Green chemistry principlles and reaction

1. NAME : Vikram singh
M.Sc-3/ paper

2. Contents
• Introduction
• Principles of green chemistry
• Green synthesis
• Examples

3. Introduction
“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.”
Reducing :
1. WASTE
2. MATERIALS
3. HAZARDS
4. RISK
5. ENERGY
6. COST

4. Basic principles of green chemistry
1. Prevention of waste or by products
2. Atom economy
3. Minimization of hazardous products
4. Designing of safer chemicals
5. Safer solvents & auxiliaries
6. Design of energy efficiency
7. Use of renewable product
8. Reduce derivatives
9. Catalysis
10.Designing of degradable products
11.Real-time analysis for pollution prevention
12.Inherently safer chemistry for accident prevention

5. Green reagents
DIMETHYL CARBONATE
Dimethyl carbonate is non-toxic, environment friendly and safe reagent.
Its can be used in several organic synthesis as a green substitute for toxic
Intermediates such as phosgene in carboxylation reaction ,DMS and 𝐶𝐻3𝐶𝑙
in methylation reaction.
It is used for methylation of Sulphones , primary amines , Acrylonitrile and
Methylacrylacetates which are very important in the synthesis of a class of
Anti-depressant drugs
R − CH2 − SO2R′
+ CH3COOCH3 R − CH − SO2R′
+ CH3OH + CO2
CH3
Alkylarylsulphones DMC
K2CO3
AR − NH2 + CH3COOCH3 R − NH − CH3 + CH3OH + CO2
Zeolites
DMC
Aromatic
amine
Limitations : DMC is synthesis from phosgene (toxic).Oxidative carbonylation of Methanol using CO .

6. Polymer supported reagents
Polymer supported reagents are those in which ordinary reagents are bound to polymer support.
Advantage of using this reagents that any excess of reagents can be recovered by using filtration
and used again . Isolation of products is very easy.
E.g. : polymer supported per acid ( Epoxidation of alkene ) , chromic acid , thioanisolyl resin ,
Sulphonazide polymer, polymeric thiomethyl lithium reagents , poly-N-bromosuccinimide etc.
Also used for synthesis of Azo dyes
COOOH
P
C= C
THF
400
C
+
C − C
O
+ COOH
P
4-polymer supported
benzoic per-acid
Epoxide
supported polymer benzoic acid

7. Green catalysts
Acid catalysts
Fluoride silica alumina catalyst,microcapsulated Lewis acid, heterpoly catalyst, zeolite etc.
Used in reaction like Michael addition ,mannich ,iminoaldol etc.
MCSC(𝑂𝑇𝐹)3 = Microcapsulated scandium trifluoro methane sulphonates.
O
Ph
Ph
𝑂𝑆𝑖𝑀𝑒3
𝑂𝑀𝑒
+
+ MCSC(𝑂𝑇𝐹)3
𝐶𝐻3𝐶𝑁 , 𝑅𝑇, 6ℎ
O Ph
Ph
O
𝑂𝑀𝑒

8. Green oxidation catalysts :
• A large number of supported reagents have been used in the liquid phase partial
oxidation of organic substances.
• There has been considerable success in the use molecular sieves ( titanium and
Vanadium) in commercial units.
• The most important application of titanium silicates is the hydroxylation of phenol.
giving mixtures of hydroquinone and catechol.
• The process is clean ,giving excellent conversion to product with very little waste.
TS − I
H2O2
OH OH
OH
OH
OH OH
OH
81%
7% 12%

9. Phase transfer catalysis
• The phase transfer catalysis reaction is methodology for accelerating the reaction between water
insoluble organic compounds and water soluble reactants.
• Basic function of this catalysis is transfer the anion from the aqueous phase to organic phase.
• Advantages : high productivity ,selectivity and ease separation.
Examples : Aliquat 336 ,Benzyltrimethyl ammonium chloride , tetra-N-butyl ammonium chloride
Crown ethers.
𝐶𝐻3(𝐶𝐻3)6𝐶𝐻2𝐶𝑙 + KF
PTC
C16H33P+
(C4H9) 3
Br F
1-Fluoroctane
1-Chloroctane
+ 𝐻2𝑂2
Noyori synthesis
Na2WO4 , Me NHSO4
COOH
HOOC
Adipic acid

10. Biocatalysts
The most important conversion in the context of green chemistry is with the help
of enzymes . Enzymes are referred to as biocatalysts and the transformation are
referred to as biocatalytic conversions.
Oxidoreductases
N
COOH
𝑂2
Achromobacter
xylosoclans N
COOH
OH
Transferases
These enzymes catalysts the transfer of various functional groups .E.g. Transaminase
s
COOET COOET
Baker’s yeast
s

11. Green solvents
Ionic liquids
• Ionic liquids are material that is fluid at ambient temperature is colourless,low volatility & easy
handle.
• These are used as industrial solvents as replacement of volatile organic solvents.
• There used reduce the environmental problems &human health hazards created due to routine
organic solvents
[𝐸𝑇3𝑁𝐻3][𝑁𝑂3] N N
+
Alkyl ammonium
Alkyl phosphonium
E.g.
Applications
𝐻3C
𝐶𝐻3𝐶𝑂𝐶𝑙 𝑒𝑚𝑖𝑛 𝐶𝑙 − 𝐴𝑙𝐶𝑙3
(X=0.67) 5 min,00
𝑐
𝑂

12. Supercritical 𝑐𝑜2
A versatile solvent co2 is used as liquid co2 or supercritical fluids. A gas is naturally converted to
liquid state by increasing the pressure exerted upon it. However, if the substance is place at a
temperature above its critical temperature ( 310
𝐶 𝑓𝑜𝑟 co2) and critical pressure (72.8 atm co2)
supercritical fluid is obtained.
Supercritical liquids have density close to that of the liquid state &viscosity close to that of gaseous
state.
The solvent is non-toxic,inflammable,renewable & in expensive.
E.g. free radical bromination of toluene in presence of supercritical co2.
CH3
+ 400
c h𝑣
co2
CH2Br
N-Bromosuccinimide
toluene Benzyl bromide

13. Solid state reactions
solid phase synthesis
A large number of reaction occurs in solid state without the solvent . Such reactions occur more selective and efficiently .
Halogenation
Crystalline cinnamic acid on bromination gives erythro isomer , but its chlorination gives erythro and threo isomer
𝑋2
Gas-solid C−C
H
X
X
H
−COOH
Michael addition
The number of 2′
− hydroxy − 4′
, 6′
− dimethylchalcones undergo a solid state intramolecular
michael type addition yield to flavones.
𝐻3C
𝐶𝐻3
𝐶𝐻3
𝑂𝐻
𝑂
500
C − 600
C
solid
𝐻3C
𝐶𝐻3
𝑂
𝑂
𝐶𝐻3
Flavones
2′
− hydroxy − 4′
, 6′
− dimethylchalcones

14. Solid supported synthesis
In this reactions ,the reactants are stirred in suitable solvent (for e.g. water, alcohol, methylene chloride
etc. The solution is stirred thoroughly with a suitable absorbent or solid support like silica gel, alumina ,
Phyllosilicate . After the stirring, the solvent is removed the vacuum & the dried solid support on which
the reactants has been support are used for carrying the reaction under microwave irradiation.
𝜆 = 0.01𝑚 − 1𝑚 , 𝜈 = 30𝐺𝐻𝑧 − 0.3𝐺𝐻𝑧
Interaction of matter with these radiation→ ∆ either by collision of charged particle of material or
By conduction or by both .the nonpolar molecule are inert to microwave .
By using water as a solvent
CH3
KMnO4/aqOH
5 min , M.W COOH
85%
Toluene
20-25% yield
10-12 hours
By using very small quantity of organic solvents
OCOCH3
CH3
Al𝐶𝑙3
Chlorobenzene,M.W
OH
CH3
COCH3
60% Yield
4-5 hours
(Fries rearrangement)

15. Microwave assisted synthesis
Microwave normally have the wavelengths between 1cm & 1m.microwave are used for heating purposes.
Microwave heating involve selective absorption of electromagnetic waves by polar molecules; non-polar
molecules are inert to microwave.
Microwave reaction is conducted in a tall beaker , alternatively tellon or polystyrene container can be used.
For domestic microwave oven an excellent solvent N,N-dimethylformamide (DMF) & other hydrocarbon
solvents.For.e.g. hexane,benzene,toluene,xylene.
Synthesis are grouped into three categories :
1.Microwave assisted reaction in water
Hydrolysis
C6H5CH2Cl + H2O C6H5CH2OH
M.W
3 min

16. 2.Microwave assisted reaction in organic solvents
This section include those microwave induced reaction in which one or both the reactants acts as a solvent &
also those reactions in which organic solvents is used to assist the reaction.
C6H5COOH + NC3H7OH Conc H2SO4
M.W ,6 min
C6H5COC3H7
Esterification
3.Microwave solvents for free reactions
It is now possible to carry out reactions without the use of toxic & other solvents. reactants are dissolved in a
suitable solvents like water, alcohol, methylene chloride etc. and the solution are stirred with a suitable absorbent
like silica gel ,alumina .after stirring , the solvent is removed in vacuum and dried solid support on which the
reactants have been adsorbed are used for carrying out the reaction under microwave radiation.
Deacetylation
C6H5CH(OAC)2
Neutral Al2O3
M.W , 40 Sec
C6H5CHO

17. Ultrasound assisted reactions
Electronic energy is converted to the mechanical vibration and produce a sound waves. Sound waves frequency
20KHz-10MHz
Principles:
when ultrasound waves passes through the reaction mixture , small bubbles are formed .this process are
called cavication. When cavication collapse bubbles produces a powerful shockwaves that greatly increases
the temperature and pressure within these tiny regions . under these conditions solvents and reagents suffers
fragmentation to generate reactive species which undergo reaction .the temperature and pressure increase
the rate of reaction.
Cannizaro’s reaction
CHO
Ba(OH)2, EtOH
≫≫≫,10 min
CH2OH
+
COOH

18. THANK YOU