ISSN No: 2395-3306

Int. J. Chem. Pharm. Rev. Res. Vol (3), Issue (2), 2016, Page. 1-6

Review Article

International Journal of Chemical and Pharmaceutical Review and Research www.ijcprr.com/browse-journal

Green Chemistry: The Atom Economy Pradip K. Jenaa*, Susanta K. Sahub and A. Samantaraya a

Department of Chemistry, College of Basic Science and Humanities, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha, India. b University Department of Pharmaceutical Science, Utkal University, Bhubaneswar, Odisha, India. A R T I C L E

I N F O

Article history: Received 14 May 2016 Accepted 20 June 2016 Available online 28 June 2016 Keywords: Green chemistry, Atom economy, Sustainable development.

A B S T R A C T

Green Chemistry can be defined as the practice of chemical science and manufacturing in a manner that is sustainable, safe and non-polluting, which consumes minimum amount of materials and energy that producing little or no waste material. It usually deals with increasing profits and promoting innovation while protecting human health and the environment. Basically green chemistry garnishes a vast body of chemical knowledge and applies it to the production, use and ultimate dispose of chemicals in a way that minimizes consumption of materials, exposure of living organisms (including humans) to toxic substances and damage to the environment. The success of it depends on the training and education of a new generation of Chemists. Industrialists, Scientists, Researchers and Students at all levels to introduce the philosophy and practice of green chemistry. © IJCPRR All rights reserved.

The limitation of a command and control system for environmental protection has become more obvious even as the system has become more successful1. The first conference highlighting green chemistry was held in Washington in 1997. Since that time other similar scientific conferences have soon held on a regular basis. The first books and journals on the subject of green chemistry were introduced in the 1990s, including the Journal of Clean Processes and Products (Springer-Verlag) and Green Chemistry, sponsored by the Royal Society of Chemistry. Other journals, such as Environmental Science and Technology and the Journal of Chemical Education, have devoted sections to green chemistry. The actual information also may be found on the Internet 2.

1. Introduction The term green chemistry was first used in 1991 by P.T. Anastas in a special programme initiated by the Environmental Protection Agency (EPA) to implement sustainable development in Chemistry and Chemical Technology by Industry, Academia and Government. In 1995 the Annual US Presidential Green Chemistry Challenge was announced. In 1996 the working party on Green Chemistry was created, acting within the framework of International Union of Pure and Applied Chemistry(IUPAC). One year later, the Green Chemistry Institute (GCI) was formed with chapters in 20 countries to facilitate contact between governmental agencies and industrial corporations with universities and research institutes to design and implement new technologies.

Green Chemistry can be defined as the practice of chemical science and manufacturing in a manner that is sustainable, safe and non-polluting which consumes minimum amount of materials and energy that producing little or no waste material. In accomplishing its objectives, green chemistry and green chemical engineering may modify or totally redesign chemical products and processes with the objective of minimizing wastes and the use or generation of particularly dangerous materials.

_______________________________ * Corresponding author. E-mail address: [email protected] Present address: Department of Chemistry, College of Basic Science and Humanities, OUAT, Bhubaneswar, Odisha, India

1

ISSN No: 2395-3306

Int. J. Chem. Pharm. Rev. Res. Vol (3), Issue (2), 2016, Page. 1-6

Green Chemistry usually deals with increasing profits and promoting innovation while protecting human health and the environment. Basically, It garnishes a vast body of chemical knowledge and applies it to the production, use and ultimate dispose of chemicals in a way that minimizes consumption of materials, exposure of living organisms, (including humans) to toxic substances and damage to the environment. In brief “Green Chemistry” follows the principle:- “Prevention is better than Cure”. Further in short, Green Chemistry is defined as: - Designing the chemical processes and products that reduce or eliminate the use and formation of hazardous substances. The main purposes of Green Chemistry are mentioned below:-

Review Article

2. The twelve principles of Green Chemistry: Anastas and Warner have formulated the twelve principles of Green Chemistry as the guidelines or blueprint for practicing green chemistry to save the environment. These principles are given below. 1. Prevention - To minimize the waste product formation, it is better to prevent the formation of waste than to treat or clean up the waste after its formation. It aims to develop the zero waste technology (ZWT). In terms of ZWT, in a chemical synthesis, waste product should be zero or minimum. It also aims to use the waste product of one system as the raw material for other systems. For example, bottom ash of thermal power station can be used as a raw material for cement and brick industry; effluent coming out from cleaning of machinery parts may be used as coolant water in thermal power station; municipal waste as a source of energy; etc. Such practices will reduce the waste product.

i. Eco friendly chemical technology: Green Chemistry aims to protect the environment and that is why it is also termed as “Environmental Benign Chemistry. ii. Replacement of organic solvent and to minimize the waste production: Green Chemistry aims to devise greener reaction conditions for the synthesis of chemicals so that waste product (toxic waste) formation can be minimized. It needs the replacement of organic solvent by water or complete elimination of the use of solvent. It also needs to minimize the formation of by-products (specially the hazardous substances).

2. Atom economy: This concept developed by Trost, focuses attention on how many of the atoms of the reactants are incorporated into the final desired product and how many are wasted. During the synthesis of a chemical product, the methodology should be designed in a way to maximize the incorporation of starring materials into the desired final product. Thus it demands to minimize the formation of by-product.

iii. Use of renewable feed stocks: Green chemistry aims to develop the greener synthesis of the required chemical products by using the renewable resources (e.g. biomass rather than petrochemical feed stocks). It reduces the consumption of nonrenewable resources (e.g. Crude Oil).

3. To avoid the use and formation of toxic materials: The synthetic methodologies should avoid the use and generation of toxic and environmentally hazardous substances. It aims to develop the methodologies that will minimize the use, formation of toxic and hazardous substances. In other words, the synthetic methodologies should use and generate the ecofriendly substances that will show little or no toxicity to human health and environment.

iv. To minimize the energy consumption : Green chemistry aims to develop the greener conditions for the synthesis of chemical products so that energy consumption can be minimized, for many existing chemical technologies, drastic reaction conditions (e.g. high temperature, high pressure, etc.) which are energy requiring are applied. Greener synthesis aims to develop the mild or modest reaction conditions. Ideality, the reactions should be carried out at ambient temperature and pressure.

4. Use of nontoxic chemical products: Chemical products to be used in different activities should have the efficacy to function but with reduced toxicity. In many chemical industries, not only the waste product but the starting materials are also quite hazardous to the workers and environment. For example, adipic acid, HO2C(CH2)4CO2H is widely used in polymer industries (cf. manufacture of nylon, polyurethane, lubricants, etc.). Benzene is the starting materials for the synthesis of adipic acid but benzene is carcinogenic and benzene being a VOC pollutes air. In green technology developed by Drath and Frost, adipic acid is enzymetically synthesized from glucose.

v. Use of more eco friendly chemical products: Green chemistry aims to design the new chemical products to replace the existing hazardous chemical products provided the new chemicals are having the same desirable properties of the existing ones (e.g. development of new pesticide which is only toxic to the target species and at the same time it biodegrades easily, to harmless products). vi. Four R's (4R's): These four R's are: Reduction (at source), Recycling, Reuse and Recovery of wastes.

2

ISSN No: 2395-3306

Int. J. Chem. Pharm. Rev. Res. Vol (3), Issue (2), 2016, Page. 1-6

5. Minimum use of auxiliary substances: If possible (both technically and economically), in a chemical synthesis, the use of auxiliary substances like solvents, separating agents, etc. should be avoided. If, these are to be used they should be eco-friendly. This principle aims to use green solvents (e.g. water, supercritical CO2) in place of volatile halogenated organic solvents e.g. CH2Cl2, CHCl3, CCl4 for chemical synthesis and other purposes. Solvent free synthesis should be preferred. For example, Claisen rearrangement can be carried out in solid phase.

Review Article

temporary modification of physical and chemical processes etc., should be avoided as far as possible during the synthesis of a chemical product. Thus there should be a minimum number of steps to synthesize a target product. Especially in organic synthesis, we need very often protection of some functional groups. Finally, we again need their deprotection. It is illustrated in the following example of synthesis of m-hydroxybenzoic acid from mhydroxybenzaldehyde. Obviously, in such cases, atom economy is also less. The green chemistry principle aims to develop the methodology where unnecessary steps should be avoided, if practicable. Biocatalytic reactions very often need no protection of selective groups.

6. Minimum energy consumption : In the synthesis of a chemical product, the energy consumption should be minimized to make the process more and more economic. Ideally, the synthetic methods should be carried out at ambient temperature and pressure.To save energy, synthetic methodologies should need more and more moderate conditions and the ambient temperature and pressure are the best choices. It needs suitable catalysts that will accelerate the reaction rate even at lower temperature. The biocatalysts (i.e. enzymes) can work at the ambient conditions. Energy save can be done in many other ways : refluxing conditions require less energy; waste heat may be used for heating the reactants and other things; improving the technology of heating system; preference for photochemical reactions (specially by using the solar radiation) instead of thermochemical reactions; extraction of energy from the waste product; use of microwave heating etc.These practices advocate the concept of green energy as demanded by the 6th principle.

9. Use of catalytic reagents: Selective catalytic reagents are superior to stoichiometric reagents in a chemical synthesis. This will save the energy and reduce the burden of by-product.This principle of green chemistry states that catalytic reagents are superior to stoichiometric reagents. The use of catalysts is preferred because of the following advantages. (i) 100% atom economy because the true catalysts are fully recovered without any change in their chemical and physical properties; (ii) the catalyzed reactions are faster i.e. energy save is possible; (iii) reaction yields are better; (iv) selective reaction products; (v) maximum utilization of the starting material and minimum production of the waste material. 10. Life-time of a chemical product: At the end of function, the chemical products (e,g. pesticides) should degrade easily to harmless products, i.e. after their function, they should not persist in the environment.DDT is the classic example in this area. It is an effective pesticide but its stability in the natural environment causes several environmental hazards. It states that the waste product should degrade automatically to clean the environment. Thus the biodegradable polymers and pesticides are always preferred. Sometimes, the polymers are to be made degradable photochemically. Here it should be mentioned that the degraded products should not be toxic.

7. Use of renewable sources: If it is technically and economically possible, then the renewable resources (e.g. biomass) rather than the nonrenewable resources (e.g. crude oil) should be used as the raw material or feedstock. It encourages the use of starting material (i.e. raw material or feedstock) which should be renewable, if technically and economically practicable. In fact, continuous use (i.e. over exploitation) of the nonrenewable feedstock (e.g. petroleum product, fossil fuel) will deplete the resource and future generation will be deprived. Moreover, use of these nonrenewable resources puts a burden on the environment. On the other hand, use of sustainable or renewable resources e.g. agricultural or biological product ensures the sharing of resources by future generation. Moreover, this practice generally does not put much burden on the environment. The products and wastes are generally biodegradable.

11.

Monitoring the generation of hazardous substances: Analytical methodologies should be further developed to allow for real-time in-process monitoring and control prior to the generation of hazardous substances in the synthesis of chemical products. Analytical methodologies should be developed or modified, so that continuous monitoring of the manufacturing and processing units is possible. This is very much important for the chemical industries and nuclear reactors. This

8. Minimization of steps: If possible, the steps like blocking group, protection/deprotection of group,

3

ISSN No: 2395-3306

Int. J. Chem. Pharm. Rev. Res. Vol (3), Issue (2), 2016, Page. 1-6

efficient monitoring is quite essential to avoid the accident.

Review Article

For example, if the chemical process works with the gaseous substances, then the possibility of accidents including explosion is relatively higher compared to the systems working with the nonvolatile liquid and solid substances. In fact, the risk is minimum if the process works with solid substances at every step.

12. Use of chemically safer substances: The substances to be used in a chemical reaction should be selected in such a way that they can minimize the occurrence of chemical accidents, explosions, fires and emissions. In other words, the substances to be used should not be hazardous. The substances used in chemical industries should be in such forms so that the possibility of accidents can be minimized.

More examples for implementing the 12 principles in laboratory and industry are presented in Table 1.

Table 1. Examples of implementation of green chemistry principles into practise. Sl. No.

Principle

Example

1

Prevention

2

Atom economy

3

To avoid the use and formation of toxic materials

4

Use of nontoxic chemical products

New, less hazardous pesticide synthesis (e.g.spinosad) 5

5

Minimum use of auxiliary substances

Synthesis in ionic liquids and Super critical fluid extraction6

6

Energy efficiency

7

Use of renewable sources

8

Minimization of steps

9

Catalysis

10

Life-time of a chemical product

11

Monitoring the generation of hazardous substances

12

Use of chemically safer substances

Use of solvent-less sample preparation technique3 Hydrogenation of carboxylic acid to aldehyde using solid catalysts Synthesis of adipic acid from cyclohexene using hydrogen peroxide4

Polyolefin – Polymer alternative to PWC7 Production of surfactant8 On – fibre derivatization vs derivatization in solution in sample preparation9 Use of Au(III) catalyzed synthesis of b-enaminones from 1,3- dicarbonyl compounds and amines 10 Synthesis of biodegradable polymers 11 Use of in-line analyser for waste water monitering

Di – Me Carbonate (DMC) is an environment friendly substitute for Di-Me Sulfate and Mehalides in Methylation reaction 12

4

ISSN No: 2395-3306

Int. J. Chem. Pharm. Rev. Res. Vol (3), Issue (2), 2016, Page. 1-6

Review Article

4. The concept of atom economy in chemical synthesis

3. Implementation of Green Chemistry Principles into Practice:

Atom economy is an important development beyond the traditionally taught concept of percent yield. Barry Trost, from Stanford University, published the concept tof atom economy in Science in 1991 15. In 1998 he received the Presidential Green Chemistry Challenge Award 16 for his work. At the award ceremony, Paul Anderson(1997 ACS President) commented, “By introducing the concept of ‘atom economy,’ Dr.Trost has begun to change the way in which chemists measure the efficiency of the reactions they design.” Atom economy answers the basic question, “How much of what you put into your pot ends up in your product?” 17. To meet the challenge of atom economy, Trost has developed a number of palladium and ruthenium catalysts. These catalysts enable chemical synthesis to proceed by simple addition reactions 18.

In some industrial chemical processes, not only waste products but also the reagents used for the production, may cause a threat to the environment. The risk of exposure to hazardous chemical compounds is limited in daily work by protective equipment such as goggles, breathing apparatus, face-guard masks, etc. According to the principles of green chemistry, it can be eliminated in a simpler way by applying safe raw materials for production process. For example, large amounts of adipic acid [HOOC(CH2)4COOH] are used each year for the production of nylon, polyurethanes, lubricants and plasticizers. Benzene - a compound with convinced carcinogenic properties - is a standard substrate for the production of this acid. Chemists from State University of Michigan developed green synthesis of adipic acid using a less toxic substrate. Furthermore, the natural source of this raw material - glucose - is almost inexhaustible. The glucose can be converted into adipic acid by an enzyme discovered in genetically modificated bacteria 13. Such a manner of production of this acid guards the workers and the environment from exposure to hazardous chemical compounds.

To synthesize a particular chemical product, all the atoms of the reactants used may not be always incorporated in the desired product. The atoms which are not incorporated in the product are involved to generate the by-product and waste product which may be environmentally hazardous. To have a quantitative idea regarding the amount of waste product and byproduct generated in a particular reaction, we can consider the idea of % atom utilization defined as follows:

Green chemistry tries, when possible to utilize benign renewable feedstocks as raw materials. From the point view of green chemistry, combustion of fuels obtained from renewable feedstocks is more preferable than combustion of fossil fuels from depleting finite sources. For example, many vehicles around the world are fueled with diesel oil and the production of biodiesel oil is a promising possibility. As the name indicates, biodiesel oil is produced from cultivated plants oil, e.g. from soya beans. It is synthesized from fats embedded in plant oils by removing the glycerin molecule, a valuable raw material for soap production.

% Atom utilization 

Formula weight of the desired product  100 Formula weight of (the desired product  the waste and by  product )

But, very often it is difficult to identify the waste and byproducts. To avoid this, the concept of % atom economy has been introduced.The concept of atom economy also gives the measure of the unwanted product produced in a particular reaction. It is defined as follows : % Atom economy 

Formula weight of the desired product  100 Sum of formula weight of the all reac tan ts used in the reaction

The concept of % atom economy is illustrated in the following examples. Green synthesis of acetophenone : Classical oxidation of 1-phenylethanol consumes the stoichiometric amounts of CrO3 and H2SO4. Consequently its % atom economy is less. On the other hand, catalytic oxidation by O2 enjoys the higher atom economy.Thus the catalytic reactions (e.g. synthesis of methyl methacrylate, acetophenone, etc.) always possess the higher atom economy compared to the reactions consuming the reactants in stoichiometric amounts. Vasicine, an abundantly available quinazoline alkaloid from the leaves of Adhatoda vasica, enables an efficient metal- and base-free reduction of nitroarenes to the corresponding anilines in water. The chemoselective method tolerates a wide range of reducible functional groups, such as ketones, nitriles, esters, halogens, and heterocyclic rings. Dinitroarenes are reduced selectively to the corresponding nitroanilines19. A general, efficient,

Biodiesel oil also can be obtained from wasted plant oils, e.g. oils used in restaurants. In the technological process, a potential waste product is transformed into valuable fuel. (Combusted biodiesel oil smells like fried potatoes.) The advantages of using biodiesel oil are obvious. Its fuel from renewable resources and contrary to normal diesel oil, the combustion of biodiesel does not generate sulphur compounds and generally does not in crease the amount of carbon dioxide in the atmosphere. CO2 formed in the combustion of fuel was removed earlier by plants 14.

5

ISSN No: 2395-3306

Int. J. Chem. Pharm. Rev. Res. Vol (3), Issue (2), 2016, Page. 1-6

Review Article

and metal-free method for aerobic oxidation of primary benzylamines to the corresponding oximes in good yields is catalyzed by N,N′,N″-trihydroxyisocyanuric acid in the presence of acetaldoxime and water as solvent. This practical method uses air as economic and green oxidant, water as green solvent, and tolerates a wide range of substrates20.

7. Romano U., Garbassi F. The environmental issue. A challenge for new generation polyolefins. Pure Appl.Chem., 72, 1383-1388, (2000).

5. Conclusion

9. Stashenko E. E., Puertas A. M., Salgar W., Delgadow., Martinez J. R. Solid-phase microextractionwith on fibre derivatization applied to the analysis of volatile carbonyl compounds. J. Chromatography A., 886, 175-182, (2000).

8. Niclos N., Benvegnu T., Plusquellec D. Surfactantsfrom renewable resources. Actualite Chimique, 70, 11-12, (2002).

Green chemistry in not a new stem of science. It is a new rational approach that through application and extension of the principles of green chemistry can contribute to sustainable development. Great efforts are still undertaken to design an ideal process that starts from non polluting initial materials leads to no secondary products and requires no solvents to carryout chemical conversion or to isolate and purify the product. Furthermore, the success of it depends on the training and education of a new generation of Chemists, Industrialists, Scientists, Researchers and Students at all levels to introduce the philosophy and practice of green chemistry.

10. Acardi A., Bianchi G., DI Giuseppe S.,MARINELLIF. Gold catalysis in the reaction of 1,3-dicarbonyls withnucleophiles. Green Chemistry. 5 (1), 64, (2003). 11. Scott G. Green polymers. Polym. Degrad. Stab. 68 (1),1-7, (2000). 12. Tundo P., Selva M., Memoli S. Dimethylcarbonate asa green reagent. ACS Symp. Ser., 767 (Green Chemical Synthesses and Processes), 87, (2000).

References 1. Anastas P. T., Warner J. C. Green Chemistry: Theory and Practise. Oxford University Press, Oxford 1998

13. Karen M. Draths, John W. Frost, Environmentally compatible synthesis of adipic acid from D-glucose,J. Am. Chem. Soc., 116 (1), 399–400, (1994).

2. W. Wardencki, J. Curyo, J. Namieœnik: Green Chemistry — Current and Future Issues. Polish Journal of Environmental Studies, 14, ( 4), 389-395, (2005).

14. Ivana B. Banković-Ilić, Olivera S. Stamenković, Vlada B. Veljković, Biodiesel production from non-edible plant oils. Renewable and Sustainable Energy Reviews, 16(6), 3621–3647, (2012). 15. Trost, B. M. Science, 254, 1471-1477, (1991).

3. Namieoenik J., Wardencki W. Solventless sample preparation techniques in environmental analysis. J. High Resol. Chromatogr. 23, 297, (2000).

16. http://www.epa.gov/greenchemistry/presgcc.html 17. Trost, B. M. In The Presidential Green Chemistry Challenge Awards Program: Summary of the 1998 Award Entries and Recipients; EPA744-R-98-001, U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics:Washington, DC, p 2, (1998).

4. Sato K., Aoki M., Noyori R. A “Green” Route toAdipic Acid: Direct Oxidation of Cyclohexenes with 30 percent hydrogen peroxide. Science. 281, 1646, (1998). 5. http:// www.epa.gov/greenchemistry

18. Trost, B. M. Acc. Chem. Res. 35, 695-705, (2002).

6. Bardley D., Dyson P., Welton T. Room temperature ionic liquids. Chem. Rev. 9 (5), 18, (2000).

19. S. Sharma, M. Kumar, V. Kumar, N. Kumar, J. Org. Chem., 79, 9433-9439, (2014). 20. J. Yu, M. Lu, Synlett, 25, 1873-1878, (2014).

6