Green chemistry ppt jon

Green Chemistry

1. Name: jon jyoti sahariah m.Pharm (pharmaceutical chemistry) 2 nd semester PRESENTATION ON THE TOPIC GREEN CHEMISTRY DEPARTMENT OF PHARMACEUTICAL SCIENCES DIBRUGARH UNIVERSITY

2. INTRODUCTION Green chemistry is also known as environmentally benign chemistry or sustainable chemistry Paul Anastas and John Warner, who defined green chemistry as the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Chemical developments also bring new environmental problems and harmful unexpected side effects, which result in the need for ‘greener’ chemical products.

3. INTRODUCTION 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 .

4. INTRODUCTION Anastas and Warner formulated the twelve principles of green chemistry in 1998. These serve as guidelines for chemists seeking to lower the ecological footprint of the chemicals they produce and the processes by which such chemicals are made. The invention, design and application of chemical products and processes to reduce or to eliminate the use and generation of hazardous substances .

5. GREEN CHEMISTRY IS ABOUT – Waste Minimisation at Source – Use of Catalysts in place of Reagents – Using Non-Toxic Reagents – Use of Renewable Resources – Improved Atom Efficiency – Use of Solvent Free or Recyclable Environmentally Benign Solvent systems

6. 12 PRINCIPLES OF GREEN CHEMISTRY Prevention of Waste or by-products It is better to prevent waste than to treat or clean up waste after it is formed

7. 12 PRINCIPLES OF GREEN CHEMISTRY 2. Atom Economy Atom economy (atom efficiency) describes the conversion efficiency of a chemical process in terms of all atoms involved (desired products produced). 𝑀𝑜𝑙 . 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝐴𝑡𝑜𝑚 𝐸𝑐𝑜𝑛𝑜𝑚𝑦 = × 100 𝑀𝑜𝑙 . 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑙𝑙 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠

8. 12 PRINCIPLES OF GREEN CHEMISTRY 3. Minimization of hazardous products Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to people or the environment.

9. 12 PRINCIPLES OF GREEN CHEMISTRY 4. Designing Safer Chemicals Chemical products should be designed to effect their desired function while minimising their toxicity.

10. 12 PRINCIPLES OF GREEN CHEMISTRY 5. Safer Solvents & Auxiliaries “The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible, and innocuous when used”

11. 12 PRINCIPLES OF GREEN CHEMISTRY 6. Design for Energy Efficiency Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure .

12. 12 PRINCIPLES OF GREEN CHEMISTRY 6 . Design for Energy Efficiency Developing the alternatives for energy generation (photovoltaic, hydrogen, fuel cells, bio based fuels, etc.) as well as c ontinue the path toward energy efficiency with catalysis and product design at the forefront .

13. 12 PRINCIPLES OF GREEN CHEMISTRY 7 . Use of Renewable Feedstock “ A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.”

14. 12 PRINCIPLES OF GREEN CHEMISTRY 8 . Reduce Derivatives Unnecessary derivatization (use of blocking groups, protection/de-protection, and temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.

15. 12 PRINCIPLES OF GREEN CHEMISTRY 8. Reduce Derivatives More derivatives involve Additional Reagents Generate more waste products More Time Higher Cost of Products Hence , it requires to reduce derivatives.

16. 12 PRINCIPLES OF GREEN CHEMISTRY 9 . Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. e.g. Toluene can be exclusively converted into p- xylene (avoiding o- xylene & m- xylene ) by shape selective zeolite catalyst.

17. 12 PRINCIPLES OF GREEN CHEMISTRY 10. Designing of degradable products 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.

18. 12 PRINCIPLES OF GREEN CHEMISTRY 11. New Analytical Methods “ Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances .”

19. 12. Safer Chemicals For Accident Prevention “ Analytical Substances and the form of a substance used in a chemical process should be chosen to minimise the potential for chemical accidents, including releases, explosions, and fires.”

20. Efficiency Parameter 1. Reaction Yield 𝐴𝑐𝑡𝑢𝑎𝑙 𝑌𝑖𝑒𝑙𝑑 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛 𝑌𝑖𝑒𝑙𝑑 = × 100 𝑇 ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑌𝑖𝑒𝑙𝑑 The reaction should have high percentage of yield .

21. 2. Atom Economy Atom economy describes the conversion efficiency of a chemical process in terms of all atoms involved (desired products produced ).   𝑀𝑜𝑙 . 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝐴𝑡𝑜𝑚 𝐸𝑐𝑜𝑛𝑜𝑚𝑦 = × 100 𝑀𝑜𝑙 . 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑙𝑙 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 For the reaction, the atom economy should be maximum .

22. Atom Economy e.g. Rearrangement Reactions: These reactions involves rearrangement of atoms that forms molecule. Hence, the atom economy of these reactions are 100%. Addition Reactions: These reactions involves addition of two or more molecules without elimination that forms molecule. Hence, the atom economy of these reactions are 100 %

23. Conversion factor: Amount of reactant reacted Conversion = × 100 Amount of reactant taken

24. Reaction Selectivity Reaction Selectivity = Amount of desired product formed x 100 Amount of product expected on the basis of reactant consumed

25. Environmental Load Factor: It is represented by E and it should be minimum . 𝑇𝑜𝑡 al mass of effluent formed E = x100 𝑀𝑎𝑠 s of desired products

26. Microwave assisted Reaction: An approach to green Chemistry Microwave assisted organic synthesis is defined as the preparation of desired organic compound from available starting material via some procedure involving microwave irradiation. As it is less hazardous it is a potential tool of green chemistry. Microwave Synthesis opens up new opportunities to the synthetic chemist in the form of new reaction that are not possible by conventional heating. It is an enabling technology for accelerating drug discovery and development processes .

27. MICROWAVE IRRADIATION Microwave radiation is non-ionizing form of energy that does not alter the molecular structure of compounds and provides only thermal activation .   This phenomenon is dependent on the ability of a specific material to absorb microwave energy and convert into heat . The principle of microwave heating is that the energy can be applied directly to the sample rather than conductively via the vessel. heating can be started or stopped instantly

28. WHAT MICROWAVES ARE? A Microwave is a form of electromagnetic energy that falls at lower frequency at the end of electromagnetic spectrum(300 to 300000MHz ). It is present between infrared radiation and radio waves . Microwave uses EMR that passes through material and causes oscillation of molecules which produces heat.

29. MECHANISM OF MICROWAVE DI ELECTRIC HEATING: Generation of thermal energy in a non conducting material by the application of an electromagnetic force .   wasted energy appears as heat called di - electric loss . The non-metallic material with poor thermal conductivity can be very effectively heated by dielectric heating . Dielectric loss is proportional to frequency and square of the supply voltage . Microwave dielectric heating mechanisms are of 2 types Dipolar polarization mechanism Conduction mechanism

30. Comparison between Microwave and Conventional Method CONVENTIONAL Decrease in reaction rate  Compounds in the mixture heated equally No specific temperature More solvent   Efficient external heating Heat flow: outside to inside MICROWAVE   Increase in reaction rate Specific material is heated Specific temperature Less solvent Efficient internal heating Heat flow: inside to out side

31. Examples of Microwave assisted Reaction:

32. Ultrasound Mediated Reaction  Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz." Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from 'normal' (audible) sound in its physical properties, except in that humans cannot hear it .

33. Ultrasound Mediated Reaction The ultrasound irradiation (also referred to as sonochemistry ) is an important tool in the field of organic chemistry. This technique has become extremely popular in promoting various chemical reactions since the decade 1990–1999. The application of ultrasound has been useful in accelerating dissolution, enhancing the reaction rates, and renewing the surface of a solid reactant or catalyst in a variety of reaction systems. In recent years, the effect of ultrasonic energies in organic synthesis (homogeneous and heterogeneous reactions) has widely increased .

34. Ultrasound Mediated Reaction The use of ultrasound in chemical reactions in solution provides specific activation based on a physical phenomenon. acoustic cavitation . Cavitation is a process in which mechanical activation destroys the attractive forces of molecules in the liquid phase. Applying ultrasound, compression of the liquid is followed by rarefaction (expansion), in which a sudden pressure drop forms small, oscillating bubbles of gaseous substances. These bubbles expand with each cycle of the applied ultrasonic energy until they reach an unstable size; they can then collide and/or violently collapse.

35. Ultrasound Mediated Reaction Two of the most important advantages in the use of sonochemistry in organic synthesis. I ncrease of reaction rates Increase of product yields S o this methodology is more convenient when compared with the traditional method, and it can be easily controlled. For Heterocycles Heterocycles are one of the most popular and important organic compounds because they are involved in many fields of science.

36. Ultrasonic Reactions Esterification : This is generally carried out in presence of a catalyst like sulphuric acid, p- toluenesulphonic acid, tosylchloride , polyphosphoric acid, dicyclohexylcarbodiimide etc. The reaction takes longer time and yields are low.

37. Ultrasonic Reactions Saponification : can be carried out under milder conditions using sonification . Thus , methyl 2,4-dimethylbenzoate on saponification (20 KHz) gives the corresponding acid in 94% yield (Scheme 2), compared to 15% yield by the usual process of heating with aqueous alkali (90 min).