Knowledge

1. GREEN CHEMISTRY
1
Dr. Gurumeet C Wadhawa
Department of Chemistry
Karmaveer Bhaurao Patil ,College
Vashi, Navi Mumbai

2. WHAT IS GREEN CHEMISTRY?
It is better to prevent waste than to clear it up
afterwards.
% Atom economy is the new % yield
The strive towards the perfect synthesis
Benign by design
Environmentally friendly and economically sound.
2

3. 3
Natural processes Chemical processes
(Lab)
Sun light (energy Source) Thermal / Electrical heating
Enzyme Catalyzed Catalysts are used
Highly specific Not specific
pH-7 pH- variable
Room Temperature Temperature Variable
Water is Used As Solvent Organic solvents are used
Exclusive and pure products are
formed
Mixture are obtained
Environmentally Friendly producing
no pollution
Wastes formed Pollute the
environment

4. Scarcityof naturalresourcesoccurdueto theirhugeconsumption
4

5. WHY CHEMICAL MANUFACTURING IS ESSENTIAL ?
5
Requirements of essential commodities on a very large
scale such as:-
Synthetic Fibers
Plastic
Pharmaceuticals
Dyes
Fertilizers
Pesticides

6. FORTHCOMING SITUATION
6

7. WHAT IS GREEN CHEMISTRY?
7
It is better to prevent waste than to clear it
up afterwards.
% Atom economy is the new % yield
The strive towards the perfect synthesis
Benign by design
Environmentally friendly and economically
sound.

8. BENEFITS OF GREEN CHEMISTRY
8
Non-Toxic
Safe
Economical
Atom
Efficient
Sustainable
Simple
Environment
Friendly
Avoid
Waste
Green
Chemistry

9. 9
PREVENTING WASTES
Design experiments to Reduce or
eliminate waste.
Incorporate materials used in a process
into the final product.

10. 10

11. THE 12 PRINCIPLES OF GREEN CHEMISTRY
 Prevention of waste
 Atom Economy
 Less Hazardous Chemical Syntheses
 Design Safer Chemicals
 Safer Solvents and Auxiliaries
 Design for Energy Efficiency
 Use Renewable Feedstocks
 Reduce Derivatives
 Catalysis
 Design for Degradation
 Real-time Analysis for Pollution Prevention
 Inherently Safer Chemistry for Accident
Prevention
11

12. WHAT IS ATOM ECONOMY?
12
A + B P
Reactant Product
+ U
Unwanted Material
Mass of Product
% Atom economy = 100  ----------------------
Mass of Reactants

13. 13
Example
+ 4.5 O2 O
O
O
+ 2 CO2 + 2H2O
78 144
98
98
% Atom economy = 100  -------------- = 44.1%
78 +144

14. ATOM UNECONOMIC REACTIONS
Example:-
14
• Substitution
• Elimination
• Wittig
• Grignard

15. SUBSTITUTION REACTION (ATOM UN-ECONOMIC)
15
H3C
(CH2)4
C
H2
OH
+ SOCl2 H3C
(CH2)4
C
H2
Cl
+ SO2 + HCl
102 119 120.5
64 36.5
120.5
% Atom economy = 100  --------- = 54.5%
102+119
SO2 and HCl are unwanted by products reducing the overall
atom economy.

16. SUBSTITUTION REACTION
(ATOM UN-ECONOMIC)
16
120.5
% Atom economy = 100  ----------- = 54.5%
102+119
SO2 and HCl are unwanted by products reducing the overall atom
economy.
H3C
(CH2)4
C
H2
OH
+ SOCl2
H3C
(CH2)4
C
H2
Cl + SO2 + HCl
102 119 120.5 64 36.5

17. ELIMINATION REACTIONS
17
56
% Atom economy = 100  ----------- = 45.9%
122
H3C
H
C
Br
H2
C CH3 t-BuOK
-HBr
H3C C
H
C
H
CH3
KBr t-BuOK
136
122
56

18. ATOM ECONOMIC REACTIONS
Example:-
18
• Rearrangement
• Addition
• Diels-Alder
• Other Concerted reactions.
( Pericyclic)

19. REARRANGEMENTS
19
Ex. Claisen Rearrangement
O
200O
C
O
H
OH
Product
134
Phenyl allyl ether
( Reactant ) 134
134
% Atom economy = 100  ------ = 100 %
134

20. ADDITION REACTIONS
20
R
R
H
H
+ HBr
R
R
CH3
Br
% Atom Economy = 100%

21. DIELS ALDER REACTIONS
21
+ h
Atom Economy = 100%

22. Solvents and Green
Chemistry…
22

23. WHY ARE REACTIONS PERFORMED USING SOLVENTS?
 To dissolve reactants.
 To slow or increase the rate of reactions.
 To act as a heat sink or heat transfer agent.
 To prevent hot spots and run-away reactions.
23

24. ISSUES WITH ORGANIC SOLVENTS
 Organic solvents are of concern to the chemical
industry because of the sheer volume used in
synthesis, processing, and separation.
 Organic solvents are expensive
 Organic solvents are highly regulated.
 Many organic solvents are volatile, flammable,
toxic, and carcinogenic.
24

25. SOLVENT ALTERNATIVES
Use of solvent less reactions
Use of “non-organic” solvents
Processing technology
25

26. ADVANTAGES TO SOLVENT LESS
ORGANIC REACTIONS
 There is no reaction medium to collect,
purify, and recycle.
 Reaction times can be dramatically
shortened.
 Lowered energy usage.
 Considerable reduction in batch size
volume.
 Less expensive.
26

27. WAYS TO BE SOLVENT-FREE
 Neat – reagents react together in the liquid
phase in the absence of a solvent.
 Solid-state synthesis – two macroscopic
solids interact directly and form a third,
solid product without the intervention of a
liquid or vapor phase.
27

28. “THE USE OF AUXILIARY SUBSTANCES (E.G. SOLVENTS,
SEPARATION AGENTS, ETC.) SHOULD BE MADE UNNECESSARY
WHEREVER POSSIBLE, AND INNOCUOUS WHEN USED”Solvent less reaction:
28
NH2
R
CHO
R'
R''
R'''
N C
H
R' R''
R'''
Solid A Solid B
Solid C (quantitative yield)
H2OGrind

29. 29
R
O
H
R'-NH2
KH2PO4, rt
R N
H
R'
P
O
P(OEt)3
O
O
Solvent free,
Potassium dihydrogen phosphate: an inexpensive reagent for the
solvent-free, one-pot synthesis of α-aminophosphonates
Ratnadeep S. Joshi, and Charansingh H. Gill*
Green Chemistry letters & Reviews ( Accepted-2010)

30. LIMITATIONS
 Not all reactions will work in the absence of
solvent.
 Function of catalysts.
 Exothermic reactions are potentially dangerous.
 Specialized equipment needed for some
procedures.
 If aqueous quench and organic extraction are
performed, this reduces green benefits.
30

31. USE OF NON-ORGANIC SOLVENTS
Ionic liquids
Water
31

32. 32

33. PROPERTIES OF IONIC LIQUIDS
 Good solvents for a wide range of both organic and
inorganic materials.
 Have potential to be highly polar yet
noncoordinating.
 By varying cations and anions, ionic liquids can be
tailored for specific applications.
 Possibility for reaction rate enhancement, higher
selectivity and higher yields.
33

34. PROPERTIES OF IONIC LIQUIDS
 High thermal stability
 Often immiscible with organic solvents and/or water
 No measurable vapor pressure
 Non-flammable
 Can be recycled
 Are they safer than solvents?
34

35. IONIC LIQUIDS HAVE BEEN USED AS
SOLVENTS IN A VARIETY OF REACTIONS
 Heck Reaction
 Friedel-Crafts reactions
 Diels-Alder reactions
 Hydrogenation reactons
35

36. OTHER APPLICATIONS OF IONIC LIQUIDS
 As biphasic systems in combination with organic
solvent or water in extraction and separation
technologies.
 For catalyst immobilization and recycling.
 As electrolytes in electrochemistry.
36

37. LIMITATIONS OF IONIC LIQUIDS
 Very expensive compared to organic solvents (100
to 1000 x).
 Have to be made, often using solvent.
 Products have to be extracted from ionic liquid
using solvent.
 May have to wash with water prior to reuse.
37

38. ORGANIC REACTIONS IN AQUEOUS MEDIA
 Water–Isn’t that bad
for my organic
reaction?
38

39. ORGANIC REACTIONS IN AQUEOUS MEDIA
 Most of the world’s chemistry occur in aqueous
media.
39

40. WHY WATER?
 Cost - water is the world’s cheapest solvent.
 Safety – doesn’t get any safer than water.
 Some reactions work better in water.
40

41. GREEN CONCERNS OF WATER
 The product may need to be extracted into an
organic solvent to purify it.
 This generates aqueous effluent containing solvent,
which must be properly disposed.
41