Green synthesis environmental impact

Handbook of Green Chemistry and Technology, J. H. Clark and D. J. Macquarrie, Eds., Blackwell Publishing 2002, 540 pp., ISBN 0-632-05715-7. This collection of 22 review essays covers all the important areas of green chemistry, including environmental impact and life-cycle analysis, waste minimization, catalysts and their industrial applications, new synthesis methods, dean energy, and novel solvent systems. The chapters are well referenced and contain pertinent examples and case studies. 

Synthetic polymers are arguably the most important materials made by chemists and used in modem society. Chapter 30 Synthetic Polymers expands on the foundations of polymers discussed in earlier Chapters 15 and 22. Of significance is emphasis on the environmental impact of polymer synthesis and use, discussed in sections on Green Polymer Synthesis (30.8), Polymer Recycling and Disposal (Section 30.9A), and Biodegradable Polymers (Section 30.9B). 

This account provides a summary of a chapter on Microwave Irradiation for Accelerating Organic Reactions in Advances in Heterocyclic Chemistry, volume 90, Part II Six, Seven-membered, Spiro and Fused Heterocycles by E. S. H. El Ashry, A. A. Kassem and E. Ramadan. Microwave irradiation (MWI) has been used extensively in organic synthesis. Application of MWI leads to many advantages, like the use of non-corrosive and inexpensive reagents, in addition to the eco-friendly "green chemistry" economical and environmental impacts. 

The foregoing examples of phosgene-free methods for synthesis of carbamates, isocyanates, ureas, polycarbonates, dyes, polymers, and other pharmaceutical or agrochemical intermediates and products all illustrate ways that green chemistry reduces the environmental impact... 

Feedstock selection largely dictates the reactions and conditions that are employed in a chemical synthesis and is, therefore, of utmost importance in the practice of green chemistry. A feedstock should be as safe as possible. The source of a feedstock can largely determine its environmental impact, and the acquisition of the feedstock should not strain Earth s resources. The process of isolating and concentrating a feedstock can add to the potential harm of otherwise safe materials. This is true of some metal ores in which corrosive and toxic reagents (in the case of gold, e.g., cyanide see Section 16.4) are used to isolate the desired material. 

One of the key principles of green chemistry is the elimination of solvents in chemical synthesis or the replacement of hazardous solvents with environmentally benign solvents. The development of solvent-free alternative syntheses is, of course, the best solution, especially when either one of the substrates or the product is a liquid and can be used as the natural solvent of the reaction. However, if solvents are crucial to a process, we can select from solvents that will have no or limited impact on health and the environment and the selection should be an intrinsic part of green innovation. The most important rule is that we should match the solvent properties with the synthesis objectives and then identify the best available solvent or design a new solvent. 

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