CH1 Green Chemistry_Feb2024.pdf

Green Chemistry Principles and Concepts of Green Chemistry Delivery Plan CH1 Principle and Concept of Green Chemistry CH2 Waste Production problem and prevention CH3 Catalysis and green chemistry CH4 Renewable Energy CH5 Green Solvents: Environmentally Benign Solutions 2/18/2024...

Green Chemistry Principles and Concepts of Green Chemistry Delivery Plan CH1 Principle and Concept of Green Chemistry CH2 Waste Production problem and prevention CH3 Catalysis and green chemistry CH4 Renewable Energy CH5 Green Solvents: Environmentally Benign Solutions 2/18/2024 Prepared By: 2 Our life now and Chemistry Name for me one product that has no chemistry in it Transportation Clothing Sport Food Safety Medical Home/farm 2/18/2024 Prepared By: KAB 3  Downside of Chemistry & Chemical Industry Pollutants Toxic substances Non-biodegradable plastics 2/18/2024 Prepared By: 4 Sustainable development Sustainable development based on the United Nations Commission on the Environment and Development (1987) “ meeting the needs of the present without compromising the ability of future generation to meet their own need” 2/18/2024 Prepared By: 5 Sustainable development The Natural Step ( an international movement started in Sweden) dedicated to helping Society to reduce their impact on environment The Natural step 4 system conditions for sustainability 1. Materials from the Earth’s crust (e.g. heavy metals) must not systematically increase in nature. 2. Persistent substances produced by society (e.g. DDT, CFCs) must not systematically increase. 3. The physical basis for the Earth’s productive natural cycles must not be systematically deteriorated. 4. There must be fair and efficient use of resources with respect to meeting human needs. 2/18/2024 Prepared By: 6 Circular Economy vs Linear Economy A circular economy is a strategy aimed at optimizing resources used within industries. It involves a model of production and consumption in which recycling, sharing, leasing, and refurbishing of existing materials are performed for as long as possible. 2/18/2024 Prepared By: Image courtsey: World Economic forum 7 Circular Economy vs Linear Economy When industries use raw materials to create a product, use product and dispose product 2/18/2024 Prepared By: 8 History of Green Chemistry Love Canal incident in Niagara Falls (22,000 tons Rachel Carson wrote the of chemical waste The Pollution Prevention Act of mainstream, (including 1990 marked a regulatory policy scientific book, Silent polychlorinated biphenyls, change from pollution Spring dioxin, and pesticides) control to pollution prevention 1970 1988 Early 1990s 1962 Late 1970s 1990 President Richard Nixon Office of Pollution European Community's established the U.S. Prevention and Toxics was Chemistry Council Environmental Protection established within the EPA published papers including Agency (EPA) facilitate these the subject, "Chemistry for environmental goals. a Clean World 2/18/2024 Prepared By: 9 History of Green Chemistry Paul Anastas and John C. Warner co-authored The first symposium based on these ideas, the groundbreaking book, Green Chemistry: "Benign by Design: Alternative Synthetic Design Theory and Practice in 1998. The 12 Principles for Pollution Prevention" was held Chicago of Green Chemistry 1994 1998 Staff of the EPA Office of Pollution Prevention and Toxins, coined the phrase "Green Chemistry" and sowed the seeds of productive collaboration between government, industry, and academia. Motivated scientists Guide green chemistry movement 2/18/2024 Prepared By: 10 Green Chemistry Green chemistry seeks to present a body of chemical knowledge from the most fundamental level within a framework of the relationship of chemical science to human being , their surrounding and their environment Green Chemistry is the practice of chemistry in manner that maximize its benefit while eliminating or at least greatly reducing its adverse impact Green Chemistry based on US environmental protection agency (EPA) “ to promote innovative chemical technology that reduce or eliminate the use or generation of hazardous substances in the design, manufacture and use of chemical products 2/18/2024 Prepared By: 11 Green Chemistry The design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, use, and ultimate disposal. Prevents pollution at the molecular level o Results in source reduction because it prevents the generation of pollution Is a philosophy that applies to all areas of chemistry, not a single discipline of chemistry Applies innovative scientific solutions to real-world environmental problems Reduces the negative impacts of chemical products and processes on human health and the environment Lessens and sometimes eliminates hazard from existing products and processes Designs chemical products and processes to reduce their intrinsic hazards 2/18/2024 Prepared By: 12 Typical Chemical Manufacturing Process React to form an Start with a petroleum- Dissolve in a solvent Add reagent intermediate chemical based feedstock based Repeat step 2-4 until product obtained Release the product into the ecosystem Transport the product Discarded all waste and without evaluation of its long term effect world wide spent reagent, recycle 2/18/2024 Prepared By: solvent 13 Sustainable Chemical Manufacturing Process Design the molecule to have minimal impact on the environment (short residence time , biodegradable) Manufacturing from a renewable feedstock Using a long-life catalyst Use no solvent or totally benign solvent Use the smallest possible number in the synthesis Manufacture the products as required and close as possible to where its required 2/18/2024 Prepared By: 14 The 12 Principles of Green Chemistry 2/18/2024 Prepared By: 15 The 12 Principles of Green Chemistry 1 Prevention of pollution It is better to prevent waste than to clean up waste after it formed 2 Atom Economy Synthetic methods to be designed to maximize the use of all materials in the process to the final product 3. Less Hazardous chemical synthesis Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment 2/18/2024 Prepared By: 16 The 12 Principles of Green Chemistry (continued.. 4. Designing safer chemicals Chemical products should be designed to preserve efficacy of function while reducing toxicity 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 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 2/18/2024 Prepared By: 17 The 12 Principles of Green Chemistry (continued..) 7. Use of Renewable Feedstocks A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable. 8. Reduce Derivatives Unnecessary derivatization (use of blocking groups, protection/deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste. 9. Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents 2/18/2024 Prepared By: 18 The 12 Principles of Green Chemistry (continued..) 10. Design for Degradation Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment. 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. 12. Inherently Safer Chemistry for Accident Prevention Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires 2/18/2024 Prepared By: 19 Atom Economy Typical reaction with less than 100% yield and with byproduct Reaction with 100% yield but with by product inherent to the reaction Reaction with 100% atom economy, no leftover reactants , no byproducts 2/18/2024 Prepared By: 20 Atom Economy Atom economy is a measure of how many atoms of reactants end up in the final product and how many end up in byproducts or waste. X+Y P+U Disregards substances, such as solvents and chemicals used in the work-up of the reaction mixture, which do not appear in the stoichiometric equation Measure of reaction efficiency actual quantity of products achieved % 𝑦𝑖𝑒𝑙𝑑 = 100 × theoretical quantity of products achievable yield of desired product % 𝑆𝑒𝑙𝑒𝑐𝑡𝑖𝑣𝑖𝑡𝑦 = 100 × amount of substrate converted Relative molecular mass desired products % 𝐴𝑡𝑜𝑚 𝐸𝑐𝑜𝑛𝑜𝑚𝑦 = 100 × Relative molecular mass of all reactants 2/18/2024 Prepared By: 21 Atom Economy A theoretical way to measure what percent of atom/mass from your reactant end up in your desired product Ideally all your atoms/mass end up in the desired product and no atoms end up as waste 2/18/2024 Prepared By: 22 Atom Economy 2/18/2024 Prepared By: 23  Atom Economy : Atom Economic Reactions Rearrangement Reaction: Exception: ‘catalyzed’ by stoichiometric amounts of a Lewis acid such as AlCl3. Large amount of ‘catalyst’ is due to it complexing with the product; work-up with water hydrolyses the complex producing copious amounts of aluminium waste. Reduces the atom economy of the reaction as the AlCl3 should be considered a reagent rather than Green alternative: Photo Fries Rearrangement a catalyst since it is not recovered in a reusable 2/18/2024 form. Prepared By: 24 Atom Economy : Atom Economic Reactions: 2/18/2024 Prepared By: 25 Atom Economic Reactions: Addition reaction Electrophilic Addition A R AB R R R B Michael Addition 2/18/2024 Prepared By: 26 Atom uneconomic reaction Substitution Reactions 2/18/2024 Prepared By: 27 Atom uneconomic reaction Elimination Reactions Atom uneconomic reaction Elimination Reactions E factor Mass ratio of waste to desired product and the atom efficiency E factor is actual amount of waste produced in the process everything but the desired product It takes chemical yield into account and include reagents, solvents losses ,all process aids A higher E factor means more waste and greater environmental impact E factor=kg waste/Kg of products out 2/18/2024 Prepared By: 30 E factor Notes on the E-factor an experiment must be performed Must keep track of all inputs used to make the products Reactants including catalyst Account for Need to Amount of solvent for reaction all waste actually Amount of solvent for recrystallization including perform a solvents and reaction Mass of weight paper auxiliaries Water used for washing Silica for the column …etc Can compare Ignore type of how wasteful waste if your hazardous procedures or/and are biodegradable 2/18/2024 Prepared By: 31 Difference between Atom Economy & E-factor E-Factor takes the product yield into account and waste from all of the auxiliary components, e.g. solvent losses, chemicals used in work-up, which are disregarded by AE. Second, AE is applied to individual steps but the E factor can easily be applied to a multi-step process thus facilitating a holistic assessment of a complete process. A higher E factor means more waste and greater negative environmental impact. 2/18/2024 Prepared By: 32 E-factor for chemical industries If E-factor is 2, it means you produce twice as much as waste as product An E-factor of 0.1 means it means you produce 10X product as much product as waste 2/18/2024 Prepared By: 33 E-factor Calculation Mass of total Materials Mass of product E factor used E factor =g waste /g product E factor =313.45/2.21=141.8 2/18/2024 Prepared By: 34 Reducing Toxicity Green Principle: Reduce (use and produce) hazardous materials Hazardous substances: toxicity, flammability, explosion potential, environmental persistence Lack of knowledge of toxicity In the past , knowledge after events/incindent (ill health or death) (via trial and error e.g nickel carbonyl (Highly toxic) used to produce nickel 2/18/2024 Prepared By: 35 Reducing Toxicity Natural Philosophy: Limit exposure to toxic chemical Hazard : A Risk : Probability situation that can that will occur lead to harm Risk= (Function) Hazard x Exposure Traditional approach: reduce risk by limiting exposure (through physical means via system and prudent practice Alternative approach: green chemistry to reduce hazard ( based on what you don’t have can’t harm you) COSHH (Control of substances Hazardous to Health) regulations require that assessments be made of all laboratory 2/18/2024 Prepared By: 36 and production work where potentially harmful chemicals are used Reducing Toxicity : Example Case: C–C bond formation via free radical chemistry (pharmaceutical companies) Traditional Approach: Free radicals produced through organotin compounds such as Bu4SnH which is an excellent radical chain carrier. Drawback: Organotin compounds are highly neurotoxic, Bu4SnH possess hazard, trace amount left product( not acceptable for product that are destined for human consumption) Green Alternative: oxidized sulfide that can produce required organic radical 2/18/2024 Prepared By: 37 Reducing Toxicity : Measuring Toxicity LD50 and LC50 LD Lethal Dose LC: Lethal concentration LD50: The dose of a chemical at which 50% of a group of animal are killed Unit: mg/Kg Carried out by injection or given orally a known dose of a pure chemical LC50: The concentration in air or water of the chemical that kills 50% of the test animals. Usually allowing an animal to breath a known concertation of chemical in air Units ppm or mg/m3 Such toxicity tests help develop Material Safety Data Sheets (MSDS) and establish Occupational Exposure Limits The lower LD50 and LC50 the more toxic the chemical is 2/18/2024 Prepared By: 38 Reducing Toxicity : Measuring Toxicity Ames Test (Named after its inventor, Bruce Ames) : Common screening tests for measuring the potential carcinogenic effects of chemicals. Based on observation of mutation from the bacterium Salmonella tryphimurium carrying a defective gene thus unable to synthesis histidine from ingredients of a culture medium If a chemical is mutagenic (Carcinogenic) it will cause mutation in the bacterium (histidine synthesis possible) Direct observation of population growth of bacteria resulting from the mutation is possible 2/18/2024 Prepared By: 39