KSEEB Class 11 Chemistry Notes For Green Chemistry
Chemistry is undeniably an important part of our lives since it leads to the formulation and fabrication of medicines, materials, polymers, paints, coatings, electronics etc. Chemists also address fundamental problems like global warming, ozone layer depletion, soil and water pollution, efficient food production via photosynthesis etc.
However, processes on an industrial scale not only produce the desired material, but also large quantities of undesired and toxic chemicals in the form of solids, liquids and gases and have become the biggest challenge that chemists need to face. Hence, there has been a considerable effort to shift to synthetic methods which would minimise environmental pollution. This is where the concept of green chemistry steps in
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The U.S. Environmental Protection Agency (USEPA) defines green chemistry as the design of chemical products and processes that reduce the generation of hazardous substances. The use and production of these chemicals and processes may involve reduced waste products, non-toxic components and improved efficiency. Green chemistry is a highly effective approach to pollution prevention because it applies innovative scientific solutions to real-world environmental situations. Green chemistry is also known as sustainable chemistry.
KSEEB Class 11 Chemistry Green Chemistry notes
A key difference between environmental chemistry and green chemistry: Environmental chemistry deals with the study of chemical pollutants in the environment whereas green chemistry is concerned with the design of chemicals and processes that minimise toxicity to the environment. This is the key difference between environmental chemistry and green chemistry
1. Applications of Green Chemistry
The term green chemistry was coined by P. T. Anastas who elucidated the principles of green chemistry in his book ‘Green Chemistry:
- Prevention: Prevention of waste is better than treatment or cleanup of waste materials.
- Atom economy: Synthetic methods should be designed such as to maximise the incorporation of all materials into the product.
- Less hazardous chemical synthesis: Synthetic methods should be designed to minimise toxicity to humans and the environment.
- Designing safer chemicals: Chemical products must be designed in a manner that their toxicity is reduced, without affecting their desired functions.
- Safer solvents & Auxiliaries: Use of auxiliary substances (e.g. solvents or separating agents) should be minimised whenever practicable and innocuous when used.
- Design for energy efficiency: Energy requirements for chemical processes should be minimised and alternative routes for conducting synthesis at ambient temperature and pressure should be probed
- Use of renewable feedstocks: Green chemistry encourages the use of renewable resources (raw materials or feedstocks) whenever possible.
- Reduce derivatives: Derivatisation (such as the use of protecting/ de-protecting groups, modification of physical/ chemical processes etc.) leads to the use of additional reagents and the possibility of generating wastes. Such practices should be avoided unless imperative
- Catalysis: Catalytic reagents are superior to stoichiometric reagents.
- Design for degradation: Chemical products should be designed so that they decompose into benign products that do not accumulate in the environment.
- Real-time analysis for pollution prevention: Analytical methodologies should be devised and optimised for real-time, in-process monitoring of chemical processes before the formation of toxic substances.
- Inherently safer chemistry for accident prevention: Substances and the form of substances must be cautiously chosen to avoid the risk of accidents due to accidental release, explosions, fires etc.
2. Contribution of green chemistry
A few classic chemical processes where green chemistry has proved beneficial are outlined below.
Class 11 KSEEB Chemistry Chapter Green Chemistry notes PDF
1. Synthesis of Ibuprofen:
Ibuprofen is the active ingredient of several analgesic and anti-inflammatory drugs. The initial synthesis of ibuprofen consisted of a six-step process with a very poor atom economy. However, recent advances has made possible the synthesis of ibuprofen with an atom economy of more than 90%. This synthesis produces less waste and is a three-step process.
2. Use of dense-phase carbon dioxide:
Dense-phase carbon dioxide is used in both homogeneous and heterogeneous catalysis. Its use allows us to replace organic solvents with chemically inert and environmentally non-toxic carbon dioxide. It is used in the food industry as a reusable solvent to ensure minimal nutrient loss and better preservation of the food products. Dense-phase carbon dioxide may also be used to enhance the quality of cement and to reduce the industrial waste of coal plants.
3. Use of liquid carbon dioxide in dry cleaning:
Carbon dioxide is a new environment-friendly alternative for dry’ cleaning. Liquid carbon dioxide effectively removes stains. At the same time, it is less harmful than perchloroethylene, the solvent which is used by 80% dry cleaners.
4. Use of carbon dioxide as a refrigerant:
Chlorofluorocarbons (CFCs) have been extensively used as refrigerants. However, CFCs are now known to be the prince reason for the ‘ozone hole’ in the stratosphere. Carbon dioxide is now used as a refrigerant and has zero ODP (ozone depletion potential) and minimal CWP (global warming potential).
5. Catalytic hydrogenation of diethyl amine:
A greener approach to the catalytic hydrogenation of diethyl amine furnishes a herbicide with the least environmental toxicity.
KSEEB Class 11 Green Chemistry important questions
6. Antifouling agent Sea-Nine:
Sea-Nine (The Dow Chemical Company) is a rapidly biodegradable settlement inhibitor. It is a highly effective antifoulant against bacterial slime, algae, hydrozoids, etc., and is free from heavy metals. Sea-Nine is a good alternative to organotin compounds which cause aquatic toxicity
7. Paper industry and laundry:
Chlorine has long been used for producing good quality paper from wood (by removing all lignin). However, the use of chlorine leads to the formation of chlorinated hydrocarbons which are known to be potential. H2O2 is now being used as an alternative in the presence of some activators. The use of H2O2 produces lesser environmental concerns.lt is also used in laundry leads lesser use of water.
Green Chemistry notes for Class 11 Chemistry KSEEB
8. Pyrocool foam:
Pyrocool is used in portable fire extinguishers. It uses a non-toxic foam that cools and extinguishes fire without causing risk to human life. It is also free from volatile organic compounds (VOCs), CFCs and carcinogenic chemicals.
9. Synthesis of antibiotics:
Antibiotic drugs like ampicillin and amoxicillin can be synthesised by biochemical methods using environment-friendly enzymes.
Class 11 KSEEB Chemistry Green Chemistry short and long answers
10. Sonochemistry:
Sonochemistry deals with the study of chemical reactions induced by sound waves.
11. Single-step synthesis of ethanal:
A single-step synthesis of ethanal from ethyl alcohol has been studied. This method employs water-soluble ionic catalysts and is environmentally friendly.
12. Fuel cell:
A new variety of fuel cells have been fabricated which can be used as batteries in cell phones. Such fuel cells are based on the combustibility of ethanol.