I hope it will be helpful to readers..

1. Presented By: Ayesha Ishfaq
Roll # 357

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4. Waste
Materials
Hazards
Risks
Energy
Cost
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5. 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.
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6. To reduce adverse environmental impact, try appropriate and
innovative choice of material & their chemical transformation.
To develop processes based on renewable rather than non-renewable
raw materials.
To develop processes that are less prone to obnoxious chemical
release, fires & explosion.
To minimize by-products in chemical transformation by redesign of
reactions & reaction sequences.
To develop products that are less toxic.
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7. To develop products that degrade more rapidly in the environment
than the current products.
To reduce the requirements for hazardous persistent solvents &
extractants in chemical processes.
To improve energy efficiency by developing low temperature & low
pressure processes using new catalysts.
To develop efficient & reliable methods to monitor the processes
for better & improved controls.
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10. “It is better to prevent waste than to treat or clean up waste after it is
formed”
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11. It is the measure of waste.
It is represented by E and it should be minimum.
E =
푇표푡al mass of effluent formed
푀푎푠s of desired products
× 100
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12. “Synthetic methods should be designed to maximize
incorporation of all materials used in the process into the final
product”
Atom economy (atom efficiency) describes the conversion efficiency
of a chemical process in terms of all atoms involved (desired
products produced).
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13. Traditionally, the efficiency of a reaction has been measured by calculating the
percent yield.
 Let us assume that the following substitution reaction gives 100% yield. While
this is admirable, we can shed more light on the efficiency of a reaction by
calculating the “percent atom economy” as follows:
퐴푡표푚 퐸푐표푛표푚푦 =
푀표푙. 푤푒푖푔ℎ푡 표푓 퐷푒푠푖푟푒푑 푝푟표푑푢푐푡
푀표푙. 푤푒푖푔ℎ푡 표푓 푎푙푙 푟푒푎푐푡푎푛푡푠
× 100
= (137/275) X 100 = 50%
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14. Simply put, even if our percent yield is 100%, only half the mass of
the reactants atoms are incorporated in the desired product while the
other half is wasted in unwanted by-products.
Imagine telling your mom you baked a cake and threw away half the
ingredients!
Thus chemists must not only strive to achieve maximum percent
yield, but also design syntheses that maximize the incorporation of
the atoms of the reactants into the desired product.
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15. “Wherever practicable, synthetic methods should be designed to
use and generate substances that possess little or no toxicity to
people or the environment”
“wherever practicable.” Saying those two words implies that it may
not be practical or possible to avoid using substances that are
toxic, and that’s why most chemists use to try to avoid applying
this principle to their work.
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16. “Chemical products should be designed to effect their desired
function while minimising their toxicity”
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17. Achieving this goal requires an understanding of not only chemistry
but also of the principles of toxicology and environmental science.
Highly reactive chemicals are often used by chemists to manufacture
products because they are quite valuable at affecting molecular
transformations.
However, they are also more likely to react with unintended biological
targets, human and ecological, resulting in unwanted adverse effects.
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18. “The use of auxiliary substances (e.g. solvents, separation
agents, etc.) should be made unnecessary wherever
possible, and innocuous when used”
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19. Choose solvents that make sense chemically, reduce the energy
requirements, have the least toxicity, have the fewest life cycle
environmental impacts and don't have major safety impacts.
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20. “Energy requirements of chemical processes should be recognised for
their environmental and economic impacts and should be minimised. If
possible, synthetic methods should be conducted at ambient
temperature and pressure”
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21. Developing the alternatives for energy generation (photovoltaic,
hydrogen, fuel cells, bio based fuels, etc.) as well as
Continue the path toward energy efficiency with catalysis and
product design at the forefront.
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22. “A raw material or feedstock should be renewable rather than
depleting whenever technically and economically practicable”
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23. In the past 10 years, significant advances have been made in the
development of fuels, chemicals and materials from renewable feed
stocks from “thin air” with minimal impact on human health and the
environment.
These for example, have included biodiesel from plant oils and
algae, bioethanol and butanol from sugars and lignocellulose,
plastics, foams and thermosets from lignin and plant oils, and even
electronic materials from chicken feathers.
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24. “Unnecessary derivatization (use of blocking groups,
protection/de-protection, and temporary modification of
physical/chemical processes) should be minimised or avoided if
possible, because such steps require additional reagents and can
generate waste”
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25. One of the best ways of doing this is the use of enzymes.
Enzymes are so specific that they can often react with one site of the
molecule and leave the rest of the molecule alone and hence
protecting groups are often not required.
A great example of the use of enzymes to avoid protecting groups
and clean up processes is the industrial synthesis of semi-synthetic
antibiotics such as ampicillin and amoxicillin
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26. “Catalytic reagents (as selective as possible) are superior to
stoichiometric reagents”
A catalyst is defined as “a substance that changes the velocity of a
reaction without itself being changed in the process”. It lowers the
activation energy of the reaction but in so doing it is not consumed.
This means that, in principle at least, it can be used in small amounts
and be recycled indefinitely, that is it doesn’t generate any waste.
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27. The reduction of a ketone to the corresponding secondary alcohol using
sodium borohydride or molecular hydrogen as the reductant.
Reduction with the former has an atom economy of 81% while reduction
with the latter are 100% atom economic, that is everything ends up in the
product and, in principle, there is no waste.
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28. “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”
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29. Green chemistry principles 3, 4, 5, and 12 guide designers to reduce
the hazards of chemicals.
Principle 10, however, guides the design of products that degrade
after their commercial function in order to reduce risk or the
probability of harm occurring.
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30. “Analytical methodologies need to be further developed to allow for
real-time, in-process monitoring and control prior to the formation of
hazardous substances.”
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31. Most chemists are familiar with laboratory analysis from their
undergraduate training.
But analysis can also be performed in-line, on-line, or at-line in a
chemical plant, a sub-discipline known as process analytical
chemistry.
Such analysis can detect changes in process temperature or pH
prior to a reaction going out of control, poisoning of catalysts can be
determined, and other deleterious events can be detected before a
major incident occurs.
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32. “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”
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33. Green Chemistry Principle # 12 is known as the “Safety Principle”.
It may be the most overlooked of the twelve principles, yet it is the
logical outcome of many of the other principles. In fact it is practically
impossible to achieve the goals of Principle 12 without the
implementation of at least one of the others.
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34. The major uses of GREEN CHEMISTRY
Energy
Global Change
Resource Depletion
Food Supply
Toxics in the Environment
Computer Chips
Medicine
Biodegradable Plastics
Paint

35. Green chemistry offers a different approach to conventional
chemistry and engineering through the thoughtful application of
principles that aid the design of sustainable chemical products and
processes by focusing individuals on the development of innovative
solutions, opportunities, and challenges.
Applying these principles collectively will result in products and
processes that protect and benefit the economy, people, and the
planet and help us make significant strides toward a more
sustainable future.
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36. http://www.slideshare.net/hecrod/green-chemistry3985228?
related=1
http://www.slideshare.net/Santachem/green-chemistry-15990119
http://www.acs.org/content/acs/en/greenchemistry/what-is-green-chemistry/
principles.html
http://www.acs.org/content/acs/en/greenchemistry/what-is-green-chemistry/
principles/12-principles-of-green-chemistry.html
http://www.epa.gov/sciencematters/june2011/principles.htm
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