colourful chart in the poster displays the amount of solid or solvent waste, broken down for each chemistry discipline, concluding with the percent of total waste each discipline produces, as well as the type of waste that is made.

The colour gradient of the five waste categories denotes the combined environmental and economic concerns ranging from solid decontaminated waste (‘best’) to acidic waste (worst). Overall, the waste picture for Lash Miller looks pretty good, with only 9% of the total waste produced in the building coming from the two red categories (acidic and chlorinated). By specifically targeting these types of waste for reduction, we can continue to improve and make the waste profile of our department even better.

For Lash Miller graduate students, if you’d like to know specifically how much waste your group is producing, send an inquiry e-mail to green [at]!

Lastly, the final part of the poster describes what each type of waste is, and explains the disposal process. The topic of how chemical waste is disposed of was recently discussed during our last GCI seminar. Click here to read our Chemical Waste FAQs!

In the upcoming months there will be another poster displaying the percent reductions in waste produced per discipline, to see how graduate students react to the current information. Thanks for stopping by to learn about our Waste Awareness Campaign and how we are helping to reduce our environmental footprint.

Green Chemistry Principle #3: Less Hazardous Synthesis

By Kenny Chen, Member-at-Large for the GCI and Laura Reyes, Co-Chair for the GCI

3. Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.

The idea of practicing safe chemistry sounds intuitive, but contemporary technology, policy, and knowledge of long-term health and environmental impacts are often limiting factors in determining how safe a process is. In other words, scientists are always working with what they have in terms of technology and knowledge of hazards, and that story may change as we learn more.

In our video, we briefly described the recent history of technologies used to generate chlorine gas, focusing on the transition from mercury cell processes to membrane cell processes.

Chlorine has been produced industrially since the 19th century, when it was widely used in textiles and paper industries. Nowadays, it is essential in many plastics and chemical industries, for example to make the plastic polyvinyl chloride or PVC.

In the past, the mercury cell process was widely used to make chlorine. We now know that resulting contamination from mercury waste has tragic health and environmental effects, but that was not always the case due to previous limitations in technology, knowledge of heavy metal accumulation, and resulting policies. For example, as we talk about in the video, the mercury cell-based chloralkali process caused the infamous case of Minamata disease that struck Ontario in 1970, severely affecting two native communities.

Now, the membrane cell is the preferred choice for the chloralkali process. The increased use of this cellulose-based technology has resulted in decreased use of the mercury cell, which in turn has reduced mercury emissions into the environment.

Despite large improvements, even in 2013 more than 5 tonnes of mercury were released into the environment due to the chloralkali process, which leaves significant room for improvement as we move forward, whether by improved technology or stricter regulation.

Sometimes, we can’t help but learn new information over time about the long-term safety of technologies and chemical processes. Even so, we must use the knowledge that is available at all times so that we can create and modify processes that are less hazardous by design. In this way, we will have inherently safer chemistry by keeping green chemistry principle #3 in mind.


Handbook of Chlor-Alkali Technology – History of the Chlor-Alkali Industry (

Best Available Techniques (BAT) Reference Document for the Production of Chlor-alkali (

Chlorine Industry Review 2013-2014 (