Give the principles of green chemistry.


 Principles of Green Chemistry 

Green chemistry is the approach in chemical sciences that efficiently uses renewable raw materials, eliminating waste and avoiding the use of toxic and hazardous reagents and solvents in the manufacture and application of chemical products. Green chemistry takes into account the environmental impact and seeks to prevent or lessen that impact through several key principles outlined below.

Definition of Green Chemistry: According to environmental protection  agency, green chemistry is defined as a chemistry that designs chemical products and processes that are harmless to the environment. Chemical products should be made in such a manner that they do not remain in the environment at the end of their application and broken down into components that are harmless to environment. 

History: The term green chemistry was first given by Poul .T. Anastas in 1991 in special program  launched  by  the  US  environmental  Protection  Agency  (EPA)  to  implement sustainable development in chemistry  ,chemical technology by industry ,academia  and government.  In  1995  the  annual  US  presidential  green  chemistry  challenge  was announced. In 1996 the working party on green chemistry was created, acting within the framework of International Union  of Pure  and Applied Chemistry.  The first  book and journals on the subject of green chemistry were introduced in 1990 by the royal society of chemistry. Green chemistry includes  a  new approach to  the  synthesis,  processing and application  of  chemical  substances  in such a manner to reduce scourge to health and environment like: 

    • Clean Chemistry 
    • Atom Economy 
    • Environmentally benign chemistry. 

Twelve principles of Green chemistry have been developed by Poul Anastas, speaks about the  reduction  of  dangerous  or  harmful  substances  from  the  synthesis,  production  and application of chemical products. When designing a green chemistry process it is impossible to  meet  the requirements of all twelve principles  of the process at the  same time,  but it attempts to apply as many principles during certain stages of synthesis.

Prevention. It is better to prevent waste formation than to treat it after it is formed.

Atom economy. Design synthetic methods to maximize incorporation of all material used into final product.

Less hazard. Synthetic methods should, where practicable, use or generate materials of low human toxicity and environmental impact.

Safer chemicals. Chemical product design should preserve efficacy whilst reducing toxicity.

Safer solvents. Avoid auxiliary materials - solvents, extractants - if possible, or otherwise make them innocuous.

Energy efficiency. Energy requirements should be minimized: conduct synthesis at ambient temperature and pressure.

Renewable feedstocks. Raw materials should, where practicable, be renewable.

Reduce derivatives. Unnecessary derivatization should be avoided where possible.

Smart catalysis. Selectively catalyzed processes are superior to stoichiometric processes.

Degradable design. Chemical products should be designed to be degradable to innocuous products when disposed of and not be environmentally persistent.

Real-time analysis for pollution prevention. Monitor processes in real time to avoid excursions leading to the formation of hazardous materials.

Hazard and accident prevention. Materials used in a chemical process should be chosen to minimize hazard and risk for chemical accidents, such as releases, explosions, and fires.

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