about green chemistry

1、About Green Chemistry1.What is green chemistry?Green chemistry, also called sustainable chemistry, is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances.1 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.

2、 This act helped create a modus operandi for dealing with pollution in an original and innovative way. It aims to avoid problems before they happen. As a chemical philosophy, green chemistry applies to organic chemistry, inorganic chemistry, biochemistry, analytical chemistry, and even physical chemistry. While green chemistry seems to focus on industrial applications, it does apply to any chemistry choice. Click chemistry is often cited as a style of chemical synthesis that is consistent with t

3、he goals of green chemistry. The focus is on minimizing the hazard and maximizing the efficiency of any chemical choice. It is distinct from environmental chemistry which focuses on chemical phenomena in the environment. In 2005 Ryoji Noyori identified three key developments in green chemistry: use of supercritical carbon dioxide as green solvent, aqueous hydrogen peroxide for clean oxidations and the use of hydrogen in asymmetric synthesis.2 Examples of applied green chemistry are supercritical

4、 water oxidation, on water reactions, and dry media reactions. Bioengineering is also seen as a promising technique for achieving green chemistry goals. A number of important process chemicals can be synthesized in engineered organisms, such as shikimate, a Tamiflu precursor which is fermented by Roche in bacteria. There is some debate as to whether green chemistry includes a consideration of economics, but by definition, if green chemistry is not applied, it cannot accomplish the reduction in t

5、he use or generation of hazardous substances.2. PrinciplesPaul Anastas, then of the United States Environmental Protection Agency, and John C. Warner developed 12 principles of green chemistry,3 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 efficien

6、t processes;the best form of waste disposal: not to create it in the first place. The 12 principles are: 1 Prevent waste: Design chemical syntheses to prevent waste, leaving no waste to treat or clean up. 2 Design safer chemicals and products: Design chemical products to be fully effective, yet have little or no toxicity. 3 Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to humans and the environment. 4 Use renewable feedstock:

7、 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. 5 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 a

8、re used in excess and work only once. 6 Avoid chemical derivatives: Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate waste. 7 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. 8 Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If

9、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. 9 Increase energy efficiency: Run chemical reactions at ambient temperature and pressure whenever possible. 10 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. 11 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. 12 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

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