What’s green chemistry?
Green chemistry is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances. Whereas Environmental Chemistry is the chemistry of the natural environment, and of pollutant chemicals in nature, green chemistry seeks to reduce and prevent pollution at its source. In 1990 the Pollution Prevention Act was passed in the United States. This act helped create a modus operandi for dealing with pollution in an original and innovative way. Environmental chemistry thus deals with contaminants and their elimination. Green chemistry avoids pollution by utilizing processes that are ‘benign by design’ (what has been named industrial ecology).
As a chemical philosophy, green chemistry derives from organic chemistry, inorganic chemistry, biochemistry, analytical chemistry even physical chemistry . However, the philosophy of green chemistry tends to focus on industrial applications. Contrast this with click chemistry which tends to favor academic applications, although industrial applications are possible. The focus is on minimizing the hazard and maximizing the efficiency of any chemical choice. Again, we should emphasize that it is distinct from environmental chemistry which focuses on chemical phenomena in the environment.
12 Principles of green chemistry
Paul Anastas Green Chemistry at Yale , then of the EPA and John C. Warner developed 12 principles of green chemistry, which help to explain what the definition means in practice. The principles cover such concepts as:
- the design of processes to maximize the amount of raw material that ends up in the product
- the use of safe, environment-benign substances, including solvents, whenever possible
- the design of energy efficient processes
- the best form of waste disposal: do not to create it in the first place.
The 12 principles
- It is better to prevent waste than to treat or clean up waste after it is formed.
- Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
- Wherever practicable, synthetic methodologies should be designed to use and generate substances that process little or no toxicity to human health and the environment.
- Chemical products should be designed to preserve efficacy of function while reducing toxicity.
- The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and, innocuous when used.
- Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.
- A raw material of feedstock should be renewable rather than depleting wherever technically and economically practicable.
- Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.
- Catalysts (as selective as possible) are superior to reagents.
- Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products.
- Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
- Substances and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosion, and fires.
. Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice, Oxford University Press, Oxford, 1998.
Atom economy A nice lesson with examples
Green Chemistry Assistant
Developed by St.Olaf College, the green chemistry assistant helps you analyze chemical processes that you are interested in terms of Green Chemistry. But you will find, if you explore a little, that the Green Chemistry Assistant is useful far beyond the typical confines of that field.
How homogenous catalysis relates to green chemistry concepts?
The design of environmentally benign products and processes may be guided by the 12 principles of Green Chemistry. In this context catalysts should be used instead of reagents whenever possible. Catalytic reactions in general reduce energy requirements and decrease separations due to increased selectivity: they may also permit the use of renewable feedstocks and minimize the quantities of reagents needed. Transition metal catalysis has become one of the most important tools in organic synthesis. It has allowed entirely new transformations which were not possible previously by ‘traditional’ organic reactions and thus significantly increased the efficiency of synthesis. There is little doubt that the Nobel Prize-winning research by Sharpless, Noyori and Knowles (2001) and Chauvin, Grubbs and Schrock (2005) met many green chemistry goals.
Although the future challenges facing green chemistry are very broad and diverse there is a term that summarizes the solution to most of them: ‘benign by design’. This implies the conscious and deliberate use of a set of criteria, principles, and methodologies in the practice of green chemistry. In the area of homogeneous catalysis this implies a) the study of reaction mechanisms (to design more efficient and selective catalysts as well as increasing the knowledge of biological and environmental mechanisms of action) and b) the design of more environmentally friendly and less hazardous (ideally innocuous) catalysts.
. Borman, S. ‘Asymmetric Catalysis Wins’. Chem. Eng. News 2001, 79 (42) 5.
. Rouhi, A.M. ‘Olefin Metathesis Gets Nobel Nod’. Chem. Eng. News 2005, 83 (41) 8.
. Anastas, P.T.; Kirchoff, M.M. ‘Origins, current status, and future challenges of green chemistry’. Acc. Chem. Res. 2002, 35, 686
Gold as a greener catalyst?
In the last years gold has become one of the heterogeneous catalysts of choice for processes as important as hydrogenation and selective and total oxidation reactions. Gold heterogeneous catalysts have been found to address at least 8 of the 12 Green Chemistry Principles.
Gold has emerged in the last 5 years as a metal with an enormous potential in homogeneous catalysis due to its high activity and unprecedented selectivity in a variety of organic reactions while being a substitute for more toxic classical catalysts, such as mercury. It has been considered a ‘greener’ catalyst because very small amounts of it are needed but, also, on many of the catalytic reactions studied gold salts and compounds decompose to metallic gold (that may be easily separated and recovered from the final products). The apparent insensitivity of Au to aqueous conditions has allowed its use in several reactions using water or alcohols as ‘greener’ solvents.
. Hutchings, G.J. ‘A golden future for green chemistry’. Catal. Today, 2007, 122
. (a) Hashmi, A.S.K.; Hutchings, G.J. ‘Gold catalysis’. Angew. Chem. Int. Ed. 2006, 45, 78096. (b) Hashmi, A.S.K. ‘Gold-catalyzed organic reactions’. Chem. Rev. 2007, 107, 3180.
Links of interest
- Green Chemistry in Education Network
- Green Chemistry Educational Materials (University of Oregon)
- Green Chemistry Educational Materials
- Green Chemistry Institute (American Chemical Society)
- U.S. Environmental Protection Agency (Green Chemistry)
- Universities/Research Centres with Green Chemistry Programs in the US and overseas
- The Center for Green Chemistry at UMass Boston.
- Center for Green Chemistry and Green Engineering at Yale University)
- US and International Schools with green chemistry programs
- Map of individuals interested in Green Chemistry (Research and Education) around the world
- Green Chemistry (Journal published by the Royal Society of Chemistry)
- Overview page (continuously updated listing of recently reported organic synthetic methods). Organic Chemistry Portal. Reto Mueller (Germany)
- ACS Division of Environmental Chemistry
- Agency for Toxic Substances and Disease Registry
- Alliance for Global Sustainability
- Alternative Energy Sources
- ACS Education Section
- Canadian Centre for Pollution Prevention
- Canadian Green Chemistry Network
- Carolina Environmental Program
- Centre for Atmospheric Chemistry
- Centers for Disease Control/NIOSH
- Center for the Study of Carbon Dioxide and Global Change
- Center of Excellence for Sustainable Development
- Communication for a Sustainable Future
- Consortium on Green Design and Manufacturing
- The Current Step (Current sustainability Issues)
- Earth Vision Environmental Resources
- Education for Sustainability
- Energy Efficiency Renewable Energy Network
- Energy Saving Tips
- Environmental Chemistry & Hazard Information
- Environmental Careers Association
- Environmentally Friendly cars
- Environmental Policy (includes links to homepages from all levels of government)
- Environmental Yellow Pages
- EPA Green Chemistry (Industry)
- The Environmental Institute, Carnegie Mellon University
- The Environmental Site
- EPA Sustainability Website
- Gas and electric: understanding hybrid cars
- The Green Business Letter
- Green Chemistry Group (York)
- Green Chemistry Network
- Green Chemistry Resources
- "Getting Clean by Going Green"
- Inca Green Chemistry Site (Italy)
- Indigo Development
- Institute of Green Oxidation Chemistry
- Internet Resources for Green Chemistry
- Los Alamos National Laboratory
- National Defense Center for Environmental Excellence
- National Environmental Method Index (with greener analytical methods!)
- National Environmental Technology for Waste Prevention Institute
- National Pollution Prevention Roundtable
- Oak Ridge National Laboratory
- Office of Pollution Prevention and Toxics (EPA)
- Pacific Northwest National Laboratory
- Pollution Prevention Networks
- Recycling 101
- Royal Society Environmental Chemistry
- Sandia National Laboratory
- The Science Lab
- Soap and Detergent Association website
- Solvent Alternative Guide
- St.Olaf College (Green Chemistry)
- SUSTECH: Collaborative research in sustainable technologies for the process industries
- Syracuse Research Corporation Environmental Science
- Tellus Institute
- Toxic Substances and Disease Registry (ATSDR)
- Toxics Use Reduction Institute
- University of Massachusetts (Boston)
- United Nations Industrial Development Organization
- Zero Waste Alliance
More links of interest (Green Chemistry and Sustainability) in alphabetical order: