The document discusses microwave assisted reactions for green chemistry. It begins with introducing green chemistry and its focus on reducing hazardous substances. It then discusses how microwave heating allows for faster, more energy efficient reactions by directly coupling with polar molecules. Key advantages of microwave heating include uniform and rapid heating throughout the reaction mixture. This leads to increased reaction rates, higher yields, and less waste generation compared to conventional heating methods. The document provides an overview of the mechanisms of microwave heating and its applications in organic synthesis.

1. GREEN CHEMISTRY
MICROWAVE ASSISTED
REACTIONS
PRESENTING BY- INDRAJIT SAMANTA
ENROLLMENT ID -2022-518-002
M.PHARM; 1 ST YEAR; 2 ND SEMISTER
DEPARTMENT OF PHARMACEUTICAL CHEMISTRY
SCHOOL OF PHAMACEUTICAL EDUCATION & RESEARCH,
JAMIA HAMDARD.
SUBMITTED TO- Dr. GITA CHAWLA
ASSOCIATE PROFESSOR, DEPARTMENT OF
PHARMACEUTICAL CHEMISTRY;
SCHOOL OF PHAMACEUTICAL EDUCATION &
RESEARCH, JAMIA HAMDARD

2. LIST OF CONTENTS
INTRODUCTION OF GREEN CHEMISTRY
MICROWAVE ASSIST REACTION
PROCESS OF INCREASES THE RATES OF REACTION
MECHANISM
SUPERHEATING EFFECT OF MICROWAVES
MERITS & DEMERITS
APPLICATIONS

3. INTRODUCTION:
What is Green Chemistry?
– Sustainable chemistry.
– Chemistry that is benign by design.
– Pollution prevention at the molecular level.
– All of the above.
– Focus on processes and products that reduce or eliminate the use of polluting substances.
-The term green chemistry is defined as “the invention, design and application of
chemical products and processes to reduce or to eliminate the use and generation of
hazardous substances”.

4. WHY DO WE NEED GREEN CHEMISTRY?
Chemical developments bring new environmental problems and harmful
unexpected side effects, which result in the need for ‘greener’ chemical
products. Eg. DDT.
Green chemistry looks at pollution prevention on the molecular scale. It 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.
This program works very closely with the twelve principles of Green
Chemistry

5. THE BENEFITS OF GREEN CHEMISTRY
Economical
Energy efficient
Lowers cost of production and regulation
Less wastes
Fewer accidents
Safer products
Healthier workplaces and communities
Protects human health and the environment

6. 12 PRINCIPLES OF GREEN CHEMISTRY
1. Pollution Prevention
2. Atom Economy
3. Less Hazardous Chemical Synthesis
4. Designing Safer Chemicals
5. Safer Solvents and Auxiliaries
6. Design for Energy Efficiency
7. Use of Renewable Feedstocks
8. Reduce Derivatives
9. Catalysis
10. Design for Degradation
11. Real-time analysis for Pollution
Prevention
12. Inherently Safer Chemistry for
Accident Prevention

7. MICROWAVE ASSISTED REACTIONS
Microwave assisted organic synthesis which is an important tool for green chemistry.
Microwave radiation, an electromagnetic radiation, which is widely use as a source of heating
in organic synthesis. Microwave assisted organic synthesis has emerged as a new “lead” in
organic synthesis which makes the chemistry to go green. This technique has provided the
excellent momentum for many chemists to switch to microwave assisted Chemistry.
The great invention of burner was done in organic chemistry 1899 by Robert Bunsen. This
invention was so useful that it lead to provide heat in a much focused manner required to carry
out any chemical synthesis.

8. MICROWAVE

9. Concept:
Microwave (MW) energy is a form of radiation. The term radiation means that the
energy is transported by the force fields of electromagnetic waves; they can
radiate through a perfect vacuum and do not need any medium to transfer
energy from one object to another.
All electromagnetic waves have two components
1) Electric field
2) Magnetic field

10. WHAT ARE MICROWAVES?
oElectromagnetic energy which lie in electromagnetic spectrum corresponds to wavelength of 1cm to 1m
and frequency of 30GHz to 300MHz .
oThis places it between infrared radiation, which has shorter wavelength in the1-25cm range for radar.
oMicrowaves are used principally in main three areas of drug research:
oThe screening of drug formulae which are made of organic compounds and those candidate
compounds which are seem to be numerous,
oMicrowave-assisted peptide synthesis, in which peptides are used as drug. The synthesis of long chains
of peptides is very difficult but microwave approach has been especially effective in the area of peptides
synthesis.
oThe microwave-assisted DNA amplification which is used in disease analysis where there are a number
of DNAs which are very difficult to process

11. Advantages:
Uniform heating occurs throughout the
material
Process speed is increased
High efficiency of heating
Reduction in unwanted side reaction
Purity in final product
Improve reproducibility
Environmental heat loss can be avoided
Disadvantages:
Heat force control is difficult.
Closed container is difficult because it could
burst
In-situ monitoring
Expensive setup

12. HOW DOES A MICROWAVE TURN
ELECTRICITY INTO HEAT?
1. Inside the strong metal box, there is a microwave generator called a magnetron. When you start
cooking, the magnetron takes electricity from the power outlet and converts it into high-powered, 12cm
(4.7 inch) radio waves.
2. The magnetron blasts these waves into the food compartment through a channel called a wave
guide.
3. The food sits on a turntable, spinning slowly round so the microwaves cook it evenly.
4. The microwaves bounce back and forth off the reflective metal walls of the food compartment, just
like light bounces off a mirror. When the microwaves reach the food itself, they do not simply bounce
off. Just as radio waves can pass straight through the walls of your house, so microwaves penetrate
inside the food. As they travel through it, they make the molecules inside it vibrate more quickly.
5. Vibrating molecules have heat so, the faster the molecules vibrate, the hotter the food becomes.
Thus, the microwaves pass their energy onto the molecules in the food, rapidly heating it up.

13. INCREASED REACTION RATES
Reaction time is reduced from hours to minutes when assisted by microwaves. Under microwave
irradiations, high and intense temperature can be achieved very quickly and liquids are super-heated.
According to Arrhenius equation, K=A exp (-ΔG°/RT), a simple rule is that higher is the temperature,
higher is the reaction rate.
Compared to conventional heating, microwave heating enhances the rate of certain chemical reactions
by 10 to 1,000 times. This is due to its ability to increase the temperature of a reaction, for instance,
synthesis of fluorescein, which usually takes about 10 hours by conventional heating methods, can be
conducted in only 35 minutes by means of microwave heating.
In certain chemical reactions, microwave radiations produces higher yields compared to conventional
heating methods, for example, microwave synthesis of aspirin results in an increase in the yield of the
reaction, from 85% to 92%.

14. CONVENTIONAL HEATING vs MICROWAVE
HEATING
CONVENTIONAL HEATING
a. Reaction mixture heating proceeds from a surface usually
inside surface of reaction vessels.
b. The vessel should be in physical contact with surface
source that is at a higher temperature source.
c. Heating mechanism involve conduction.
d. By thermal or electric source heating take place.
e. Heating rate is less.
MICROWAVE HEATING
a. Reaction mixture heating proceeds directly inside mixture.
b. No need of physical contact of reaction with the higher
temperature source. While vessel is kept in microwave cavities
c. Heating mechanism involve dielectric polarization and
conduction.
d. By electromagnetic wave heating take place.
e. Heating rate is several fold high

15. MICROWAVE ASSISTED
REACTIONS
 Microwave irradiation has gained popularity in the past decade as a powerful tool for rapid and
efficient synthesis of a variety of compounds because of selective absorption of microwave energy
by molecules.
This phenomenon is dependent on the ability of a specific material to absorb microwave energy
and convert it into heat. Microwave passes through material and causes oscillation of molecule
which produces heat.
Microwave heating produces heat in the entire material in the same rate and at the same time at a
high speed and at a high rate of reaction.
Microwave heating is the best process due to the microwave couple directly with the molecule
that are present in the reaction mixture, leading to fast rise in temperature, faster reaction and
cleaner chemistry.
The microwave chemistry is also called as Green Chemistry because it does not produce any
hazardous material like gas, fumes, heating etc.

16. MECHANISM OF MICROWAVE HEATING
All the materials are not susceptible to microwave heating as response of various materials to
microwave radiation is diverse.
Microwave absorbing materials (e.g. water) are of utmost important for microwave chemistry
and three main different mechanisms are involved for their heating namely:
Dipolar polarization
Conduction mechanism
Interfacial polarization.

17. Principles Of Microwave Heating
DIPOLE INTERACTION
Polar ends of a molecule tend to align themselves
oscillate in step with the oscillating electrical field of
microwaves. Collisions and friction between the
molecules result in heating.
For a substance to be able to generate heat when
irradiated with microwaves it must be a dipole, i.e. its
molecular structure must be partly negatively and
positively charged. Since the microwave field is
the dipoles in the field align to the oscillating field. This
alignment causes rotation, which results in friction and
ultimately in heat energy.
IONIC CONDUCTION
It results if there are free ions or ionic species
present in the substance being heated. The electric
field generates ionic motion as the molecules try to
orient themselves to the rapidly changing field. This
causes the instantaneous super heating.
During ionic conduction, dissolved (completely)
charged particles (usually ions) oscillate back and
forth under the influence of microwave irradiation.
This oscillation causes collisions of the charged
particles with neighboring molecules or atoms, which
are ultimately responsible for creating heat energy.

18. Principles Of Microwave Heating
INTERFACIAL POLARIZATION:
The interfacial polarization method can be considered as a combination of both the
conduction and dipolar polarization mechanisms. It is important for heating systems that
comprise a conducting material dispersed in a non-conducting material.

19. MECHANISM
1. Heating with microwave frequency involves primarily two mechanisms dielectric
and ionic.
2. Water in the food is often the primary component responsible for dielectric
heating.
3. Due to their dipolar nature, water molecules try to follow the electric field
associated with electromagnetic radiation as it oscillates at the very high
frequency.
4. Such oscillation of trip molecules produces heat.
5. The second major mechanism of heating with microwave frequency is through
the oscillatory migration of ions in the food that generate heat under the influence
of the oscillating electric field.

20. MECHANISM
6. Kinetic energy is actually imparted to the ions by the electric field so that the field is
alternating rapidly heat.
7. Microwaves penetrate materials and release their energy in the form of heat as the polar
molecules (ones with positively and negatively charged ends - such as water) vibrate at high
frequency to align themselves with the frequency of the microwave field.
8. The microwaves interact directly with the object being heated.
9. The interaction is related to the chemical properties of the object and it is possible to apply
heat in ways that can not be achieved by conventional means: convection heating, conductive
heating or radiant heating .

21. MICROWAVE GENERATION
The microwaves are generated by special oscillator tubes called "Magnetrons and Klystron”.
These are devices that convert low frequency electrical energy into hundreds and thousands of megacycles.
The electromagnetic energy, at microwave frequency is conducted through a coaxial tube or wave guide at a point of usage.
Both Magnetron and Klystron are electron tubes which generate microwaves.
1. Magnetron: It is a cylindrical diode with a ring of resonant cavities that acts as a anode structure. The cavity is the
space in the tube which becomes excited in a way that makes at a source for the oscillation of microwave energy . The
Magnetron is a vacuum valve in which the electron, emitted by the cathode, turn around under the action of a
continuous electric field produced by the power supply and of a continuous magnetic field. The movement produces
the electro-magnetic radiation.
2 Klystron: It is a vacuum tube in which the oscillation are generated by alternatively slowing down and speeding
upon electron beam. This results in periodic bunching of electrons. Klystron uses the transit time between two given
points to produce this modulated electron stream which then delivers pulsating energy to a cavity resonator and sustain
oscillation within the cavity.

22. SUPERHEATING EFFECTS OF MICROWAVE
Superheating- boiling retardation or boiling delay- a liquid is heated to a temperature higher than
its boiling point, without boiling.
achieved by- heating a homogeneous substance in a clean container, free of nucleation sites,
while taking care not to disturb the liquid.
When a liquid is heated by microwaves, the temperature increases rapidly to reach a steady
temperature while refluxing. It happens that this steady state temperature can be up to 40 K higher
than the boiling point of the liquid.
The bulk temperature of a microwaved solvent under boiling depends on many factors: physical
properties of the solvent, reactor geometry, mass flow, heat flow, and electric field distribution.

23. SUPERHEATING EFFECTS OF MICROWAVE
oBY EXTERNALLY COOLING THE REACTION VESSEL with compressed air , while simultaneously
administering microwave irradiation, more energy can be directly applied to the reaction mixture.
oEnhanced microwave synthesis ensure that a high, constant level of microwave energy is applied.
oSimultaneously cooling enables a greater amount of microwave energy to be introduced into a
reaction while keeping the reaction temperature low.
oResults in greater yields & cleaner chemistry.
oEMS was employed in the synthesis of a variety of alpha-keto amides to support a protease inhibitor
discovery project.
oThis may eventually lead to improved treatment for stroke, Alzheimer, muscular dystrophy.

24. SUPERHEATING EFFECTS OF MICROWAVE

25. GREENNESS OF MICROWAVE SYNTHESIS
oHomogeneity of heating.
oEnergy consumption of the synthesis Speed of heating.
oClean, reproducible and easily automated.
oMicrowave heating is efficiently used to force the organic
chemical reactions!!!
o Under microwave irradiations, high and intense temperature
can be achieved very quickly. According to Arrhenius equation,
K =A∙e(-Ea/R∙T)
omicrowaves oil bath heating mantle Higher temperature =
Higher reaction rate

26. GREENNESS OF MICROWAVE
SYNTHESIS
oLow energy consumption: homogeneity and speed of heating.
oFaster reaction: minutes instead of hours or days (low energy consumption).
oAtom economy: greater yield, lesser wastage.
oGreen solvents: H2O, EtOH, methanol and acetone are strongly responsive to
microwave.
oLess or no solvent: possibility to carried out concentrated reaction. Possibility of neat
condition or supported reagents.
oRapid conditions screening: integrated on-line control guarantees safe operations.

27. MERITS
considered as a more efficient source of
heating than conventional steam (or oil
heated vessels), since the energy is directly
imparted to the reaction medium rather than
through the walls of a reaction vessel
the rapid heating capability of the
microwave leads to considerable saving in
dissolution or the reaction time
The smaller volume of solvent required
contributes to saving in cost and diminishes
the waste disposal problem
 Rapid reactions
 High purity of products
 Less side-products
 Selective heating
 Improved yields
 Simplified and improved synthetic
procedure
 Wider usable range of temperature
 Higher energy efficiency
 Sophisticated measurement and safety
technology
 Reproducibility of reactions

28. DEMERITS
Microwave procedures are limited by the presence of solvents which reach their boiling points within a
very short time (~ 1 min) of exposure to microwave
Consequently, high pressures are developed, leading to damage to the vessels material or the microwave
oven itself and may occasionally lead to explosion.
Heat force control is difficult
Water evaporation
Closed container is dangerous because it could be burst

29. LIST OF ORGANIC
REACTIONS CARRIED
OUT BY MICROWAVE IRRADIATION
Reactions in liquid phase :
Diels-Alder, etero- Diels Alder, Alder-Bong reactions Synthesis and hydrolysis of esters and
amides Different aliphatic nucleophilic substitutions Oxidation of alcohol Condensation of
malonic esters Cyclocondensations of various eterocycle compounds Synthesis of
organometallic compounds
Reactions in phase-transfer:
Saponification's of hindered esters, Decarboxylation's
Solvent-free reactions:
Aliphatic nucleophilic substitutions, Hydrolysis of esters and amides, Dehydration of alcohols,
Oxidation of alcohols

30. APPLICATIONS OF MICROWAVE ASSISTED
REACTIONS :
SOME NAME REACTIONS:
1. Heck reaction - It is most important C-C bond forming reaction.
2. Suzuki reaction - It is defined as palladium catalyzed cross coupling of aryl halide with boronic
acids.
3. Negishi and Kumada reaction - It is the coupling of Grignard reagents with alkyl, vinyl or aryl
halides under Ni/Pd catalysis.
4. Multicomponent reactions
5. Ullmann condensation reaction

31. OTHER APPLICATIONS
1. Application of Microwave in material Chemistry - The use of microwave for synthesis of inorganic
solid is very efficient technique in material chemistry. It has been used in preparation of ceramics.
2. Preparation of catalyst under microwave irradiation- Synthesis of a high permeance NaA zeolite
was prepared from an aluminate and silicate sodium in a modified domestic microwave oven.
3. Application of Microwave in polymer synthesis- The synthesis of polyacrylamide was studied under
microwave irradiation. PAM is used as a flocculating agent in waste water treatment .
4. Analytical Chemistry- Microwave irradiations are routinely used for sample digestion, solvent
extraction, gravimetric and moisture determination techniques.
5. Microwave irradiation in waste management- Microwave heating can be advantageously used for
waste management in areas where human exposure can cause health problems.

32. LABORATORY MICROWAVE

33. INDUSTRIAL MICROWAVE REACTION

34. REFERENCES:
S. Ravichandran and E.Karthikeyan, Microwave Synthesis - A Potential Tool for Green Chemistry, International Journal of ChemTech
Research, CODEN( USA): IJCRGG ISSN : 0974-4290, Vol. 3, No.1, pp 466-470, Jan-Mar 2011.
Wanisa Abdussalam-Mohammed, Amna Qasem Ali, Asma O. Errayes, Green Chemistry: Principles, Applications, and
Disadvantages, 01 July 2020, DOI: 10.33945/SAMI/CHEMM.2020.4.4
Pham Thi Phan et al, The Properties of Microwave-Assisted Synthesis of Metal–Organic Frameworks and Their Applications, 15
January 2023, 13, 352, https://doi.org/10.3390/nano13020352.
Madhvi A. Surati, Smita Jauhari, K. R. Desai, A brief review: Microwave assisted organic reaction, 2012, 4 (1):645-661
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Gangrade D, Lad SD, Mehta AL, Overview on microwave synthesis – Important tool for green Chemistry, 28-06-2015, 37 – 42.
Ajmer Singh Grewal et al, MICROWAVE ASSISTED SYNTHESIS: A GREEN CHEMISTRY APPROACH, 2013; 3(5):278-285, ISSN:
2277-4149.
 Ravichandran S. and Karthikeyan E. Microwave synthesis-A potential tool for Green Chemistry. International Journal of
ChemTech; Research.Jan,March-2011;3(1):466-470.

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