GREEN CHEMISTRY
By
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Dr. Kandikere Ramaiah Prabhu
Principal Research Scientist
Department of Organic Chemistry
Indian Institute of Science
Bangalore – 560 012
October 23, 2010, Bangalore
History…..
Green Chemistry is born around 199o
What is green chemistry or Sustainable Technology
Traditionally - Chemical Yield was paramount
Green Chemistry Focuses on Process efficiency in terms of
eliminating wastes at source and avoid
using or generating toxic substances
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12 Principals of green chemistry

Prevention

Atom Economy

Less Hazardous Chemical Syntheses

Designing Safer Chemicals

Safer Solvents and Auxiliaries

Design for Energy Efficiency
It is better to prevent waste than to treat or clean up waste after it has been created.
Synthetic methods should be designed to maximize the incorporation of all materials used
in the process into the final product.
Wherever practicable, synthetic methods should be designed to use and generate
substances that possess little or no toxicity to human health and the environment.
Chemical products should be designed to effect their desired function while minimizing
their toxicity.
The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made
unnecessary wherever possible and innocuous when used.
Energy requirements of chemical processes should be recognized for their environmental
and economic impacts and should be minimized. If possible, synthetic methods should be
conducted at ambient temperature and pressure.
 Use of Renewable Feedstocks
A raw material or feedstock should be renewable rather than depleting whenever technically
and economically practicable.
 Reduce Derivatives
Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary
modification of physical/chemical processes) should be minimized or avoided if possible, because
such steps require additional reagents and can generate waste.
 Catalysis
Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
 Design for Degradation
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.
 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.
 Inherently Safer Chemistry for Accident Prevention
Substances and the form of a substance used in a chemical process should be chosen to
minimize the potential for chemical accidents, including releases, explosions, and fires.
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
E-Factor???
 Mass ratio of waste to desired product
 Higher e-factor – more waste and –ve
environmental impact
 Raw Materials-Product output
product
The key to waste minimization is precision
in organic synthesis,
where every atom counts!!!
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
Atom efficiency
Molecular weight of the product
Sum molecular weight of the
all products formed
Atom efficiency of stoichiometric versus catalytic oxidation of alcohols
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Additional questions!!??
Environmental impact of waste!!
Waste can be an useful output
What is the waste generated in manufacture of Organic compounds???
Fine chemicals and pharmaceuticals use stoichiometric amounts of reagents
Reductions – Metal hydride
Oxidations - CrO3, KMnO4,etc
Sulfonation, Nitration, Friedel-Crafts reaction etc……!!!!
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The technologies used for the production of many substituted
aromatic compounds have not changed in more than a century and
are, therefore, ripe for substitution by catalytic, low-salt
alternatives
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Two routes to hydroquinones
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
Catalysts

Homogeneous catalyst & Heterogeneous catalysts


Organocatalyst
Biocatalysts
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Homogeneous catalyst & Heterogeneous catalysts
Organocatalyst
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DEVELOPMENT CATALYSIS
IN
ORGANIC SYNTHESIS
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If the solution to the waste problem in the fine chemicals
industry is so obvious
Replacement of classical stoichiometric reagents with cleaner,
catalytic alternatives
Why was it not applied in the past?
There are several reasons for this.
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


First, because of the smaller quantities compared
with
bulk chemicals, the need for waste reduction
in fine chemicals was not widely appreciated.
A second, underlying, reason is the more or less
separate evolution of organic chemistry and catalysis.
Fine chemicals and pharmaceuticals have remained
primarily the domain of synthetic organic chemists
who, generally speaking, have clung to the use of
classical “stoichiometric” methodologies and have
been reluctant to apply catalytic
alternatives.
A third reason, which partly explains the
reluctance, is the pressure of time. Fine
chemicals generally have a much shorter lifecycle
than
bulk
chemicals
and,
especially
in
pharmaceuticals, ‘time to market’ is crucial.
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Major points to be addressed
Catalysts
Solvents
Renewable Raw Materials – White biotechnology
Risky Reagents
Process integration and catalytic cascades
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Catalysts
Acid base catalyst
Heterogeneous catalysts
Homogeneous catalyst
Solid catalysts
Bio catalyst
Organo catalysts
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Acid base catalyst
Montmorillonite clays
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Zeolites
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Reductions
Catalytic reductions
Hydrogen gas
Hydrogenation catalysts
Selectivity in hydrogenation
Chiral reductions
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oxidations
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Biocatalysts
Egs:
Yeast-ADH as alcohol dehydrogenase
Horse liver-ADH
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Organocatalysis
Proline-catalyzed aldol reaction
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O
Our Research…!!!!
O
S Mo S
H3C
N
S
S
H3C
Transition Metal oxides
Chemical transformations
Metal-oxo complexes
X
XO
M Oxidized
X
MReduced
Reduction
XO
CH3
CH3
Academia & Industry.
Oxidations & reductions processes.
Oxidation
N
 Oxygen is transformed from Molecular Oxygen
M. Maddani, K. R. Prabhu,
Tetrahedron Lett., 2008, 49, 4526
Oxidation of Alcohols to Carbonyls Catalysed by Molybdenum Xanthate
OH
MoO2(Et2NCS2)2
CHO
No reaction
Toluene/Water
Reflux, 40h
Heterogeneous catalysts
Liquid phases
Recovery, recycling and Stability.
NH2
Amm.persulphate Aq Ammonia
1.5MHCl
+ in 1.5MHCl
+
+ MoO2(X)2
Acetonitrile
RT, 50h
Polyaniline
MoO2(X)2
3
= Polyaniline
Proposed polyaniline-supported MoO2(X)2 structure.
Efficiency of the catalyst
H
OH
MeO
Run
Catalyst 3, O2
O
Toluene, Reflux, 20h
Product (Yield %)
MeO
Recovery of PASMOX
1.
98
>99 %
2.
95
>98 %
3.
92
>96 %
M. Maddani, K. R. Prabhu,
Unpublished Results
II


Disposal or decomposition protocols for
hydrazine and its derivatives by using
user friendly protocols
Convert surplus high energy materials
to safer products
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R.A. BACK, Reviews of Chemical Intermediates, 5 (1984) 293—323
C.Willis, R.A.Back, International Journal of chemical kinetics, 1977, 9, 787
IN
SEARCH OF CATALYST FOR HYDROGENATION
USING HYDRAZINE HYDRATE
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METHOD FOR THE AEROBIC HYDROGENATION OF OLEFINS
Method for the generation of diimide
 using metal Catalyst
H2NNH2, CuSO4, air
H2NNH2, CuSO4, H2O2
H2NNH2, CuSO4, O2
Metals such as mercuric oxide and Hexacyanoferrate(III) are also used
along with hydrazine hydrate
E.J. Corey, W.L. Mock .D.J. Pasto Tetrahedron Lett. 1961, 347-352
S. Huitig, H. R. Miiller, W. Thier, Tetrahedron Lett. 1961, 353.
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From Azodicarboxylates (acid catalyzed hydrolysis)
Thermal decomposition of arenesulfonyl hydrazides
E. E. van Tamelen, R. S. Dewey, J. Am. Chem. Soc. 1961 83 3729 .
E.J. Corey, W.L. Mock .D.J. Pasto Tetrahedron Letters 1961, 347-352
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Flavin-Catalyzed Generation of Diimide
Y. Imada, H. Iida, T. Naota, J. Am. Chem. Soc. 2005, 127, 14544-14545

Reduction of Carbon-Carbon Double Bonds
Using Diimide genearted by using
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C. Smit, M. W. Fraaije, A. J. Minnaard, J. Org. Chem. 2008, 73, 9482–9485
Flavin-Catalyzed Generation of Diimide
Y. Imada, H. Iida, T. Naota, J. Am. Chem. Soc. 2005, 127, 14544-14545
Reduction of Carbon-Carbon Double Bonds
Using diamide generated by an Organocatalyst
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C. Smit, M. W. Fraaije, A. J. Minnaard, J. Org. Chem. 2008, 73, 9482–9485
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MECHANISM FOR
OXIDATIVE CLEAVAGE OF
HYDRATE USING
HYDRAZINE
FLAVIN CATALYST
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Y. Imada, H. Iida, T. Naota, J. Am Chem. Soc. 2005, 127, 14544-14545
ENVIRONMENTALLY BENIGN METHOD FOR
THE AEROBIC HYDROGENATION OF OLEFINS
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REDUCTION
OF ALKENES AND ALKYNES
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DRUGS WITH CHIRAL METHYL GROUP
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SYNTHETIC
SCHEME
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ENANTIOSELECTIVE REDUCTION
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Tehshik P. Yoon, Eric N. Jacobsen*, Science 2003:Vol. 299. no. 5613, pp. 1691 - 1693
Andreas Pfaltz * and William J. Drury III, PNAS April 20, 2004 vol. 101 no. 16 5723-5726
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Conclusion
P
Prevent waste
R
Renewable raw material
O
Omit derivatization steps
D
Degradable Chemical Product
U
Use of safe synthetic methods
C
Catalytic reagents
T
Temperature, Pressure ambient
I
In – process monitoring
V
Very few auxiliary substrates
E
E-factor, atom efficiency
L
Low toxicity of chemical products
Y
Yes, it is safe
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Acknowledgements
Dr. Mahagundappa Maddani
Mr. Manjunath Lamani
Mr. GS Ravikumar
IISc, AMRB, RL Fine Chem
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