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1. Green Chemistry

2. Paul Anastas: Father of Green Chemistry 2

3. Green Chemistry is about reducing
•Waste
• Materials
• Hazards
• Risks
• Energy
• Cost
3

4. Why do we need Green Chemistry
Objective
• 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.
Results
• A famous example is the
pesticide DDT.
4

5. What it looks for . . . . .
• 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.
5

6. Goals of Green Chemistry
1. To reduce adverse environmental impact, try appropriate and
innovative choice of material & their chemical transformation.
2. To develop processes based on renewable rather than non-renewable
raw materials.
3. To develop processes that are less prone to obnoxious
chemical release, fires & explosion.
4. To minimize by-products in chemical transformation by
redesign of reactions & reaction sequences.
5. To develop products that are less toxic.
6

7. Goals of Green Chemistry
6. To develop products that degrade more rapidly in the
environment than the current products.
7. To reduce the requirements for hazardous persistent solvents
& extractants in chemical processes.
8. To improve energy efficiency by developing low temperature
& low pressure processes using new catalysts.
9. To develop efficient & reliable methods to monitor the
processes for better & improved controls.
7

8. Principles of
Green Chemistry

9. The 12 Principles of Green Chemistry
1. Prevention of Waste or by-products
http://www.igd.com/wasteprevention
9

10. The 12 Principles of Green Chemistry
1. Prevention of Waste or by-products
“It is better to prevent waste than to treat or clean up
waste after it is formed”
10

11. The 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).
퐴푡표푚 퐸푐표푛표푚푦 =
푀표푙. 푤푒푖푔ℎ푡 표푓 퐷푒푠푖푟푒푑 푝푟표푑푢푐푡
푀표푙. 푤푒푖푔ℎ푡 표푓 푎푙푙 푟푒푎푐푡푎푛푡푠
× 100
11

12. The 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.
12

13. The 12 Principles of Green Chemistry
3. Minimization of hazardous products
13

14. The 12 Principles of Green Chemistry
4. Designing Safer Chemicals
Chemical products should be designed to effect
their desired function while minimising their toxicity.
14

15. The 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”
15

16. The 12 Principles of Green Chemistry 16
5. Safer Solvents & Auxiliaries

17. The 12 Principles of Green Chemistry
6. Design for Energy Efficiency
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.
17

18. The 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
Continue the path toward energy efficiency with
catalysis and product design at the forefront.
18

19. The 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.”
19

20. The 12 Principles of Green Chemistry 20
7. Use of Renewable Feedstock

21. The 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 minimised or
avoided if possible, because such steps require additional
reagents and can generate waste.
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22. The 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.
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23. The 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.
23

24. The 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.
24

25. The 12 Principles of Green Chemistry 25

26. The 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.”
26

27. The 12 Principles of Green Chemistry
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.”
27

28. Efficiency Parameters

29. 1. Reaction Yield
푅푒푎푐푡푖표푛 푌푖푒푙푑 =
퐴푐푡푢푎푙 푌푖푒푙푑
푇ℎ푒표푟푒푡푖푐푎푙 푌푖푒푙푑
× 100
The reaction should have high percentage of yield.
29

30. 2. Atom Economy
Atom economy describes the conversion efficiency of a
chemical process in terms of all atoms involved (desired
products produced).
퐴푡표푚 퐸푐표푛표푚푦 =
푀표푙. 푤푒푖푔ℎ푡 표푓 퐷푒푠푖푟푒푑 푝푟표푑푢푐푡
푀표푙. 푤푒푖푔ℎ푡 표푓 푎푙푙 푟푒푎푐푡푎푛푡푠
× 100
For the reaction, the atom economy should be maximum.
30

31. 2. Atom Economy
e.g.
1. Rearrangement Reactions:
These reactions involves rearrangement of atoms
that forms molecule. Hence, the atom economy of these
reactions are 100%.
2. 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%
31

32. 2. Atom Economy
e.g. Consider the following reaction to find out atom
economy.
32
O
H3C CH2 C OC2H5
+ H3C NH2
Ethyl propionate
Mol wt 102.13
Methyl amine
Mol wt 31.05
O
H3C CH2 C NHCH 3
+ H5C2 OH
Ethyl Alcohol
Mol wt 46.06
N-Methyl propionate
Mol wt 87.106

33. 3. Conversion Factor
Conversion =
Amount of reactant reacted
Amount of reactant taken
× 100
33

34. 4. Reaction Selectivity
Reaction Selectivity =
Amount of desired
product formed
Amount of product expected on
the basis of reactant consumed
× 100
34

35. 5. Environmental Load Factor
It is represented by E and it should be minimum.
E =
푇표푡al mass of effluent formed
푀푎푠s of desired products
× 100
35

36. The major uses of GREEN CHEMISTRY
• Energy
• Global Change
• Resource Depletion
• Food Supply
• Toxics in the Environment