Green chemistry, Its Applications and Benefits

Introduction to the concept of Green Chemistry and why is it a viable option to switch into.

1. Green Chemistry
NOTjust a definite solution…
BUTan ultimate necessity…

2. Some light upon the term-Green Chemistry:
Definition-“The design of chemical products and processes that are more
environmentally friendly and reduce negative impacts to human health and the
environment.”
Green chemistrylooks 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 Chemistryprogram supports the invention of more environmentally
friendly chemical processes which reduce or even eliminate the generation of
hazardous substances.
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3. Father of Green Chemistry
The concept of green chemistry was
formally established at the
ENVIRONMENTAL PROTECTION AGENCY
15 years ago in response to the Pollution
Prevention Act of 1990.
Paul T. Anastas for the first time in 1991coined the
term Green Chemistry. Though it is said that the
concept was originated byTrevor Kletzin his 1978
paper where he proposed that chemists should seek
alternative processes to those involving more
dangeroussubstances and conditions.
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4. Principles of Green Chemistry
Paul T. Anastas and John C. Warner developed 12 principles of green
chemistry, which help to explain what the definition means in practice.
a.Prevention
b.Atom Economy
c.Less Hazardous Chemical
Synthesis
d.Designing Safer Chemicals
e.Safer Solvents and Auxiliaries
f.Design for Energy Efficiency
g.Use of Renewable Feedstocks
h.Reduce Derivatives
i.Catalysis
j.Design for Degradation
k.Real-time Analysis for Pollution
Prevention.
l.Inherently Safer Chemistry for
Accident Prevention.
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5. 1.Prevention:
“It is better to prevent waste than to treat or clean up waste
after it is formed.”
It is advantageous to carry out a synthesis in such a way that the
formation of waste products is minimum or absent. The waste if discharged
in the atmosphere, sea and land causes not only pollution but also requires
expenditure for cleaning up.
Chemical Process
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6. Some dreadful examples of ill effects from
untreated waste disposal:
1.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.
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7. continued…
2.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".
•Fires erupted on the river several times before June
22, 1969, when a river fire captured national attention
when Time Magazine reported it.
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.“
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8. 2.Atom Economy:
“Synthetic methods should be designed to maximize the
incorporation of all materials used in the process into the final
product.”
A synthesis is Perfectly Efficient or Atom Economicalif it generates
significant amount of waste which is not visible in percentage yield
calculation.
Percent yield:
%Yield=
actualyield)
theoreticalyield
���
Atom Economy:
%AE=
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(????????????��??????����??????��??????���
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9. RearrangementandAdditionreactions are 100% atom economical
reactions since all the reactants are incorporated into products.
While SubstitutionandEliminationreactions are less atom
economical.
1. H
3C-CH=CH
2+ H
2 H
3C-CH
2-CH
3
propene propane
the reaction takes place in presence of Nickel.Here 64.8%reactants
are incorporated into product. Hence this is an atom economical
reaction.
2. CH
3(CH
2)
4CH
2OH +SOCl
2 SO
2+ CH
3(CH
2)
4CH
2Cl
this reaction is less atom economical as the % atom economy is 36.5%.
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10. 3.Less Hazardous Chemical Synthesis
“Wherever practicable, synthetic methodologies should be designed to use
and generate substances that possess little or no toxicity to human health
and the environment.”
Example of an unsafe drug is THALIDOMIDE
for lessening the effect of nausea and
vomiting during pregnancy. The child born to
women taking the drug suffers from birth
defects like deformed-limbs.
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11. Another example but with a remedial
substitute:
Polycarbonate Synthesis:
1.Phosgene Process
Disadvantages:-
1.phosgene is highly toxic, corrosive
2.requires large amount of CH
2Cl
2
3.polycarbonate contaminated with Cl impuritiesOH OH
Cl Cl
O
+
NaOH
O O *
O
*
n

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12. 2. Solid-State Process
Advantages:
1.diphenylcarbonatesynthesized without phosgene
2.eliminates use of CH
2Cl
2
3.higher-quality polycarbonatesOH OH
+ O O *
O
*
n

O O
O
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13. 4.Designing Safer Chemicals
“Chemical products should be designed to preserve efficacy of function while
reducing toxicity.”
•Synthetic methodologies should be designed to generate substances that
generate substances that possess less harmful or toxic products.
•This principle focuses on choosing reagents that pose the least risk and
generate only safe by-products.
•For example: in the manufacture of Polystyrene, CFC’swhich contribute to
ozone depletion and global warming are replaced by CO
2.
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14. 5.Safer Solvents and Auxiliaries
“The use of auxiliary substances (e.g. solvents, separation agents, etc.) should
be made unnecessary wherever possible and innocuous when used .”
•The solvent selected for a particular reaction shouldn't cause any
environmental pollution or hazard (e.g. benzene, alcohol).
•One major problem with many solvents is their volatility that may damage
environment and human health.
•To avoid this many reactions are carried out in safer green solvents like ionic
liquids, supercritical CO
2fluid etc. which maintain the solvency of the material
and are also non-volatile.
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15. Solvent selection
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16. Solvent replacement table
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17. 6.Design for Energy Efficiency
“Energy requirements should be recognized for their environmental and
economic impacts and should be minimized. Synthetic methods should be
conducted at ambient temperature and pressure .”
In any chemical synthesis the energy requirement should be kept low ,for example:
1) If the starting material is soluble in the particular solvent, the reaction mixture
has to be heated till the reaction is complete.
2) If the final product is impure it has to be purified by distillation or
recrystallization .
All these steps involve the use of high amount of energy which is uneconomical.
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18. 7.Use of Renewable Feedstocks
“A raw material or feedstock should be renewable rather than depleting
wherever technically and economically practicable.”
Renewable feedstock are often made from agricultural products or are the wastes
of other processes; depleting feedstock are made from fossil fuels (petroleum,
natural gas or coal) or are mined.
For example :-
Substances like CO
2(generated from natural sources) and methane gas (marsh
gas) are considered as renewable starting materials.
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19. Polymers from Renewable Resources:
Poly(lactic acid)
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20. Raw Materials from Renewable Resources:
The BioFine Process
Paper mill
sludge
Agricultural
residues,
Waste wood
Municipal solid waste
and waste paperO
HO
O
Levulinic acid
Green Chemistry Challenge Award
1999 Small Business Award
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21. Levulinic acid as a platform chemical
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22. 8.Reduce Derivatives
“Reduce derivatives -Unnecessary derivatization (blocking group,
protection/deprotection, temporary modification) should be avoided
whenever possible.”
Avoid using blocking or protecting groups or any temporary modifications if
possible. Derivatives use additional reagents and generate more waste.
Two synthetic steps are added each time when one is used. Overall yield and atom
economy decrease.
Instead, more selective and better alternative synthetic sequences that eliminate
the need for functional group protection should be adopted.
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23. 9.Catalysis
“Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.”
Use of a catalyst facilitates transformation without the catalyst being consumed in the
reaction and without being incorporated in the final product.
Some advantages of catalyst are:
1)Better yields
H
3C-CH=CH
2 + H
2 H
3C-CH
2-CH
3
Propene Propane
the hydrogenation of olefins is carried out in presence of nickel.
2)The reaction becomes feasible in those cases where no reaction is normally possible.
3)Better utilization of starting material and minimum waste product formation.
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24. 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 break down into innocuous degradation products .”
For example-
•Sulfonated detergents
Alkylbenzene sulfonates –1950’s & 60’s
Foam in sewage plants, rivers and streams
Persistence was due to long alkyl chain
Introduction of alkene group into the chain increased degradation
•Chlorofluorocarbons (CFCs)
Do not break down, persist in atmosphere and contribute to destruction of ozone layer
•DDT
Insecticides like DDT tend to bio-accumulate in many plant and animal species and incorporate
into the food chain resulting in population decline of beneficial insects and animals.
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25. 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!
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26. 12.Inherently Safer Chemistry for
Accident Prevention
“Substances and the form of a substance used in a chemical process should
be chosen to minimize potential for chemical accidents, including releases,
explosions, and fires.”
Design chemicals and their forms (solid, liquid, or gas) to minimize the potential
for chemical accidents including explosions, fires and releases to the environment.
Example of such incident due to lack of such measures:-
December 3, 1984 –poison gas leaked from a Union Carbide factory, killing
thousands instantly and injuring many more (many of who died later of exposure).
Up to 20,000 people have died as a result of exposure (3-8,000 instantly). More
than 120,000 still suffer from ailments caused by exposure.
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27. Synthesis Of Some Industrial
Compounds Involving Basic
Principles Of Green Chemistry
Ibuprofen
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28. Synthesis Of Acetaldehyde
Commercially
•Acetaldehyde was obtained by catalytic oxidation of ethyl alcoholor by
hydration of acetylene.
•CH
3CH
2OH
oxidation
CH
3CHO
•The above reaction occurs at a very high temperature (675K).
Green Synthesis Of Acetaldehyde
•It is most conveniently obtained by oxidation of ethylene in presence of
catalyst solution.
•CH
2=CH
2+O
2
oxidation
CH
3CHO
•The reaction takes place in the presence of Pd/Cu and in aqueous medium.
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29. Free Radical Bromination
•The usual Bromination of toluene with N-bbomosuccinimide(NBS)
gives benzyl bromide. This process requires a solvent (CCl4).
•It has been found that free radical bromination of toluene with
NBS in supercritical carbon dioxide gave 100% yield of benzyl
bromide.
•Toluene
(hv,NBS,CO2,139 bar) Benzyl bromide(100%)
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30. Synthesis Of AdipicAcid
•Adipicacid is required in large
quantities for synthesis of nylonand
lubricants.
•But Adipicacid is obtained from benzene
which causes environmental and health
problems. Also, nitrous oxide is
generated as by-product which causes
greenhouse effect.
•Green synthesis of adipicaciduses
D-glucose(renewable source) as starting
material. Also the synthesis is conducted
in water instead of organic solvents.
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31. Disinfection of water
•Disinfectionofwaterbychlorination.Chlorineoxidizesthepathogensthereby
killingthem,butatthesametimeformsharmfulchlorinatedcompounds.
•Aremedyistouseanotheroxidant,suchasO
3orsupercriticalwateroxidation.
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32. Production of allyl alcohol
CH
2=CHCH
2OH
•Traditionalroute:Alkalinehydrolysisofallylchloride,whichgeneratesthe
productandhydrochloricacidasaby-product
•Greenerroute,toavoidchlorine:Two-step;usingpropylene(CH
2=CHCH
3),
aceticacid(CH
3COOH)andoxygen(O
2)
•Addedbenefit:Theaceticacidproducedinthe2
nd
reactioncanberecovered
andusedagainforthe1
st
reaction,leavingnounwantedby-product.CH
2=CHCH
2Cl + H
2O CH
2=CHCH
2OH + HCl
problem product CH
2=CHCH
3 + CH
3COOH + 1/
2 O
2
CH
2=CHCH
2OCOCH
3 + H
2O CH
2=CHCH
2OCOCH
3 + H
2O CH
2=CHCH
2OH + CH
3COOH
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33. Production of styrene (benzene ring with
CH=CH
2tail)
•Traditionalroute:Two-stepmethodstartingwithbenzene,whichiscarcinogenic)and
ethylenetoformethylbenzene,followedbydehydrogenationtoobtainstyrene
•Greenerroute:Toavoidbenzene,startwithxylene(cheapestsourceofaromaticsand
environmentallysaferthanbenzene).
•Anotheroption,stillunderdevelopment,istostartwithtoluene(benzeneringwith
CH
3tail).+ H
2C=CH
2
catayst
CH
2CH
3
ethylbenzene catayst
CH=CH
2CH
2-CH
3
ethylbenzene
styrene
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34. Synthesis Of Ibuprofen
•Ibuprofen is one of the products used in large quantities for
making pharmaceutical drugs, in particular various kinds analgesics
(pain killers).
•The traditional commercial synthesis of ibuprofen was developed
by the Boots Company of England in1960s. It is a 6 step
process and results in large quantities of by-products. There is
40% atom economy in this synthesis.
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35. conti…Classic Route to Ibuprofen…Ac
2
O
AlCl
3
COCH
3
HCl, AcOH, Al Waste
ClCH
2
CO
2
Et
NaOEt
O
EtO
2
C
HCl
H
2
O / H+
OHC
AcOH
NH
2
OH
OHN
N
H
2
O / H+
HO
2
C
NH
3
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36. conti…Green Synthesis Of Ibuprofen
The BHC Companydeveloped a new greener synthesis of Ibuprofen that consists
only of 3 steps. It results in small amount of unwanted products and has very good
atom economy(77%).O
HF
AcOH
Ac
2
O
H
2
/ Ni
OH
CO, Pd
HO
2
C
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37. Conclusion
As Paul T. Anastas said that his dream is not that Green
Chemistry is practiced by every person but rather whole
Chemistry is Green.
Remember:-
Green chemistry is NOTa solution to all environmental
problems BUTthe most fundamental approach to preventing
pollution.
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38. Acknowledgement
I am really thankful to my teacher Dr. ShuchiDhingrawho
gave me this topic as my project and had faith in my work.
Her sincere help and devotion has led me to fulfillment of this
presentation.
I would also like to thank my family, my parents, my friends
and above all my brother Summit Amola whose utmost help
led me to finalize my presentation.
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