Green chemistry aims to reduce the environmental impact of chemical processes and products. It focuses on 12 principles including prevention of waste, safer solvents and auxiliaries, atom economy, and designing for energy efficiency and safer chemicals. Examples include using ozone instead of chlorine to disinfect water and oxidizing ethylene to produce acetaldehyde through a catalytic process with lower temperature and hazards compared to traditional methods. Green chemistry provides fundamental approaches to preventing pollution through safer, more sustainable design of chemical products and processes.

1. Green Chemistry

2. Outline
• Definition
• Introduction
• History
• Principles
• Examples
• Conclusion

3. Definition:
“The design of chemical products and processes that are more
environmentally friendly and reduce negative impacts to
human health and the environment”
Introduction:
• It is pollution prevention on the molecular scale and is an
extremely important area of Chemistry due to the importance
of Chemistry in our life
• It supports the invention of more environmentally friendly
chemical processes which reduce or even eliminate the
generation of hazardous substances

4. History
• The concept of green chemistry was formally established at
the “Environmental Protection Agency ” in response to the
Pollution Prevention Act of 1990
• concept was originated by Trevor Kletzin his 1978 paper
where he proposed that chemists should seek processes for
environment
• Paul T. Anastas for the first time in 1991
coined the term Green Chemistry
• Paul T. Anastas is called father of green
chemistry
Paul T. Anastas

5. Principles of Green Chemistry
There are 12 principles of Green Chemistry
• Prevention
• Atom Economy
• Less Hazardous Chemical Synthesis
• Designing Safer Chemicals
• Safer Solvents and Auxiliaries
• Design for Energy Efficiency
• Use of Renewable Feedstock
• Reduce Derivatives
• Catalysis
• Design for Degradation
• Real-time Analysis for Pollution Prevention.
• Inherently Safer Chemistry for Accident Prevention

6. Prevention of Waste:
“It is better to prevent waste than to treat or clean up
waste after it is formed”
• We should carry out a synthesis in such a way that the
waste products is minimum or absent. The waste
discharged in the environment causes pollution
Chemical Process

7. Atom Economy:
“Synthetic methods should be designed to maximize the
incorporation of all materials used in the process into the
final product.”
• reactions are 100% economical reactions if all the reactants
are incorporated into products

8. Less Hazardous Chemical Synthesis:
“ Wherever practicable, synthetic methods should be
designed to use and generate substances that
possess little or no toxicity to people or the
environment. ”
Designing Safer Chemicals:
“ Chemical products should be designed to effect their
desired function while minimising their toxicity. ”

9. 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

11. 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.”
• Association the UK chemical industry's energy efficiency
has improved by 35% in the past 20 years and GHG
emissions have been reduced by 70% over the same
period

12. Use of Renewable Raw Material:
“A raw material or feedstock should be renewable
rather than depleting wherever technically and
economically practicable.”
For example :
• Substances like CO2(generated from natural sources)
and methane gas (marsh gas) are considered as
renewable starting materials
• Solar energy
• Biomass energy

13. 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. ”
More derivatives involve
• Additional Reagents
• Generate more waste products
• More Time
• Higher Cost of Products
Hence, it requires to reduce derivatives

14. Catalysis:
“ Catalysis is the increase in the rate of a chemical reaction
due to the participation of an additional substance called
a catalyst .In most cases, reactions occur faster with a
catalyst because they require less activation energy ”
Examples:
SO2(g) + 1/2 O2(g) SO3(g)
CH3CH2OH(g) +HCl(g) CH3CH2Cl + H2O
V2O5
H2SO4

15. 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 ”
Real-time Analysis:
“Analytical methodologies need to be further
developed to allow for real-time, in-process
monitoring and control prior to the formation of
hazardous substances.”

16. Safer Chemicals For Accident Prevention:
“Analytical 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.”
Example : An incident due to lack of such
measures December 3, 1984 –poison gas
leaked from a Union Carbide factory, killing
hundreds instantly and injuring many more
(many of who died later of exposure)

17. Examples
Disinfection of water
• Disinfection of water by chlorination. Chlorine
oxidizes the pathogens thereby killing them, but at
the same time forms harmful chlorinated
compounds
• A remedy is to use an other oxidant such as O3

18. Synthesis Of Acetaldehyde
• Commercially
Acetaldehyde was obtained by catalytic oxidation of ethyl alcohol or
by hydration of acetylene
CH3CH2OH CH3CHO
• 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 (Pd/Cu and in aqueous medium)
CH2=CH2+O2 CH3CHO
oxidation
oxidation

19. Conclusion
Green Chemistry is about reducing:
• Waste
• Materials
• Hazards
• Risks
• Energy
• Cost
Remember:
Green chemistry is NOT a solution to all environmental
problems BUT the most fundamental approach to
preventing pollution