Green Chemistry:

Cleaner,Cheaper, Safer, Greener!

 

Green Chemistry

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,[1] which help to explain what the definition means in practice. The principles cover such concepts as:

 

The 12 principles

 



[1]. 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)[2] and Chauvin, Grubbs and Schrock (2005)[3] met many green chemistry goals.
Although the future challenges facing green chemistry are very broad and diverse[4] 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.

 

[2]. Borman, S. ‘Asymmetric Catalysis Wins’. Chem. Eng. News 2001, 79 (42) 5.
[3]. Rouhi, A.M. ‘Olefin Metathesis Gets Nobel Nod’. Chem. Eng. News 2005, 83 (41) 8.
[4]. 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.[5]
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.

[5]. Hutchings, G.J. ‘A golden future for green chemistry’. Catal. Today, 2007, 122
[6]. (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.

 

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