Presentation.pptx. Green Chemistry and principal of green Chemistry​

A complete and comprehensive approach towards green chemistry & its applications. it plays significance role to sustain user friendly environment by reducing waste and enhance energy efficiency & atom economy. It leads less hazardous chemicals that are easy to discard.

1. Assignment #1 Green Chemistry and principles of G reen Chemistry Hajira Mahmood Ph.D. CHEMISTRY

2. Green chemistry An area of chemistry and chemical engineering that focus on the design of products and processing that eliminate or minimize the use of and generation of hazardous substances. The design of chemical processes and products to reduce or to eliminate the use and generation of toxic, poisonous, hazardous and bio-accumulative chemical substances, that are more environmental friendly and reduce negative impacts to human health and to the environment. A new scientific approach based on Environment Protection, plays vital role in controlling global warming, acid rain and climate change, and is an extremely important area of Chemistry due to the importance of Chemistry in our world today and the implications it can show on our environment.  The Green Chemistry program supports the invention of more environmentally friendly chemical processes which reduce or even eliminate the generation of hazardous substances

3. Father of Green Chemistry The concept of green chemistry was formally established at the ENVIRONMENTAL PROTECTION AGENCY 15 years ago, in response to the Pollution Prevention Act of 1990. Paul T. Anastas for the first time in 1991 coined the term Green Chemistry.

4. Principles of Green Chemistry Real-time Analysis for Pollution Prevention  Design for Degradation Catalysis Reduce Derivatives Design for energy efficiency.  Use of Renewable Feedstocks Waste Prevention  Less hazardous synthesis Designing Safer Chemicals Safer Solvents and Auxiliaries  Design for Energy Efficiency Atom Economy.

5. 1. Waste prevention  It is better to prevent waste formation than to treat or clean it after its formation. beneficial to carry out a synthesis in such a way that the formation of waste products is minimum or absent.  If wastes are discharged into the atmosphere, seas and to land, it would cause not only pollution, but expenditure would also be needed for cleaning up.

6. Waste Prevention 

7. 2. Atom Economy “Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.” • A synthesis is Perfectly Efficient or Atom Economical if it generates significant amount of waste which is not visible in percentage yield calculation. • Percent yield:   % Yield = actual yield / theoretical yield × 𝟏𝟎𝟎  •Atom Economy: % AE = 𝑭𝑾 𝒐𝒇 𝒂𝒕𝒐𝒎𝒔 𝒖𝒕𝒊𝒍𝒊𝒔𝒆𝒅 /𝑭𝑾 𝒐𝒇 𝒂𝒍𝒍 𝒓𝒆𝒂𝒄𝒕𝒂𝒏𝒕𝒔 × 𝟏𝟎𝟎 

8. Atom Economy Addition and Rearrangement  reactions are 100% atom economical reactions as all the reactants are incorporated into products. While S ubstitution and Elimination reactions are less atom economical. Atom economical reaction In Propene-propane reaction 64.8% reactants are incorporated into product as it takes place in presence of Nickel.   1. H3C-CH=CH2 + H2                        H3C-CH2-CH3   less atom economical the % atom economy is 36.5% 2. CH3(CH2)4CH2OH +SOCl2                        SO2 + CH3(CH2)4CH2Cl  

9. 3. Less hazardous synthesis

10. 4. Designing Safer Chemicals

11. 5. Safer Solvents and Auxiliaries 

12. Solvent selection  

13. 6. Design for Energy Efficiency “it is important to recognize energy requirements for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.”  In any chemical synthesis the energy requirement should be kept low for example:   If the starting material is soluble in a particular solvent, the reaction mixture must be heated till the reaction is complete.  If the final product is impure, it must be purified by the process of distillation or recrystallization .  All these steps involve the use of high amount of energy which is uneconomical.

14. 7. Use of Renewable Feedstocks  “ A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable.”  •Renewable feedstocks are the wastes of other processes and are often made from agricultural products.  depleting  Feedstocks that comprises petroleum, coal or natural gas are depleted from fossil fuels or are mined. • For example :- Substances like CO2 generated from natural sources and methane gas  are considered as renewable starting materials.

15. Use of Renewable Feedstocks 

16. 8. Reduce Derivatives “ Unnecessary derivatization such as blocking groups, protection/deprotection, temporary modification of physical or chemical processes should be minimized or if possible, avoid.”  This is necessarily important to overcome such steps because they required additional reagents and can generate waste. Overall yield and atom economy decrease.  Instead, more selective and better alternative synthetic sequences that eliminate the need for functional group protection should be adopted.

17. 9. Catalysis  “Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.” Use of a catalyst facilitates transformation without the catalyst being consumed in the reaction and without being incorporated in the final product.   Advantages   1. Better yields H3C-CH=CH2 + H2 H3C-CH2-CH3 Propene Propane the hydrogenation of olefins is carried out in presence of nickel.  2. The reaction becomes feasible in those cases where no reaction is normally possible.  3. Better utilization of starting material and minimum waste product formation.  

18. 10. Design for Degradation Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products.”  For example Sulfonated detergents  Long Alkylbenzene sulfonates – 1950’s & 60’s  Foam in sewage plants, rivers and streams Persistence was due to  alkyl chain  Introduction of alkene group into the chain increased degradation   Chlorofluorocarbons (CFCs)    Do not break down, persist in atmosphere and contribute to destruction of ozone layer   Insecticides like DDT tend to bio- accumulate in many plant and animal species and incorporate into the food chain resulting in population decline of beneficial insects and animals.

19. 11. Real-time Analysis for Pollution Prevention   “Analytical methodologies need to be further developed to allow for real- time, in-process monitoring and control prior to the formation of hazardous substances.” Real time analysis for a chemist is the process of “checking the progress of chemical reactions as it happens.” Knowing when your product is “done” can save a lot of waste, time and energy.

20. 12. Inherently Safer Chemistry for Accident Prevention “Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions, and fires.”  Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires and releases to the environment.  Example of such incident due to lack of such measures:-  December 3, 1984 – poison gas leaked from a Union Carbide factory, killing thousands instantly and injuring many more (many of who died later of exposure). Up to 20,000 people have died as a result of exposure (3-8,000 instantly). More than 120,000 still suffer from ailments caused by exposur

21. Four paths defining inherently safer design

22. Merits of green synthesis Green synthesis” of nanoparticles makes use of  environmentally friendly, non-toxic and safe reagents .  Nanoparticles synthesized using biological techniques or green technology have diverse natures , with greater stability and appropriate dimensions since they are synthesized using a one-step procedure.