Green chemistry, also called sustainable chemistry, is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize 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. 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 the 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 Ryōji 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 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.
The term green chemistry was coined by Paul Anastas in 1991.[3]
Contents |
Paul Anastas, then of the United States Environmental Protection Agency, and John C. Warner developed 12 principles of green chemistry,[4] which help to explain what the definition means in practice. The principles cover such concepts as:
The 12 principles are:
The Presidential Green Chemistry Challenge Awards[5] began in 1995 as an effort to recognize individuals and businesses for innovations in green chemistry. Typically five awards are given each year, one in each of five categories: Academic, Small Business, Greener Synthetic Pathways, Greener Reaction Conditions, and Designing Greener Chemicals. Nominations are accepted the prior year, and evaluated by an independent panel of chemists convened by the American Chemical Society. Through 2006, a total of 57 technologies have been recognized for the award, and over 1000 nominations have been submitted.
The Royal Australian Chemical Institute (RACI) presents Australia’s Green Chemistry Challenge Awards. This awards program is similar to that of the United States Environmental Protection Agency (EPA), although the RACI has included a category for green chemistry education as well as small business and academic or government.
The Canadian Green Chemistry Medal is an annual award given to an individual or group for promotion and development of green chemistry in Canada and internationally. The winner is presented with a citation recognizing the achievements together with a sculpture.[6]
Green Chemistry activities in Italy center around an inter-university consortium known as INCA. Beginning in 1999, the INCA has given three awards annually to industry for applications of green chemistry. The winners receive a plaque at the annual INCA meeting.[7]
In Japan, The Green & Sustainable Chemistry Network, formed in 1999, is an organization consisting of representatives from chemical manufacturers and researchers. In 2001, the organization began an awards program. GSC Awards are to be granted to individuals, groups or companies who greatly contributed to green chemistry through their research, development and their industrialization. The achievements are awarded by Ministers of related government agencies.[8]
In the United Kingdom, the Crystal Faraday Partnership, a non-profit group founded in 2001, awards businesses annually for incorporation of green chemistry. The Green Chemical Technology Awards have been given by Crystal Faraday since 2004; the awards were presented by the Royal Society of Chemistry prior to that time. The award is given only to a single researcher or business, while other notable entries are given recognition as well.[9]
The Nobel Prize Committee recognized the importance of green chemistry in 2005 by awarding Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock the Nobel Prize for Chemistry for "the development of the metathesis method in organic synthesis." The Nobel Prize Committee states, "this represents a great step forward for 'green chemistry', reducing potentially hazardous waste through smarter production. Metathesis is an example of how important basic science has been applied for the benefit of man, society and the environment."[10]
Attempts are being made not only to quantify the greenness of a chemical process but also to factor in other variables such as chemical yield, the price of reaction components, safety in handling chemicals, hardware demands, energy profile and ease of product workup and purification. In one quantitative study,[11] the reduction of nitrobenzene to aniline receives 64 points out of 100 marking it as an acceptable synthesis overall whereas a synthesis of an amide using HMDS is only described as adequate with a combined 32 points.
Green chemistry is increasingly seen as a powerful tool that researchers must use to evaluate the environmental impact of nanotechnology.[12] As nanomaterials are developed, the environmental and human health impacts of both the products themselves and the processes to make them must be considered to ensure their long-term economic viability.
In 2007, Europe put into place the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) program, which requires companies to provide data showing that their products are safe. This regulation (1907/2006) ensures not only the assessment of the chemicals' hazards as well as risks during their uses but also includes measures for banning or restricting/authorising uses of specific substances. ECHA, the EU Chemicals Agency in Helsinki, is implementing the regulation whereas the enforcement lies with the EU member states. The US Toxic Substances Control Act, passed in 1976, in principle has similar provisions but is not comparable to REACH as to its regulatory effectiveness.
On September 29, 2008 California approved two laws which encourage green chemistry, launching the California Green Chemistry Initiative. The law requires California's Department of Toxic Substances Control to prioritize "chemicals of concern", and puts the burden of testing on the agency rather than industry. The laws were criticized by Paul Anastas, who stated that the laws did not go far enough in encouraging research, education, and industry incentives.[13] The law called for regulations to be in place by January 1, 2011, but universal opposition to the previously proposed regulations rendered that date impossible. Mid October 2012 is the new target date for new draft regulations to be in place to implement the law. [14]
Research is currently ongoing in the area of supramolecular chemistry to develop reactions which can proceed in the solid state without the use of solvents. The cycloaddition of trans-1,2-bis(4-pyridyl)ethylene is directed by resorcinol in the solid state. This solid-state reaction proceeds in the presence of UV light in 100% yield.[15]
Research is currently also going in the area of natural product synthesis to develop reactions which can proceed involving green chemistry principles. Recently, Atul Kumar has developed an efficient and green method for the synthesis of tryptanthrin, a biologically active natural product, employing β-cyclodextrin as a catalyst in aqueous media at room temperature from isatoic anhydride and isatin in excellent yields.[16]
In March 2006, the University of California published a report by Dr. Michael P. Wilson and colleagues, Daniel A. Chia and Bryan C. Ehlers, on potential chemicals policy for the California Legislature entitled, Green Chemistry in California: A Framework for Leadership in Chemicals Policy and Innovation <http://coeh.berkeley.edu/news/06_wilson_policy.htm>. The report finds that long-standing weaknesses in the U.S. chemical management program, notably the Toxic Substances Control Act (TSCA) of 1976, have produced a chemicals market in the U.S. that discounts the hazardous properties of chemicals relative to their function, price, and performance. The report concludes that these market conditions represent a key barrier to the scientific, technical, and commercial success of green chemistry in the U.S., and that fundamental policy changes are needed to correct these weaknesses. Drs. Wilson and Schwarzman of UC Berkeley published their analysis in the August issue of Environmental Health Perspectives (EHP) in an article entitled, Toward a New U.S. Chemicals Policy: Rebuilding the Foundation to Advance New Science, Green Chemistry, and Environmental Health.[17]
The University of Massachusetts, Boston became the first university in the World to offer a Ph.D. in Green Chemistry.[18] In 2005, the University of Oregon's chemistry department unveiled the Greener Education Materials, a database of green chemistry topics.[19] In 2009, Oxford University Press/ACS Symposium Series published Green Chemistry Education: Changing the Course of Chemistry.[20] The book contains essays from a broad array of educators who share their best practices for the incorporation of green chemistry into the chemistry and chemical engineering curricula.
There are many green chemistry courses available in the UK at an MSc level. These include MSc in Green Chemistry & Sustainable Industrial Technology at the Green Chemistry Centre of Excellence based at the University of York, MSc Chemical Research in Green Chemistry at Leicester University and MRes in Green Chemistry at Imperial College London. A masters level course in Green Technology, has been introduced by the Institute of Chemical Technology, India in 2010. This is the first of its kind in India and aims at educating students about cleaner & more sustainable mechanisms for a greener tomorrow.
Several non-profit movements such as those of Ecology Center at Ann Arbor has moved to incorporate Green Chemistry into the curricula at local universities and highschools. [21]
Several laboratory chemicals are controversial, and alternatives have been explored. The Massachusetts Institute of Technology has created the Green Alternatives Wizard to help identify alternatives. Ethidium bromide, xylene, mercury, and formalin have been identified as "worst offenders" which have alternatives.[22] Solvents in particular make a large contribution to the environmental impact of chemical manufacturing and there is a growing focus on introducing Greener solvents into the earliest stage of development of these processes: laboratory-scale reaction and purification methods. In the Pharmaceutical Industry, both GSK[23][24] and Pfizer[25] have published Solvent Selection Guides for their Drug Discovery chemists.
Following historical analyses of the green chemistry development, there have been green chemistry advocates who see it as an innovative way of thinking. On the other hand, there have been chemists who have argued that green chemistry is no more than a public relations label. In fact, a lot of chemists use the term "green chemistry" independently from the green chemistry paradigm, as proposed by Anastas and Warner. This explains the uncertainty of the scientific status of green chemistry.[26]
|
|||||||||||||||||