chemistry of green and technology

1. GREEN CHEMISTRY
UNIVERSITY COLLEGE OF TECHNOLOGY
OSMANIA UNIVERSITY
HYDERABAD-500 007

2. CONTENTS:
 INTRODUCTION
 PRINCIPLES OF GREEN CHEMISTRY
 MICROWAVE ASSISTED REACTIONS
 ULTRASOUND ASSISTED REACTIONS
 CONTINUOUS FLOW REACTORS

3. INTRODUCTION:
 Green chemistry is also known as clean chemistry or benign and
sustainable chemistry.
 Green chemistry is the utilization of a set of principles that reduces or
eliminates the use or generation of hazardous substances in the
design, manufacture and application of chemical products.
 It applies across the life cycle of a chemical product, including its
design, manufacture, use, and ultimate disposal
 Paul Anastas and John Warner, who defined green chemistry as the
design of chemical products and processes that reduce or eliminate
the use and generation of hazardous substances.
• Chemical developments also bring new environmental problems and
harmful unexpected side effects, which result in the need for ‘greener’
chemical products.

4. CONT……….
“Green chemistry is the design of chemical products and processes that reduce
or eliminate the generation of hazardous substances.”
Categorizing hazardous waste
• Ignitability, or something flammable.
•Corrosivity, or something that can rust or decompose.
•Reactivity, or something explosive.
•Toxicity, or something poisonous

5. HISTORY:
• 1962- Rachel Carson wrote scientific book, Silent Spring. It outlined the
devastation that chemicals had on local ecosystems and inspired modern
environment movement.
• 1970- Richard Nixon established the U.S Environmental Protection Agency
(EPA).Its first major decision was to ban the use of DDT and other chemical
pesticides.
• 1990-The Pollution Prevention Act passed
• 1991- Paul T. Anastas coined term Green Chemistry
• 1998 - “Twelve Principles of Green Chemistry” is published by Paul Anastas (of
the EPA) and John

6. PRINCIPLES OF GREEN CHEMISTRY
 1. Prevent waste
 2. Atom Economy
 3. Less Hazardous Chemical Synthesis
 4. Designing Safer Chemicals
 5. Use safer Solvents /reaction conditions
 6. Increase Energy Efficiency.
 7. Use of Renewable Feedstocks
 8. Reduce chemical derivatives
 9. Use catalysts
 10. Design for Degradation
 11. Real-time Analysis for Pollution Prevention.
 12. Inherently Safer Chemistry for Accident Prevention

7. CONT…………
1.Prevent Waste:
It is better to prevent waste than to treat or clean up waste after it has been
created. Prevention principle, is the most important and the other principles are
the “how to” to achieve it.
2. Atom Economy:
Atom economy (atom efficiency) describes the conversion efficiency of a
chemical process in terms of all atoms involved (desired products produced)

8. CONT……
2.ATOM ECONOMY:
 Choose transformations that incorporate most of the starting materials into
the product increases the efficiency and minimizes waste.

9. CONT………..
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
Disadvantages
•phosgene is highly toxic, corrosive
•requires large amount of CH2Cl2
•polycarbonate contaminated with Cl impurities

10. CONT………..
Polycarbonate Synthesis: Solid-State Process
Advantages
•diphenylcarbonate synthesized without phosgene
 eliminates use of CH2Cl2
•higher-quality polycarbonates

11. CONT…………….
4.Designing Safer Chemicals:
Chemical products should be designed to effect their desired function while
minimising their toxicity.
 Antifoulants are generally dispersed in the paint as it is applied to the hull.
 Organotin compounds have traditionally been used, particularly particularly
tributyltin oxide (TBTO).
 TBTO works by gradually leaching from the hull killing the fouling organisms in
the surrounding area
 Organotin compounds are chronically toxic to marine life and can enter food
chain. They are bioaccumulative.

12. CONT………..
5. USE SAFER SOLVENTS/REACTION CONDITIONS
 The use of auxiliary substances (e.g., solvents, separation
agents, etc.) should be made unnecessary wherever possible
and, innocuous when used.
 The object is to choose solvents that make sense chemically,
reduce the energy requirements, have the least toxicity, have
the fewest life cycle environmental impacts and don't have
major safety impacts.

13. CONT………..
6. INCREASE 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.
 Energy—like thinking about how to arrange a synthesis to have the fewest
number of steps, or use the lowest cost starting materials or any other aspect
of interest to the synthetic or process chemist—is just another design
parameter.

14. CONT………..
7. USE OF RENEWABLE FEEDSTOCK:
 A raw material or feedstock should be renewable rather than depleting whenever technically
and economically practical.

15. CONT………..
8. Reduce Derivatives
Unnecessary derivatization (use of blocking groups, protection/de-protection, and
temporary modification of physical/chemical processes) should be minimized 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.

16. CONT……….
9.Use Catalysts:
A catalyst is defined as “a substance that changes the velocity of a
reaction without itself being changed in the process”. It lowers
the activation energy of the reaction but in so doing it is not
consumed.
This means that it can be used in small amounts and can be
recycled indefinitely, that is it doesn’t generate any waste.
For example:- Reduction of a ketone to the corresponding
secondary alcohol using sodium borohydride or molecular hydrogen
as the reductant.

17. CONT……….
10. Designing of degradable products
 Chemical products should be designed so that at the end of their function
they break down into innocuous degradation products products and do not
persist persist in the environment.
 Biodegradation, hydrolysis, and photolysis can be designed into chemical
products.
11.Analyze in Real Time to Prevent Pollution
Analytical methodologies need to be further developed to allow for Real-time,
in-process monitoring and control prior to the formation of hazardous substances.

18. CONT………..
 The effective application of process analytical chemistry directly contributes
to the safe and efficient operation of chemical plants worldwide.
12. INHERENTLY SAFER CHEMISTRY FOR
ACCIDENT PREVENTION:
 Substance and the form of a substance used in a chemical process should be
chosen so as to minimize the potential for chemical accidents, including
releases, explosions, and fires.

19. Microwave assisted Reaction: An
approach to green Chemistry
•Microwave assisted organic synthesis is defined as the preparation of desired
organic compound from available starting material via some procedure involving
microwave irradiation.
•As it is less hazardous it is a potential tool of green chemistry.
•Microwave Synthesis opens up new opportunities to the synthetic chemist in the
form of new reaction that are not possible by conventional heating.
•It is an enabling technology for accelerating drug discovery and development
processes.

20. MICROWAVE IRRADIATION:
•Microwave radiation is non-ionizing form of energy that does not alter the molecular
structure of compounds and provides only thermal activation.
•This phenomenon is dependent on the ability of a specific material to absorb microwave
energy and convert into heat.
•The principle of microwave heating is that the energy can be applied directly to the sample
rather than conductively via the vessel. Heating can be started or stopped instantly
•A Microwave is a form of electromagnetic energy that falls at lower frequency at the end of
electromagnetic spectrum (300 to 300000MHz).
•It is present between infrared radiation and radio waves.
•Microwave uses EMR that passes through material and causes oscillation of molecules which
produces heat.

22. MERITS:
• Higher temperatures
•Faster reactions, lesser by products, pure compounds.
•Absolute control over reaction parameters
•Selective heating
•Energy efficient, rapid energy transfer
•Easy access to high pressure performance
•Does things that can’t be done conventionally.
• Rapid synthesis results in lesser evaporation of solvents

23. DEMERITS :
•In microwave synthesis sudden increase in temperature may led to the
distortion of molecules which may lead to distortion of the reaction.
•Reactions are very vigorous and which may be hazardous.
•Short reaction period ,so care must be taken during the process. •Microwave
reactors are expensive and very delecatated so there must be a care to be taken
during their use.
•Many other things like, temperature sensitive reactions, reactions involving
bumping of material, reaction which effervescences and colour reaction are not
be done in microwave reactor.

24. MECHANISM OF MICROWAVE DI ELECTRIC
HEATING:
•Generation of thermal energy in a non conducting material by the application of
an electromagnetic force.
•wasted energy appears as heat called di- electric loss .
•The non-metallic material with poor thermal conductivity can be very
effectively heated by dielectric heating.
•Dielectric loss is proportional to frequency and square of the supply voltage.
Microwave dielectric heating mechanisms are of 2 types
1. Dipolar polarization mechanism
2. Conduction mechanism

25. CONT………..
DIPOLAR POLARIZATION MECHANISM:
•Interaction of electric field component with the matrix is called DPM.
•For a substance to generate heat when irradiated with micro waves it must
possess a dipole moment, as a water molecule.
•A dipole is sensitive to external electric fields and molecules try to align to an
oscillating field by rotation , the applied field provides the energy for this
rotation.

26. CONT…………
CONDUCTION MECHANISM:
•If two samples containing distilled water and tap water, respectively, are heated
in a single mode microwave cavity at a fixed radiation Power and for a fixed
time, the final temperature will be higher in the tap water sample.
•This phenomenon is due to major interaction of electric field component with
the sample.
 Ions in solution move with applied electric field.

27. EFFECTS OF SOLVENTS IN
MICROWAVE ASSISTED REACTIONS:
 Solvents play a very important role in organic synthesis. One of the most
important characteristics of a solvent is its polarity.
 With microwave heating, this becomes amore significant component, as
microwaves directly couple with the molecules that are present in the reaction
mixture.
 The more polar a reaction mixture is, the greater its ability to couple with the
microwave energy.

28. SOLVENTS:

29. CONT…….

30. REAGENTS:

35. APPLICATIONS:
 Heck reaction
 Suzuki reaction
 Negishi and kumada reaction
 Multicomponent reactions
 Solid phase synthesis
 Reactions in the absence of solvents

36. CONT………

37. CONT……

38. CONT……..

39. CONT……….

40. CONT………..

41. CONT……….

58. Flow chemistry
 The concept of "flow chemistry" defines a very general range of chemical
processes that occur in a continuous flowing stream, conventionally taking
place in a reactor zone.
• The application of flow chemistry relies on the concept of pumping reagents
using many reactors types to perform specific reactions. (piston pump, syringe
pump etc.,)
 Organic synthesis has traditionally been performed in batch process..(RBF,
Test tubes, clossed vessels..)
•Recently continues flow methodologies have gained much attention attention
from synthetic organic chemistry.
•Until a few year ago, continuous flow process were majorly used by
petrochemical & bulk chemical industries and they proved as most economical
method.

59. INSTRUMENTATION:

76. APPLICATIONS:

77. CONT………..

78. CONT…..

79. ADVANTAGES:
 There are well-defined key advantages using flow technologies as
compared to standard batch chemistry methods:
 Scale-up
 Extreme reaction conditions(high/low temperature, high pressure)
 In-line downstream processing
 Automation
 Improved safety (managing hazardous reagents and intermediates)
 Solvent efficiency
 Improved heat transfer
 Improved mass transfer/mixing
 Reproducibility

80. LIMITATIONS:
 In the synthesis of API ;clogging of the reactor happens due to the
precipitation of solids. This is why sophisticated technologies are developed
for the handling of solids.
 Catalytic deactivation
 Future challenge is to accomplish efficient synthesis of enantiomerically pure
product under continuous flow conditions.

81. REFERENCES:
 Green Chemistry: Environmentally Benign ReactionsBook by V. K Ahluwalia
 https://www.slideshare.net/MahendraMahi28/flow-chemistry-96596670
 https://www.slideshare.net/Santachem/green-chemistry-15990119
 https://www.slideshare.net/JoonJyotiSahariah/green-chemistry-ppt-jon
 https://www.slideshare.net/rahulpandit51/microwave-assisted-organic-
synthesis
 https://www.slideshare.net/priyankapriya157/microwave-assisted-organic-
synthesis-89189492
 https://www.slideshare.net/amamun41/ultrasound-in-organic-reaction-and-
supercritical-liquids
 https://www.slideshare.net/MahendraMahi28/flow-chemistry-96596670

83. THANK YOU