1) Green chemistry is the design of chemical products and processes that reduce or eliminate the use of hazardous substances. It encourages more economical and environmentally friendly techniques.
2) There are 12 principles of green chemistry developed by Anastas and Warner to guide reducing environmental impacts, including preventing waste generation, designing safer chemicals and solvents, using renewable feedstocks, and catalysis.
3) Various metrics have been developed to quantify the environmental performance of chemical processes, like carbon efficiency, atom economy, and environmental factor, though developing universally applicable metrics remains challenging.
2. What is Green Chemistry ?
Design of chemical products and processes that reduce or eliminate the use
or generation of substances hazardous to humans, animals, plants, and the
environment.
Green chemistry discusses the engineering concept of pollution prevention
and zero waste both at laboratory and industrial scales.
It encourages the use of economical and ecocompatible techniques that not
only improve the yield but also bring down the cost of disposal of wastes at
the end of a chemical process.
3. Principles of Green Chemistry
In 1998, Paul Anastas and John C. Warner published a set of principles to
guide the practice of green chemistry.The twelve principles address a range
of ways to reduce the environmental and health impacts of chemical
production, and also indicate research priorities for the development of
green chemistry technologies.
4. 1) Prevention of by-products:
Preventing waste is better than treating or cleaning up waste after it is
created.
5. 2) Atom Economy:
Synthetic methods should try to maximize the incorporation of all materials used
in the process into the final product.
6. 3) Less hazardous chemical syntheses :
Synthetic methods should avoid using
or generating substances toxic to
humans and/or 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.
7. 4) Designing safer chemicals :
Minimisation of toxicity is made directly
by molecular design.
The principle focuses on choosing
reagents that pose the least risk and
generate only safe by-products.
For eg. : in the manufacture of
Polystyrene, CFC's which contribute to
ozone depletion and global warming are
replaced by CO2.
Johnson & Johnson says it removed DEP,
the phthalate most commonly used in
fragrance.
“Chemical products should be designed to achieve their desired function while being as non-
toxic as possible.”
8. 5) Safer solvents and auxiliaries :
The use of Auxiliary substances(e.g.
solvents, seperation agents, etc.) should
be avoided wherever possible, and
inocuous when used.
The solvent selected for a particular
reaction shouldn't cause any
environmental pollution or hazard(eg.
benzene, alcohol).
Major problem-volatility of
solvents(damages environmement and
human health). To avoid this reactions
are carried in safer green solvents
which maintain the solvency of the
material and are also non-volatile.
9. 6) Design for energy efficiency :
Energy requirements should be minimized, and
processes should be conducted at ambient
temperature and pressure whenever possible.
Developing the alternatives for energy
generation (photovoltaic, hydrogen, fuel cells,
bio based fuels, etc.) as well as continuing the
path toward energy efficiency with catalysis
and product design at the forefront.
10. 7.) Use of renewable feedstocks :
Renewable feedstock are often made from
agriculture products or are the wastes of other
processes; depleting feedstock are made from
fossil fuels(petroleum, natural gas or coal) or are
mined.
for e.g. Substances like CO2(generated from
natural sources) and methane gas (marsh gas) are
considered as renewable starting materials.
“A raw material or feedstock should be renewable rather than depleting
wherever technically and economically practical.”
11. 8.) Reduce derivatives:
Avoid using blocking or protecting groups or any temporary modifications if
possible. Derivative 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 sequence that
eliminate the need for functional group protection should be adopted.
12. 9.) Design for degradation :
“Chemical products should be designed so that at the end of their fuction they
do not persist in the environment and break down into innocuous products”
for e.g.
Chloroflurocarbons(CFCs)
• Do not break down, persist in atmosphere and contributes to
destrution of ozone layer.
DDT
• Insectides 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.
13. 10.) Catalysis :
Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
Use of 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 yeilds:
the hydrogenation of olefins is carried out in the presence of nickel.
2. the reaction becomes feasible in those cases where no reaction is normally possible.
3. Better utilisation of starting material and minimum waste product formation.
14. 11.) Real-time analysis for pollution prevention :
real time analysis for a chemist is
the process of”checking the progrss
of chemical reactions as it happens”
Knowing when your product is “done”
can save a lot of waste, time mand
energy!
15. 12.) Inherently safer chemistry for accident prevention :
“Substances and the form of a
substances used in a chemical process
should be chosen to minimise potential
for chemical accidents, including
releases,explosions, and fires.”
e.g. Dec 3,1984 - poison gas leaked
from a Union Carbide factory, killing
thousands instantly and injuring many
more. Up to 20,000 people have died as
a result of exposure. More than
120,000 still suffer from ailments
caused by exposure.
16. Metrics of Green Chemistry
• Green chemistry metrics are metrics that measure aspects of a chemical
process relating to the principles of green chemistry.
• These metrics serve to quantify the efficiency or environmental
performance of chemical processes, and allow changes in performance to
be measured.
• This, in turn, is likely to aid the communication of research and potentially
facilitate the wider adoption of green chemistry technologies in industry.
Numerous metrics have been formulated over time and their suitability
discussed at great length. A general problem observed is that the more accurate
and universally applicable the metric devised, the more complex and
unemployable it becomes.
17. 1
2
3
Carbon Efficiency : This metric is a good simplification for use in the pharmaceutical
industry as it takes into account the stoichiometry of reactants and products.
Furthermore, this metric is of interest to the pharmaceutical industry where
development of carbon skeletons is key to their work.
Atom Economy : The atom economy calculation is a very simple representation of
the “green-ness”of a reaction as it can be carried out without the need for
experimental results. However, it is useful as a low atom economy at the design
stage of a reaction prior to entering the laboratory can drive a cleaner synthetic
strategy to be formulated.
Reaction Mass Efficiency : Like carbon efficiency, this measure shows the “clean-
ness” of a reaction but not of a process, for example, neither metric takes into
account waste produced. For example, these metrics could present a
rearrangement as “very green” but they would fail to address any solvent, work-
up and energy issues arising.
18. Environmental (E) factor : It highlights the waste produced in the process as
opposed to the reaction, thus helping those who try to fulfil one of the twelve
principles of green chemistry to avoid waste production.
4
5 Eco Scale : By calculating the EcoScale, a quick assessment of the "greenness" of
reaction protocols is obtained, and the areas that need further attention are
clearly indicated, which finally can drive improvement of reaction conditions.
20. bb Econoburette:
• Semimicro volumetric
Econoburette(SMVE) is an economized,
risk free and green chemistry instruent,
which performs valuable titration with
microlitre of substances.
• It is an inbulit pipette performing
functions of the pipette and conical
flask.
• The micro level amount of titer and
titrant consume less time in performing
a volumetric titration and prevents more
use of materials.
PART
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21. Survismeter:
• a single apparatus, used for viscosity, ST,
interfacial tension thus discarding viscometer and
stalagmomter for viscosity and surface tension.
• works on R4M4 materials and methods with hghly
precised and accurate experimental results.
• saves electricity, water, manpoweer, chemicals,
laboratory infrastructure, LPG, oxygen
• most excellent model for study of liquid-liquid
interfaces(LLI) of two immiscible solvents.
• safe in handling, sample loading with no hazards
and no discharge of polluting fumes/materialjs.
• occupies minimum laboratory infrastructure.
PART
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