2.4.7 Green Chemistry Describe principles and discuss issues of chemical sustainability. Understand the importance of establishing international cooperation to promote the reduction of pollution levels CO 2 – villain to saviour Discuss some of the ways of reducing CO 2 emissions into the environment. Outline some of the positive benefits of using CO 2 as a substitute for more harmful materials.

GREEN CHEMISTRY What is it? encourages environmentally conscious behaviour reduces and prevents pollution reduces the destruction of the planet

GREEN CHEMISTRY What is it? encourages environmentally conscious behaviour reduces and prevents pollution reduces the destruction of the planet Basics better to prevent waste than to treat it afterwards aim for maximum atom economy use processes which require fewer chemicals don’t make products that are toxic to human health don’t make products that are toxic to the environment reduce the energy requirements of processes use alternative energy resources use renewable raw materials, not finite resources use catalysts where possible waste products should be designed to be biodegradable reduce the risk of explosions and fires

RECYCLING Definition“Recovering resources by collecting, separating, and processing scrap materials and using them as raw materials for manufacturing new products.”

RECYCLING Definition“Recovering resources by collecting, separating, and processing scrap materials and using them as raw materials for manufacturing new products.” Why do it? world resources are running out and are non-renewable we need to reduce the waste of valuable resources reduces the expense of disposal reduces expense of making things from raw materials avoids environmental problems posed by waste - landfill sites - greenhouse gases (mainly methane) - destroying habitats - de-forestation leading to climate change and the destruction of ecosystems

RENEWABLE RESOURCES AND ENERGY

Renewable resources can be replenished by natural processes their rate of replenishment is equal or greater than the rate of consumption often do not contribute to global warming often far more environmentally friendly lead to more sustainable use of materials; resources can be used indefinitely

RENEWABLE RESOURCES AND ENERGY Renewable resources can be replenished by natural processes their rate of replenishment is equal or greater than the rate of consumption often do not contribute to global warming often far more environmentally friendly lead to more sustainable use of materials; resources can be used indefinitely Renewable energy plant-based substances such as wood solar energy tidal energy biomass hydro-electric power (HEP) wind power

GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects.

GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD created in 1928 as a non-toxic, non-flammable refrigerant also used as solvents and in air conditioners low reactivity and volatility

GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD created in 1928 as a non-toxic, non-flammable refrigerant also used as solvents and in air conditioners low reactivity and volatility BAD UV light in the upper atmosphere easily breaks the C-C l bonds free radicals formed speeded up the depletion of the ozone layer

GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD created in 1928 as a non-toxic, non-flammable refrigerant also used as solvents and in air conditioners low reactivity and volatility BAD UV light in the upper atmosphere easily breaks the C-C l bonds free radicals formed speeded up the depletion of the ozone layer CFC's break down in the presence of UV light to form chlorine radicalsCC l 2 F 2 —> C l + CC l F 2 chlorine radicals react with ozoneO 3 + C l —> C l O + O 2 chlorine radicals are regeneratedC l O + O —> O 2 + C l Overall, chlorine radicals are not used up so a small amount of CFC's can destroy thousands of ozone molecules before the termination stage.

GREEN CHEMISTRY – EXAMPLES CFC’s Apparent benefits were offset by unexpected side effects. GOOD created in 1928 as a non-toxic, non-flammable refrigerant also used as solvents and in air conditioners low reactivity and volatility BAD UV light in the upper atmosphere easily breaks the C-C l bonds free radicals formed speeded up the depletion of the ozone layer CFC's break down in the presence of UV light to form chlorine radicalsCC l 2 F 2 —> C l + CC l F 2 chlorine radicals react with ozoneO 3 + C l —> C l O + O 2 chlorine radicals are regeneratedC l O + O —> O 2 + C l Overall, chlorine radicals are not used up so a small amount of CFC's can destroy thousands of ozone molecules before the termination stage.

GREEN CHEMISTRY – EXAMPLES BIOFUELS fuels made from a living things or the waste produced by them renewable and potentially carbon neutral.

GREEN CHEMISTRY – EXAMPLES BIOFUELS fuels made from a living things or the waste produced by them renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel.

GREEN CHEMISTRY – EXAMPLES BIOFUELS fuels made from a living things or the waste produced by them renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel.ETHANOL GOOD

GREEN CHEMISTRY – EXAMPLES BIOFUELS fuels made from a living things or the waste produced by them renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel.ETHANOL GOOD bio-ethanol is made from crops (corn and sugar cane) takes in carbon as carbon dioxide in the atmosphere when burnt, it returns CO 2 to the atmosphere appears to be carbon neutral

GREEN CHEMISTRY – EXAMPLES BIOFUELS fuels made from a living things or the waste produced by them renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel.ETHANOL GOOD bio-ethanol is made from crops (corn and sugar cane) takes in carbon as carbon dioxide in the atmosphere when burnt, it returns CO 2 to the atmosphere appears to be carbon neutral BAD

GREEN CHEMISTRY – EXAMPLES BIOFUELS fuels made from a living things or the waste produced by them renewable and potentially carbon neutral. Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel.ETHANOL GOOD bio-ethanol is made from crops (corn and sugar cane) takes in carbon as carbon dioxide in the atmosphere when burnt, it returns CO 2 to the atmosphere appears to be carbon neutral BAD energy is required to - plant and harvest - convert plants to ethanol fertiliser and pesticides used are pollutants crops compete for land with… crops / animals / forests could destroy natural habitats and reduce biodiversity

GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier.

GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD

GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD many are chemically inert non-toxic waterproof easy to mould non-biodegradable lightweight

GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD many are chemically inert non-toxic waterproof easy to mould non-biodegradable lightweight BAD

GREEN CHEMISTRY – EXAMPLES PLASTICS & POLYMERS Plastics have made life much easier. GOOD many are chemically inert non-toxic waterproof easy to mould non-biodegradable lightweight BAD made from crude oil which is a finite resource non-biodegradable so take hundreds of years to decompose can form toxic products during incineration a lot of energy is used in their formation disposal in landfill sites is- a waste of resources - environmentally unsound - takes up valuable space

GREEN CHEMISTRY – EXAMPLES CATALYSTS can be used to lower the energy required for a reaction to take place can reduce the CO 2 emissions from burning of fossil fuels can give a better atom economy

CO 2 – villain to savior Using CO 2 - super critical fluid CO 2CO 2 in foams CO 2CO 2 as a solvent CO 2CO 2 extraction of caffeine in coffee CO 2CO 2 for beer CO 2CO 2 for dry cleaning CO 2CO 2 toxic waste treatment CO 2CO 2 for chemical synthesis

2.4.7 Green Chemistry Pages The 12 Principles Questions 1 – a & b CO 2 – villain to saviour ! Questions 1 & 2

Exam Questions Page 238 – 239 Homework : Q 1, 2, 3 By Monday

THE TWELVE PRINCIPLES OF GREEN CHEMISTRY 1. It is better to prevent waste than to treat or clean up waste after it is formed. 2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product. 3. Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment. 4. Chemical products should be designed to preserve efficacy of function while reducing toxicity.

5. The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary whenever possible and, innocuous when used. 6. 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. 7. A raw material feedstock should be renewable rather than depleting whenever technically and economically practical. 8. Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.

9. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. 10. 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. 11. 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. Substances and the form of a substance used in a chemical process should chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires.