Exploring Green Chemistry: Principles and Environmental Impacts

 
Green Chemistry
 
Chapter 5
 
DEFINITION OF GREEN OR
SUSTAINABLE CHEMISTRY
 
An approach to design, manufacture
and use of chemical products to
deliberately reduce or eliminate the
chemical hazards and protect the
environment.
 
Basic Principles of Green Chemistry
 
12 principles advocated by 
Dr. Paul Anastas
and 
Dr. John Warner
.
1.
Prevention
2.
Atomic Economy
3.
Less Hazardous Chemical Synthesis
4.
Designing Safer Chemicals
5.
Safer Solvents and Auxiliaries
6.
Design for energy efficiency
 
7.
Use of Renewable Feedstocks
8.
Reduce Derivatives
9.
Catalysis
10.
 Design for Degradation
11.
 Real –Time analysis for Pollution prevention
12.
 Essentially Safer Chemistry for Accident
Prevention
 
1. Prevention
 
It is better to prevent waste than to treat
or clean up waste after created it.
So, waste prevention is better than waste
cleanup.
 
Environmental Disasters
 
Love Canal
In Niagara Falls, NY a chemical and plastics company had used an old
canal bed as a chemical dump from 1930s to 1950s. The land was then
used for a new school and housing track. The chemicals leaked through
a clay cap that sealed the dump. It was contaminated with at least 82
chemicals (benzene, chlorinated hydrocarbons, dioxin). Health effects
of the people living there included: high birth defect incidence and
seizure-inducing nervous disease among the children.
 
Cuyahoga River – Cleveland, Ohio
There were many things being dumped in the river such as:
gasoline, oil, paint, and metals. The river was called "
a rainbow
of many different colors
".
 
Some river! Chocolate-brown, oily, bubbling with subsurface gases, it oozes
rather 
 
than flows. "Anyone who falls into the Cuyahoga does not
drown," Cleveland's citizens joke grimly. "He decays."
   
Time Magazine, August 1969
 
2. Atomic Economy
 
      Synthetic methods should be designed to maximize
the incorporation of all materials used in the process
into the final product.
 
Balanced chemical reaction of the epoxidation of styrene
 
 
Atom Economy
 
Atom Economy
% AE = (FW of atoms utilized/FW of all reactants) X 100
 
Balanced Equations
Focuses on the reagents
 
Stoichiometry?
How efficient is the reaction in practice?
Solvents?
Energy?
 
Atom Economy
 
Balanced chemical reaction of the epoxidation of styrene
 
 
Assume 100% yield.
100% of the desired epoxide product is recovered.
100% formation of the co-product: m- chlorobenzoic acid
A.E. of this reaction is 23%.
77% of the products are waste.
 
3. Less Hazardous Chemical Synthesis
 
Synthetic routes should be designed in such a
way that, it generates and uses substances that
possess no or little toxicity to human health
and the environment.
 
Preparation of  acetanilide
 
Conventional method:
 
 
 
 
Green Procedure:
 
 
Non-green components : CH
2
Cl
2
 , Pyridine
Not atom – economic : 1 mole of acetic acid unused.
 
Nitration of phenol
Electrophilic Aromatic Substitution reaction
 
Conventional procedure:
 
 
 
 
Green Procedure:
 
Non-green component
 
Bromination of Acetanilide
 
Conventional procedure:
 
 
 
 
Green Method
 
Non-green component : Liquid molecular bromine
 
4. Designing Safer Chemicals
 
New chemical should be design with great
effectiveness and new approaches to minimize
the toxicity and harmless to the environment.
 
Designing Safer Chemicals
Case Study: Antifoulants (Marine Pesticides
)
 
http://academic.scranton.edu/faculty/CANNM1/environmentalmodule.html
 
 
http://academic.scranton.edu/faculty/CANNM1/environmentalmodule.html
 
Antifoulants are generally dispersed in the
paint as it is applied to the hull. Organotin
compounds have traditionally been used,
particularly tributyltin oxide (TBTO).
TBTO and other organotin antifoulants have
long half-lives in the environment (half-life
of TBTO in seawater is > 6 months). They
also bioconcentrate in marine.
Organotin compounds are chronically toxic
to marine life and can enter food chain. They
are bioaccumulative.
 
5. Safer Solvents and Auxiliaries
 
The auxiliary substances (Inorganic and organic
solvents) should be replaced by safer and eco-
friendly green solvents like IL, supercritical CO
2
fluid, and Supercritical water.
Promote solvent free systems i.e adsorbents like
clays, zeolites, silica, and alumina.
 
Safer solvents: Supercritical fluids
 
    A SCF is defined as a substance above its critical temperature (T
C
) and
critical pressure (P
C
). The critical point represents the highest
temperature and pressure at which the substance can exist as a vapor
and liquid in equilibrium.
 
 
Ionic Liquids (Ils)
 
Liquid at room temperature and below.
Non-volatile
Negligible vapour pressure
Can be recycled
High thermal stability to 200 
o
C or higher
First Room temperature ionic liquid (RTIL) :
Ethylammonium Nitrate [EtNH
3
 ]
+
[NO
3
]
-
 was synthesized
by Paul Walden (1914)  using neutralization method.
 
Supercritical CO
2
 fluid
 
Have low viscosity
No surface tension
Low toxicity
Non-flammability
Easily evaporated leaving no residue
Can dissolve wide range of chemicals
Used in fragrance compounds
 
Supercritical water
 
Water become supercritical at 374
0
C and 218
atm.
Use as a green solvent for many synthetic
reactions.
 
6. Design for Energy Efficiency
 
Energy requirements should be minimized.
Process should be designed to occur at ambient
conditions.
Microwave irradiation, Sonication reaction or
biological processes.
 
- 
Microwave irradiation: Beckmann rearrangement of
oximes without acid catalyst.
 
 -Sonochemistry (Ultrasound Energy): Ullmann’s
coupling.
 
7. Use of Renewable Feedstocks
 
 
A raw material or feedstock should be
renewable rather than depleting
whenever technically and economically
practical.
 
Petroleum Products [Hydrocarbons]
 
8. Reduce Derivatives
 
 
Unnecessary derivatization (blocking
group, protection/deprotection, temporary
modification of physical/chemical
processes) should be avoided whenever
possible.
 
9. Catalysis
 
 
Catalytic reagents (as selective as
possible) are superior to stoichiometric
reagents.
 
10. Design for Degradation
 
 
Chemical products should be designed so that at
the end of their function they do not persist in the
environment and instead break down into
innocuous degradation products.
 
Examples
 
Chlorofluorocarbons (CFCs)
Do not break down, persist in atmosphere and
contribute to destruction of ozone layer
DDT
Bioaccumulate and cause thinning of egg shells
 
11. Real-time Analysis for Pollution
Prevention
 
 
Analytical methodologies need to be
further developed to allow for real-time
in-process monitoring and control prior
to the formation of hazardous
substances.
 
Real time analysis for a chemist
is the process of “checking the
progress of chemical reactions
as it happens.”
 
Knowing when your product is
“done” can save a lot of waste,
time and energy!
 
 
Analyzing a Reaction
 
What do you need to know, how do
you get this information and how
long does it take to get it?
 
12. Inherently Safer Chemistry for
Accident Prevention
 
 
Substance and the form of a substance
used in a chemical process should be
chosen so as to minimize the potential
for chemical accidents, including
releases, explosions, and fires.
 
Phosgene!
Cyanide!
 
 
In arguably the worst industrial accident in history, 40 tons of methyl
isocyanate (MIC) were accidentally released when a holding tank
overheated at a Union Carbide pesticide plant, located in the heart of
the city of Bhopal.  15,000 people died and hundreds of thousands
more were injured.
 
Chemists try to avoid things that explode, light on fire,
are air-sensitive, etc.
 
In the “real world” when these things happen, lives are lost.
 
Tragedy in Bhopal, India - 1984
What happened?
Methyl isocyanate – used to make pesticides was being
stored in large quantities on-site at the plant
Methyl isocyanate is highly reactive, exothermic
molecule
Most safety systems either failed or were inoperative
Water was released into the tank holding the methyl
isocyanate
The reaction occurred and the methyl isocyanate rapidly
boiled producing large quantities of toxic gas.
 
Conclusion
 
G
r
e
e
n
 
c
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e
m
i
s
t
r
y
 
 
N
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a
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e
n
v
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r
o
n
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t
a
l
 
p
r
o
b
l
e
m
s
 
B
u
t
t
h
e
 
m
o
s
t
 
f
u
n
d
a
m
e
n
t
a
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a
p
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o
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t
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p
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o
n
.
 
Thank you
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Understanding the principles of green chemistry, such as waste prevention and atomic economy, is crucial for designing chemical products that reduce environmental hazards. Environmental disasters like Love Canal and Cuyahoga River highlight the importance of sustainable practices in the chemical industry.


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  1. Green Chemistry Chapter 5

  2. DEFINITION OF GREEN OR SUSTAINABLE CHEMISTRY An approach to design, manufacture and use of chemical products to deliberately reduce or eliminate the chemical hazards and protect the environment.

  3. Basic Principles of Green Chemistry 12 principles advocated by Dr. Paul Anastas and Dr. John Warner. 1. Prevention 2. Atomic Economy 3. Less Hazardous Chemical Synthesis 4. Designing Safer Chemicals 5. Safer Solvents and Auxiliaries 6. Design for energy efficiency

  4. 7. Use of Renewable Feedstocks 8. Reduce Derivatives 9. Catalysis 10. Design for Degradation 11. Real Time analysis for Pollution prevention 12. Essentially Safer Chemistry for Accident Prevention

  5. 1. Prevention It is better to prevent waste than to treat or clean up waste after created it. So, waste prevention is better than waste cleanup.

  6. Environmental Disasters Love Canal In Niagara Falls, NY a chemical and plastics company had used an old canal bed as a chemical dump from 1930s to 1950s. The land was then used for a new school and housing track. The chemicals leaked through a clay cap that sealed the dump. It was contaminated with at least 82 chemicals (benzene, chlorinated hydrocarbons, dioxin). Health effects of the people living there included: high birth defect incidence and seizure-inducing nervous disease among the children.

  7. Cuyahoga River Cleveland, Ohio There were many things being dumped in the river such as: gasoline, oil, paint, and metals. The river was called "a rainbow of many different colors". Some river! Chocolate-brown, oily, bubbling with subsurface gases, it oozes rather than flows. "Anyone who falls into the Cuyahoga does not drown," Cleveland's citizens joke grimly. "He decays." Time Magazine, August 1969 acc01

  8. 2. Atomic Economy Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.

  9. Atom Economy Atom Economy % AE = (FW of atoms utilized/FW of all reactants) X 100 Balanced Equations Focuses on the reagents Stoichiometry? How efficient is the reaction in practice? Solvents? Energy?

  10. Atom Economy Balanced chemical reaction of the epoxidation of styrene O O O O OH OH + + Cl Cl Assume 100% yield. 100% of the desired epoxide product is recovered. 100% formation of the co-product: m- chlorobenzoic acid A.E. of this reaction is 23%. 77% of the products are waste.

  11. 3. Less Hazardous Chemical Synthesis Synthetic routes should be designed in such a way that, it generates and uses substances that possess no or little toxicity to human health and the environment.

  12. Preparation of acetanilide Conventional method: O O O Pyridine H2N N H O CH2Cl2 aniline acetic anhydride acetanilide Non-green components : CH2Cl2 , Pyridine Not atom economic : 1 mole of acetic acid unused. Green Procedure: O Zn dust H2N CH3COOH N H boil aniline acetanilide

  13. Nitration of phenol Electrophilic Aromatic Substitution reaction Conventional procedure: OH O- O NaNO3 N+ HO N+ OH H2SO4 -O O phenol p-nitrophenol o-nitrophenol Non-green component Green Procedure: OH COOH OH COOH Ca(NO3)2 acetic acid NO2 salicylic acid 4-nitrosalicylic acid

  14. Bromination of Acetanilide Conventional procedure: NHCOCH3 NHCOCH3 Br2 Glacial acetic acid Br Non-green component : Liquid molecular bromine Green Method Br NHCOCH3 O KBr Cerric ammonium nitrate N H H2O EtOH p-bromoacetanilide

  15. 4. Designing Safer Chemicals New chemical should be design with great effectiveness and new approaches to minimize the toxicity and harmless to the environment.

  16. 5. Safer Solvents and Auxiliaries The auxiliary substances (Inorganic and organic solvents) should be replaced by safer and eco- friendly green solvents like IL, supercritical CO2 fluid, and Supercritical water. Promote solvent free systems i.e adsorbents like clays, zeolites, silica, and alumina.

  17. Safer solvents: Supercritical fluids A SCF is defined as a substance above its critical temperature (TC) and critical pressure (PC). The critical point represents the highest temperature and pressure at which the substance can exist as a vapor and liquid in equilibrium.

  18. Ionic Liquids (Ils) Liquid at room temperature and below. Non-volatile Negligible vapour pressure Can be recycled High thermal stability to 200 oC or higher First Room temperature ionic liquid (RTIL) : Ethylammonium Nitrate [EtNH3 ]+[NO3]- was synthesized by Paul Walden (1914) using neutralization method.

  19. Supercritical CO2 fluid Have low viscosity No surface tension Low toxicity Non-flammability Easily evaporated leaving no residue Can dissolve wide range of chemicals Used in fragrance compounds

  20. Supercritical water Water become supercritical at 3740C and 218 atm. Use as a green solvent for many synthetic reactions.

  21. 6. Design for Energy Efficiency Energy requirements should be minimized. Process should be designed to occur at ambient conditions. Microwave irradiation, Sonication reaction or biological processes. - Microwave irradiation: Beckmann rearrangement of oximes without acid catalyst. -Sonochemistry (Ultrasound Energy): Ullmann s coupling.

  22. 7. Use of Renewable Feedstocks A raw material or feedstock should be renewable rather than depleting whenever technically and economically practical.

  23. Biomaterials [Carbohydrates, Proteins, Lipids] Highly Functionalized Molecules Petroleum Products [Hydrocarbons] Singly Functionalized Compounds [Olefins, Alkylchlorides] Highly Functionalized Molecules

  24. 8. Reduce Derivatives Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.

  25. 9. Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.

  26. 10. Design for Degradation Chemical products should be designed so that at the end of their function they do not persist in the environment and instead break down into innocuous degradation products.

  27. Examples Chlorofluorocarbons (CFCs) Do not break down, persist in atmosphere and contribute to destruction of ozone layer DDT Bioaccumulate and cause thinning of egg shells

  28. 11. Real-time Analysis for Pollution Prevention Analytical methodologies need to be further developed to allow for real-time in-process monitoring and control prior to the formation of hazardous substances.

  29. Real time analysis for a chemist is the process of checking the progress of chemical reactions as it happens. Knowing when your product is done can save a lot of waste, time and energy!

  30. Analyzing a Reaction What do you need to know, how do you get this information and how long does it take to get it?

  31. 12. Inherently Safer Chemistry for Accident Prevention Substance and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires.

  32. Cyanide! Phosgene!

  33. Tragedy in Bhopal, India - 1984 What happened? Methyl isocyanate used to make pesticides was being stored in large quantities on-site at the plant Methyl isocyanate is highly reactive, exothermic molecule Most safety systems either failed or were inoperative Water was released into the tank holding the methyl isocyanate The reaction occurred and the methyl isocyanate rapidly boiled producing large quantities of toxic gas.

  34. Conclusion Green chemistryNot a solution to all environmental problems But the most fundamental approach to preventing pollution.

  35. Thank you

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