1. A PROJECT BY:- MOINAK SARKAR
NILAY JOSHI
PUSHTY TALATI
PRADYUT TALUKDAR
Class XI-B…
2. Definition-“The design of chemical products and processes that are
more environmentally friendly and reduce negative impacts to human
health and the environment.”
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.
3. The concept of green chemistry was
formally established at the
ENVIRONMENTAL PROTECTION
AGENCY 25 years ago in response to the
Pollution Prevention Act of 1990.
Paul T. Anastas for the first time in 1991
coined the term Green Chemistry. Though
it is said that the concept was originated by
Trevor Kletz in his 1978 paper where he
proposed that chemists should seek
alternative processes to those involving
more dangerous substances and
conditions.
5. Prevent
Waste
Maximize Atom
Economy
Less Hazardous
Chemical
Syntheses
Safer Chemical
and Products
Safer solvent
and reaction
conditions
Increase Energy
Efficiency
Use renewable
Feedstock
Avoid Chemical
Derivatives
Use catalysts
Design chemical and
products to degrade
after use
Analyze in real
time to prevent
pollution
Minimize Potential
for accidents
6. 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.
7. 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.
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
Economical if it generates significant amount of
waste which is not visible in percentage yield
calculation.
Percent yield:
(actual yield/theoretical yield) * 100
Atomic Economy:
(%AE)=(FW of atoms utilized/FW of all reactants) *
100
9. 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.
10. 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’s which contribute to ozone depletion and
global warming are replaced by CO2.
11. 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
CO2fluid etc. which maintain the solvency of the
material and are also non-volatile.
12. 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
13. 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 CO2 ( generated from natural
sources )
And methane gas are considered as renewable
starting materials.
14. 8. Reduce derivatives
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 atom economy decrease .
Instead , more selective and better alternative
synthetic sequences that eliminate the need for
functional group protection should be adopted
15. 9.Catalysis
Use of a catalyst transformation without the
catalyst being consumed in the reaction and
without being incorporated in the final product .
Some advantages of catalyst are :
BETTER YIELDS
CH3-CH=CH2 + H2 CH3-CH2-CH3
( propene ) ( propane)
The hydrogenation of olefins is carried out in the
presence of nickel .
16. 10. Design for degradation
For example:
Sulfonated detergents :
Alkyl benzene sulfonates-1950s& 60s.
Foam in sewage plants, rivers and streams .
Persistence was due to long alkyl chain .
Introduction of alkene group into the chain
increased degradation.
2. Chlorofluorocarbons ( CFCs )
Do not breakdown , persist in atmosphere and
contribute to destruction of ozone layer
17. 3. DDT
Insecticides like DDT tend to bio- accumulate in
many plant and animal species and incorporate into
food chains resulting in population decline of
beneficial insects and animals .
18. 11. REAL-TIME ANALYSIS FOR
POLLUTION PREVENTION
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 !
19. 12. Inherently safer chemistry
for accident prevention
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 an 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 . More than 120,000 still suffer from
ailments caused by exposure .
20. BENEFITS OF GREEN CHEMISTRY
Human health:
Cleaner air: Less release of hazardous chemicals to
air leading to less damage to lungs
Cleaner water: less release of hazardous chemical
wastes to water leading to cleaner drinking and
recreational water
Increased safety for workers in the chemical
industry; less use of toxic materials; less personal
protective equipment required; less potential for
accidents (e.g., fires or explosions)
21. Safer consumer products of all types: new, safer
products will become available for purchase; some
products (e.g., drugs) will be made with less
waste; some products (i.e., pesticides, cleaning
products) will be replacements for less safe
products
Safer food: elimination of persistent toxic
chemicals that can enter the food chain; safer
pesticides that are toxic only to specific pests and
degrade rapidly after use
Less exposure to such toxic chemicals as endocrine
disruptors
22. Environment:
Green chemicals either degrade to innocuous products or
are recovered for further use.
Plants and animals suffer less harm from toxic chemicals
in the environment.
Lower potential for global warming, ozone depletion,
and smog formation.
Less chemical disruption of ecosystems.
Less use of landfills, especially hazardous waste
landfills.
23. Economy and business:
Higher yields for chemical reactions, consuming
smaller amounts of feedstock to obtain the same
amount of product
Fewer synthetic steps, often allowing faster
manufacturing of products, increasing plant
capacity, and saving energy and water
Reduced waste, eliminating costly remediation,
hazardous waste disposal, and end-of-the-pipe
treatments
Increased consumer sale by earning and displaying
a safer product label
24. Reduced use of petroleum products,
slowing their depletion and avoiding their
hazards and price fluctuations
Reduced manufacturing plant size or
footprint through increased throughput
Improved competitiveness of chemical
manufacturers and their customers
25. 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 NOT a solution to all
environmental problems BUT the most
fundamental approach to preventing pollution.
