Rules to Design By: Green Chemistry Principles
While researching an article on Green Chemistry for the upcoming Non-Toxic Times (which, keep your fingers crossed, will come out next week), I stumbled across an entry on the same subject in the ever amazing Wikipedia that contained something I didn’t know existed: a set of principles to guide chemists in greening their labs and the things those labs create.
Principles, of course, are always a good thing because they set certain benchmarks and establish concrete guidelines for whatever it is we’re trying to do. Whenever a decision comes up as we proceed, we can compare all our possible choices to the principles at hand. When we do, we often find that there’s no decision to be made at all. The principles make it for us. They may even suggest that we drop the current operation entirely and try something else.
In the case of green chemistry, the 12 principles were created to steer chemists away from toxic substances and processes, and encourage healthier alternatives. I can’t for a moment pretend to know what some of these are about. (“Stoichiometric reagents, for example, is a pretty scary term. I think I had a beaker or two of that at a really ugly frat party once…), but than again why should I? They’re not for me. They’re for the people who are actually out there mixing up the molecules. The people who need to stop messing with nature and start working with it instead. They’re only for you and I in the sense that as they ripple through the chemical community, they’ll eventually trickle down to us in the form of safer, healthier, non-toxic alternatives to today’s hazardous products and processes. You’ll never use them yourself, but you will someday end up using the stuff they lead to, and we’ll all be a lot healthier for it.
When it comes to chemistry and all the substances it’s constantly unleashing on the world (The EPA gets approval applications for roughly 2,000 new chemicals every year–more than five new materials every day), it’s obvious that some guidance has definitely needed but clearly been lacking. The 12 Principles of Green Chemistry provide this missing ingredient. If even just one chemist takes them to heart and decides to design differently, they’re working. If they spread and inspire a whole new generation of researchers, which they appear to be doing (see the upcoming article in the newsletter), then we’re really getting somewhere we desperately need to go. Either way, I was glad to see the ideas behind green chemistry codified in a practical way that scientists can actually use. It’s a sign that the good guys are gaining ground.
Here are the 12 Principles:
- Prevent waste: Design chemical syntheses to prevent waste, leaving no waste to treat or clean up.
- Design safer chemicals and products: Design chemical products to be fully effective, yet have little or no toxicity.
- Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to humans and the environment.
- Use renewable feedstock: Use raw materials and feedstock that are renewable rather than depleting. Renewable feedstock are often made from agricultural products or are the wastes of other processes; depleting feedstock are made from fossil fuels (petroleum, natural gas, or coal) or are mined.
- Use catalysts, not stoichiometric reagents: Minimize waste by using catalytic reactions. Catalysts are used in small amounts and can carry out a single reaction many times. They are preferable to stoichiometric reagents, which are used in excess and work only once.
- Avoid chemical derivatives: Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate waste.
- Maximize atom economy: Design syntheses so that the final product contains the maximum proportion of the starting materials. There should be few, if any, wasted atoms.
- Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If these chemicals are necessary, use innocuous chemicals. If a solvent is necessary, water is a good medium as well as certain eco-friendly solvents that do not contribute to smog formation or destroy the ozone.
- Increase energy efficiency: Run chemical reactions at ambient temperature and pressure whenever possible.
- Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.
- Analyze in real time to prevent pollution: Include in-process real-time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.
- Minimize the potential for accidents: Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.