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Green chemistry

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Introduction to the concept of Green Chemistry and why is it a viable option to switch into.

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Green chemistry

  1. 1. A PROJECT BY:- MOINAK SARKAR NILAY JOSHI PUSHTY TALATI PRADYUT TALUKDAR Class XI-B…
  2. 2. Definition-“The design of chemical products and processes that are more environmentally friendly and reduce negative impacts to human health and the environment.” Green chemistry looks at pollution prevention on the molecular scale 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. 3. The concept of green chemistry was formally established at the ENVIRONMENTAL PROTECTION AGENCY 25 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. Though it is said that the concept was originated by Trevor Kletz in his 1978 paper where he proposed that chemists should seek alternative processes to those involving more dangerous substances and conditions.
  4. 4. 4 Green Chemistry Is About Waste Material Hazard Risk Energy Cost
  5. 5. Prevent Waste Maximize Atom Economy Less Hazardous Chemical Syntheses Safer Chemical and Products Safer solvent and reaction conditions Increase Energy Efficiency Use renewable Feedstock Avoid Chemical Derivatives Use catalysts Design chemical and products to degrade after use Analyze in real time to prevent pollution Minimize Potential for accidents
  6. 6.  1.Prevention:  “It is better to prevent waste than to treat or clean up waste after it is formed.”  It is advantageous to carry out a synthesis in such a way that the formation of waste products is minimum or absent. The waste if discharged in the atmosphere, sea and land causes not only pollution but also requires expenditure for cleaning up.
  7. 7.  Some dreadful examples of ill effects from untreated waste disposal:  1.Love Canal:  In Niagara Falls, NY a chemical and plastics company had used an old canal bed as a chemical dump from 1930s to 1950s. The land was then used for a new school and housing track. The chemicals leaked through a clay cap that sealed the dump. It was contaminated with at least 82 chemicals (benzene, chlorinated hydrocarbons, dioxin). Health effects of the people living there included: high birth defect incidence and seizure-inducing nervous disease among the children.
  8. 8.  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: (actual yield/theoretical yield) * 100 Atomic Economy: (%AE)=(FW of atoms utilized/FW of all reactants) * 100
  9. 9.  3.Less Hazardous Chemical Synthesis “Wherever practicable,  synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment.”  Example of an unsafe drug is THALIDOMIDE for lessening the effect of nausea and vomiting during pregnancy. The child born to women taking the drug suffers from birth defects like deformed- limbs.
  10. 10.  4.Designing Safer Chemicals  “Chemical products should be designed to preserve efficacy of function while reducing toxicity.”  •Synthetic methodologies should be designed to generate substances that generate substances that possess less harmful or toxic products.  •This principle focuses on choosing reagents that pose the least risk and generate only safe by- products.  •For example: in the manufacture of Polystyrene, CFC’s which contribute to ozone depletion and global warming are replaced by CO2.
  11. 11.  5.Safer Solvents and Auxiliaries  “The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.”  •The solvent selected for a particular reaction shouldn't cause any environmental pollution or hazard (e.g. benzene, alcohol).  •One major problem with many solvents is their volatility that may damage environment and human health.  •To avoid this many reactions are carried out in safer green solvents like ionic liquids, supercritical CO2fluid etc. which maintain the solvency of the material and are also non-volatile.
  12. 12.  6.Design for Energy Efficiency  “Energy requirements should be recognized 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:  1) If the starting material is soluble in the particular solvent, the reaction mixture has to be heated till the reaction is complete.  2) If the final product is impure it has to be purified by distillation or recrystallization .  All these steps involve the use of high amount of energy which is uneconomical
  13. 13. 7.USE OF RENEWABLE FEEDSTOCKS  “A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable.”  Renewable feedstock are often made from agricultural products or are the wastes of other processes ; depleting feedstock are made from fossil fuels ( petroleum , natural gas or coal) or are mined .  For example :  Substances like CO2 ( generated from natural sources )  And methane gas are considered as renewable starting materials.
  14. 14. 8. Reduce derivatives  Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate more waste . Two synthetic steps are added each time when one is used. Overall yield atom economy decrease .  Instead , more selective and better alternative synthetic sequences that eliminate the need for functional group protection should be adopted
  15. 15. 9.Catalysis  Use of a catalyst transformation without the catalyst being consumed in the reaction and without being incorporated in the final product .  Some advantages of catalyst are :  BETTER YIELDS  CH3-CH=CH2 + H2 CH3-CH2-CH3  ( propene ) ( propane)  The hydrogenation of olefins is carried out in the presence of nickel .
  16. 16. 10. Design for degradation  For example:  Sulfonated detergents :  Alkyl benzene sulfonates-1950s& 60s.  Foam in sewage plants, rivers and streams .  Persistence was due to long alkyl chain .  Introduction of alkene group into the chain increased degradation.  2. Chlorofluorocarbons ( CFCs )  Do not breakdown , persist in atmosphere and contribute to destruction of ozone layer
  17. 17.  3. DDT  Insecticides like DDT tend to bio- accumulate in many plant and animal species and incorporate into food chains resulting in population decline of beneficial insects and animals .
  18. 18. 11. REAL-TIME ANALYSIS FOR POLLUTION PREVENTION  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 !
  19. 19. 12. Inherently safer chemistry for accident prevention  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 an 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 . More than 120,000 still suffer from ailments caused by exposure .
  20. 20. BENEFITS OF GREEN CHEMISTRY  Human health:  Cleaner air: Less release of hazardous chemicals to air leading to less damage to lungs  Cleaner water: less release of hazardous chemical wastes to water leading to cleaner drinking and recreational water  Increased safety for workers in the chemical industry; less use of toxic materials; less personal protective equipment required; less potential for accidents (e.g., fires or explosions)
  21. 21.  Safer consumer products of all types: new, safer products will become available for purchase; some products (e.g., drugs) will be made with less waste; some products (i.e., pesticides, cleaning products) will be replacements for less safe products  Safer food: elimination of persistent toxic chemicals that can enter the food chain; safer pesticides that are toxic only to specific pests and degrade rapidly after use  Less exposure to such toxic chemicals as endocrine disruptors
  22. 22.  Environment:  Green chemicals either degrade to innocuous products or are recovered for further use.  Plants and animals suffer less harm from toxic chemicals in the environment.  Lower potential for global warming, ozone depletion, and smog formation.  Less chemical disruption of ecosystems.  Less use of landfills, especially hazardous waste landfills.
  23. 23. Economy and business:  Higher yields for chemical reactions, consuming smaller amounts of feedstock to obtain the same amount of product  Fewer synthetic steps, often allowing faster manufacturing of products, increasing plant capacity, and saving energy and water  Reduced waste, eliminating costly remediation, hazardous waste disposal, and end-of-the-pipe treatments  Increased consumer sale by earning and displaying a safer product label
  24. 24.  Reduced use of petroleum products, slowing their depletion and avoiding their hazards and price fluctuations  Reduced manufacturing plant size or footprint through increased throughput  Improved competitiveness of chemical manufacturers and their customers
  25. 25. Conclusion.. As Paul T. Anastas said that his dream is not that Green Chemistry is practiced by every person but rather whole Chemistry is Green. Remember:- Green chemistry is NOT a solution to all environmental problems BUT the most fundamental approach to preventing pollution.

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  • KulwinderRamgariah

    Nov. 26, 2019
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    Dec. 4, 2019
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    Jan. 21, 2020
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    Apr. 19, 2020

Introduction to the concept of Green Chemistry and why is it a viable option to switch into.

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