Title GREEN CHEMISTRY - 22-1-25.pdf ✅

i GREEN CHEMISTRY Table of Contents UNIT-I..................................................................249 1. Introduction ..............................................249 1.1. Need for Green Chemistry....................249 1.2. Goals of Green Chemistry. ...................250 1.3. Limitations of Green Chemistry. ..........250 1.4. Chemical accidents...............................251 1.5. Terminologies.......................................253 1.6. International green chemistry organizations 260 1.7. Twelve principles of Green Chemistry with examples...........................................................260 UNIT-II.................................................................261 2. Choice of starting materials......................261 2.1. Choice reagents.....................................263 2.2. Choice catalysts....................................263 2.3. and solvents in detail,Error! Bookmark not defined. 2.4. Green chemistry in day today life.........264 2.5. Designing green synthesis....................265 green reagents:..................................................265 2.6. dimethyl carbonate. ..............................265 2.7. Green solvents: .....................................265 Water ............................................................... 266 Ionic liquids..................................................... 266 2.8. General methods of preparation........... 272 2.9. Supercritical carbon dioxide ................ 275 2.10. Advantages & Drawbacks ............... 277 2.11. a few examples of organic reactions in scCO2. 278 2.12. Green synthesis-adipic acid and catechol. 278 UNIT-III .............................................................. 279 3. Environmental pollution .......................... 279 3.1. Green Catalysis.................................... 281 3.2. Acid catalysts....................................... 281 3.3. Oxidation catalysts............................... 284 3.4. Basic catalysts...................................... 285 Polymer supported catalysts............................ 285 3.5. Poly styrene aluminum chloride .......... 285 3.6. polymeric super acid catalysts............. 285 3.7. Poly supported photosensitizers........... 286 UNIT-IV .............................................................. 286 4. Phase transfer catalysis in green synthesis286 4.1. oxidation using hydrogen peroxide...... 288 4.2. crown ethers......................................... 288 4.3. Esterification........................................ 289 4.4. Saponification...................................... 289 4.5. Anhydride formation,........................... 290 4.6. Elimination reaction............................. 290 4.7. Displacement reaction.......................... 290 4.8. Applications in organic synthesis. ....... 290
ii UNIT-V ................................................................291 5. Micro wave induced green synthesis........291 5.1. Introduction ..........................................291 5.2. Instrumentation.....................................292 5.3. Principle and applications.....................293 5.4. Sonochemistry......................................299 5.5. Instrumentation.....................................300 5.6. Applications..........................................301
249 UNIT-I 1. Introduction The term green chemistry is defined as: “The invention, design and application of chemical products and processes to reduce or to eliminate the use and generation of hazardous substances”. (Or) “Green chemistry is the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products." (Or) "Green chemistry consists of chemicals and chemical processes designed to reduce or eliminate negative environmental impacts. The use and production of these chemicals may involve reduced waste products, non-toxic components, and improved efficiency."  Prevents pollution at the molecular level  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.  Results in source reduction because it prevents the generation of pollution  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. 1.1. Need for Green Chemistry. Chemistry is undeniably a very prominent part of our daily lives.  Chemical developments also bring new environmental problems and harmful unexpected side effects, which result in the need for ‘greener’ chemical products.  A famous example is the pesticide DDT.  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.  This program works very closely with the twelve principles of Green Chemistry. Green chemistry is about:  Waste Minimization 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 The Benefits of Green Chemistry:  • Economical  • Energy efficient
250  • Lowers cost of production and regulation  • Less wastes • Fewer accidents  • Safer products  • Healthier workplaces and communities  • Protects human health and the environment  • Competitive Advantage 1.2. Goals of Green Chemistry. Green Chemistry aims to eliminate or at least reduce the pollution by preventing it from happening as far as possible. In fact the goal of green chemistry or benign chemistry is to design synthetic methodologies that reduce or eliminate the use or generation of toxicproducts. In order to be eco- friendly, organic synthesis must meet all or some of the following requirements. They are:  avoid waste  avoid use and production of toxic and hazardous chemicals  avoid auxiliary substances  reduce energy requirements  use catalysts like bio-catalysts  produce compounds which are biodegradable In broad sense, green chemistry includes any chemical process or technology that improves the environment and thus enhances the quality of life. 1.3. Limitations of Green Chemistry. Environmental pollution can be eliminated or considerably reduced by following the principles of green chemistry. The most important principles (as we will see subsequently) include using renewable resources as starting materials in a chemical synthesis, using safer chemicals, economizing on atoms, using minimum energy for a process and discharging only the safe substances (or by-products) into the environment. However, a number of things that limit and there are constrains the goals of green chemistry. Some of these include: • It is not always possible to procure starting materials for a reaction from renewable resources. • Use of benign or safer solvents is not always possible. If feasible, a particular reaction could be conducted without using any solvent, in solid state. • It is not always possible to economise on atoms. This means that all the atoms of the starting materials cannot be incorporated into the final products. It is well known that only rearrangement reactions and addition reactions are 100% atom economical. All other reactions are not atom- economical. • It is not always possible to discharge only the safer by-products into the environment. It is very important to formulate guidelines and pass strict rules for the practising chemists. But the most important is to bring about changes at the grass root level, which can be achieved by bringing about