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GREEN CHEMISTRY

Dr. Suresh S. Patil

Head, Dept. of Chemistry

SMDBS College, Miraj

Dist. Sangli (Maharashtra)

Email: sanyujapatil@yahoo.com

sanyujaspatil@gmail.com

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Need of Green Chemistry

Chemistry is unquestionably a very important part of our daily lives.

Chemical developments also bring new environmental problems and harmful side effects, which result in the need for ‘greener’ chemical products.

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Green Chemistry Is About...

Cost

^Waste

^Materials

^Hazard

^Risk

Energy

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Adverse Effects of Some Chemicals

DDT [dichloro diphenyl trichloroethane], highly chlorinated insecticides, bioaccumulates in birds, causing eggshell thinning, nesting failures and dramatic population declines of ospreys, eagles and brown pelicans.

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Adverse Effects of Some Chemicals

Thalidomide was used by pregnant women in Europe to lessen the effects of nausea and vomiting during pregnancy ('morning sickness').
About 10,000 children born world-wide with acute birth defects, in many cases in the form of missing or grossly deformed limbs.

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Adverse Effects of Some Chemicals

Chlorofluorocarbons were developed as safer alternatives to sulfur dioxide and ammonia as refrigerants. They cause the destruction of the stratospheric ozone layer.

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Adverse Effects of Some Chemicals

Methyl isocyanate (40 tons) escaped from a pesticide plant into a densely populated area of Bhopal, India in December 3, 1984, causing 3,500 deaths and 1,50,000 injuries.
Dioxin causes various environmental problems.

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Adverse Effects of Some Chemicals

Tetraethyl lead was used as an antiknock additive for gasoline until it was learned that it was causing lead poisoning and lowering of IQ's in children.

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Human society is constantly facing such environmental issues and problems, air pollution, global climate change, soil and water pollution, acid rain, depletion of natural resources and accumulation of natural hazardous waste.
Green chemistry preventing pollution and sustaining the earth.

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Green Chemistry or environmentally benign chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.
The Goal is to make reactions safer, more efficient, and more cost effective while minimizing personal and environmental
harm.
Minimize:

waste
energy use
resource use (maximize efficiency)

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Green Chemistry means

1. Minimize energy use

2. Maximize the incorporation of all starting materials used into the final product (Atom Economy).

3. Develop procedures that can be performed

on an open bench top.

4. Generate products and by-products can be recycled or reused

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Green Chemistry means

6. Use of Catalysts in place of Reagents

7. Use of Non-Toxic Reagents

8. Replace hazardous reagents with safer renewable

reagents

9. Minimize or eliminate the generation of hazardous waste and products

10 Avoid auxiliary substances, such as solvents,

whenever possible.

11. Use reagents catalytically rather than

toichiometrically

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Chemists Must Place a Major Focus on the Environmental Consequences of Chemical Products and the Processes by which these Products are made.

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12 Principles of Green Chemistry

1. 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

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1. Prevention

It is better to prevent waste than to treat or clean up waste after it is formed.
Any process that generates waste demands separation, treatement and disposal. This involves cost, labour, time and space. Hence it this needs to be avoided.

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Increasing Greenness

Prevention & Reduction

Recycling & Reuse

Treatment

Disposal

Waste

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It is better to prevent waste than to treat or clean up waste after it is formed.�

Chemical

Process

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Love Canal�

In Niagara Falls, A chemical and plastics company had used an old canal bed as a chemical dump from 1930s to 1950s. The land was then used for a new school and housing track. The chemicals leaked through a clay cap that sealed the dump. It was contaminated with at least 82 chemicals (benzene, chlorinated hydrocarbons, dioxin). Health effects of the people living there included: high birth defect incidence and siezure-inducing nervous disease among the children.

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Cuyahoga River – Cleveland, Ohio�

There were many things being dumped in the river such as: gasoline, oil, paint, and metals. The river was called "a rainbow of many different colors".
Fires erupted on the river several times before June 22, 1969, when a river fire captured national attention when Time Magazine reported it.

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2. Atom Economy

Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.

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Epoxidation of an alkene using a peroxyacid

Yield = 100%

How many of the atoms of the reactant are incorporated into the final product and how many are wasted?

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Atom Economy

Reagent	Utilized atoms	Wt. of Utilised atoms	Unutilized atoms	Wt. of Unutilised atoms
1. C₈H₈	8C, 8H	104.14	--	0
2. C₇H₅ClO₃	O	16	7C, 5H, Cl, 2O	156.56
Total	8C, 8H, O	120.14	7C, 5H, Cl, 2O	156.56

% AE = [Wt. of atoms utilized /Wt. of all reactants] X 100

= [120.14 / (104.14 + 172.57)] X 100

= 43 %

Atomic Economy is 43%, so 57% of the products are waste

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Inherent Atom Economy

Some Atom Economic Reactions Some Atom Un-Economic Reactions Rearrangement Substitution

Addition Elimination

Diels-Alder Wittig

Other concerted reactions Grignard

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Synthesis of�Acetylsalicylic Acid (Aspirin)

Developed by Felix Hoffman in 1893
Today aspirin is the most widely used medicine of all time.

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Green Synthesis of Aspirin

Reagent made from renewable resource
• Acid catalyst
• No additional solvent
• Absence of fume hood
• Average Percent Yield= 93%
• Atom economy= 75%
• Safe by-product (Acetic Acid)
• Confirmed by IR spectroscopy, melting point, and proton NMR

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�3.Less Hazardous Chemical Synthesis�

Whenever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment

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Polycarbonate Synthesis: Phosgene Process�� Disadvantages :�* Phosgene is highly toxic, corrosive�* Requires large amount of CH₂Cl₂�* Polycarbonate contaminated with Cl � impurities�

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Polycarbonate Synthesis: Solid-State Process��Advantages :�* Diphenyl carbonate synthesized without � phosgene eliminates use of CH₂Cl₂�* Higher-quality polycarbonates

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4. Designing Safer Chemicals

Chemical products should be designed to preserve efficacy of the function while reducing toxicity.

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Antifoulants

Antifoulants are generally dispersed in the paint as it is applied to the hull. Organo tin compounds have traditionally been used, particularly tributyl tin oxide (TBTO). TBTO works by gradually leaching from the hull killing the fouling organisms in the surrounding area

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TBTO and other organo tin antifoulants have long half-lives in the environment (half-life of TBTO in seawater is > 6 months). They also bioconcentrate in marine organisms (the concentration of TBTO in marine organisms to be 104 times greater than in the surrounding water).

Organo tin compounds are chronically toxic to marine life and can enter food chain. They are bioaccumulative.

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5. Safer Solvents and Auxiliaries

The use of auxiliary substances (solvents, separation agents, etc.) should be made unnecessary whenever possible and, when used, innocuous.
In the manufacturing process many auxiliary substances(like solvents, catalysts etc) are employed some of which are toxic and hazardous. So their use must be avoided as far as possible.

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Preferred	Useable	Undesirable
Water	Cyclohexane	Pentane
Acetone	Heptane	Hexane
Ethanol	Toluene	Benzene
Propanol	Isooctane	Diethyl ether
Methanol	Acetonitrile	Dichloromethane
Ethyl acetate	Tetrahydrofuran	Dichloroethane
Butanol	Xylenes	Chloroform
	Acetic acid	DMF
	Ethylene glycol	Pyridine
	DMSO	CTC

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Solventless / Green Solvent Reactions

Microwave method
Grinding Method
Ultrasonic Method
Water as a solvent
New solvents

Ionic liquids
Supercritical fluids

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6. Design for 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.

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Energies in chemical processes

Conventional sources of energy:
Power plant - coal, oil, natural gas

Alternative energy sources:
Photochemical Reactions
Microwave energy
Biomass
Nanoscience & technology
Solar energy
Grinding Method
Ultrasonic Method

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Microwave Synthesizer

Wavelengths between 1 mm and 1 m
Frequency fixed at 2.45 GHz
More directed source of energy
Heating rate of 10°C per second is achievable
Possibility of overheating (explosions)
Solvent-free conditions are possible
Interaction with matter characterized by penetration depth

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Use of Microwave

	Environmentally Thinking	Economically Thinking
Atom Economy	Minimal by-product formation	More from less-incorporate total value of materials
Solvent Reduction	Less solvent waste	Higher throughput, less energy
Reagent Optimization	Catalytic, low stoichiometry, recyclable reagents	Higher efficiency – higher selectivities
Convergency	Due to increased process Efficiency	Higher efficiency – fewer operations
Energy Reduction	from power generation, transport, and use	increased efficiency,shorter process, mild conditions
Safety	Non-hazardous materials reduce risk of exposure, release, explosions and Fires	Worker safety and reduced down time Reduced time on special control measures.

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7. Use of Renewable Feedstocks

A raw material or feedstock should be renewable rather than depleting whenever technically and economically practical.

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Petroleum Products [Hydrocarbons]

Biomaterials [Carbohydrates, Proteins, Lipids]

Highly Functionalized Molecules

Singly Functionalized Compounds [Olefins, Alkylchlorides]

Highly Functionalized Molecules

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Levulinic acid as a platform chemical

DALA (δ-amino levulinic acid)

(non-toxic, biodegradable herbicide)

Diphenolic acid

Acrylic acid

Succinic acid

THF

MTHF

(fuel additive)

butanediol

gamma

butyrolactone

(c) 2010 Beyond Benign - All Rights Reserved.

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Raw Materials from Renewable Resources:�The BioFine Process

Levulinic acid

Municipal solid waste

and waste paper

Agricultural

residues,

Waste wood

Green Chemistry Challenge Award�1999 Small Business Award

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8. Reduce Derivatives

Unnecessary derivatization (blocking group, protection / deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.

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Synthesis of Ibuprofen

Classic Route

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Synthesis of Ibuprofen

Hoechst Route

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9. Catalysis�

Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.

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Heterogeneous vs Homogenous

Distinct solid phase
Readily separated
Readily regenerated & recycled
Rates not as fast
Sensitive to poisons
Lower selectivity
Long service life
High energy process
Poor mechanistic understanding

Same phase
Difficult to separate
Expensive and/or difficult to separate
Very high rates
Robust to poisons
High selectivity
Short service life
Mild conditions
Mechanisms well understood

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Biocatalysts

Enzymes or whole-cell microorganisms
Benefits

Acts at ambient temperture and Pressure
Orientation of site gives high stereospecificity
High Substrate specificity
Acts in aqueous medium as they are Water soluble
They are Naturally occurring
They acts with extremely high speed.
They are non toxic hence harmless to environment.

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Zeolites

They are crystalline alumino-silicates.
Al cab be replaced for B, Fe, Cr, Sb, As, Ga etc.
Silicone can be replaced for Ge, Ti, Zr, Hf etc.
They have number of acid centres hence alternatives for Lewis acids
The acts as Inorganic Cation exchanger
Types depends upon cavity of lattice.
Use of Zeolite change the process from homogeneous to heterogeneous.
Zeolite catalyst can be regenerated.
Can be used at high temperature and pressure.

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Lemon Juice in Organic Transformation as Green Approach

Citrus limonium Citrus aurantium Citrus indica

Citrus limonium

Citrus limonium

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Lemon Juice Catalysed Biginelli Reaction�Synthesis 0f Dihydropyrimidinone

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Comparison with Other Catalyst

Entry	Catalyst	Time	Conditions	Yield (%)
1	p-TSA [23]	1 hr	Reflux in EtOH	90
2	ZnCl₂[20]	30 sec	MW Irradiation	94
3	Zn(BF)₄[25]	4 hrs	Stirring at RT	71
4	Y(OAC)₃ [17]	4½ hrs	115⁰C	89
5	Mg(NO₃)₂[10]	45 min	Refluxed	90
6	CaCl₂[16]	2 hrs	Reflux in EtOH	98
7	InBr₃[14]	7 hrs	Reflux in EtOH	97
8	Pb(NO₃)₂[31]	180 min	Reflux in CH₃CN	89
9	P₂O₅[32]	1.5 hr	Reflux at 100⁰C	94
10	Citric acid [33]	1 hr	80⁰C	79
11	Lemon Juice	2 hrs	Stirring at RT	91

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Why Reaction is Green

Reaction is Multicomponent.
Reaction is ecofriendly as natural catalyst is employed.
Catalyst is obtained from renewable resourse.
Prevents generation of harmful byproducts.
Method in Solventless.
Excess Catalyst can be removed completely by washing with water.
Small quantity of catalyst gives high yield.
Reaction is carried out at ambient temperature which saves the energy.
Cost of Catalyst is very low hence method is Economic.

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Egg Shell Used as Green Catalyst

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Synthesis of 4H-chromenes�

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Proposed Mechanism

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Why Eggs Shell is �Green Catalyst

Reaction is Multicomponent.
Reaction is ecofriendly as natural catalyst is employed.
Catalyst is obtained from renewable resourse.
Prevents generation of harmful byproducts.
Water is used as Green Solvent.
Catalyst can be recycled.
Small quantity of catalyst gives high yield.
Reaction is carried out at ambient temperature which saves the energy.
Cost of Catalyst is very low hence method is Economic.

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Compares with Other Solvents

Sr. No.	Catalyst	Solvent	Reaction condition	Time Min	Yield
1	TBBDA	EtOH:H₂O (1:1)	RT Stirring	120	92
2	PBBS	EtOH:H₂O (1:1)	RT Stirring	150	50
3	NaHCO₃	Water	RT Stirring	--	99.8
4	Al₂O₃	2.5gm	RT Stirring	30	84
5	NH₄OAc	MeOH	Stirring at 0 - 5⁰C	120	--
6	CES	water	RT Stirring	90	92

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Mollusc Shell Used as �Green Catalyst

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Schiff bases synthesis

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Proposed Mechanism

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Why Mollusc Shell is �Green Catalyst

Reaction is ecofriendly as natural catalyst is employed.
Catalyst is obtained from west renewable recourse.
Prevents generation of harmful byproducts.
Water is used as Green Solvent.
Catalyst can be recycled.
Small quantity of catalyst gives high yield.
Reaction is carried out at ambient temperature which saves the energy.
Cost of Catalyst is very low hence method is Economic.

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10. Design for Degradation

Chemical products should be designed so that at the end of their function they do not persist in the environment and instead break down into innocuous degradation products.

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Chlorofluorocarbons (CFCs)Do not break down, persist in atmosphere and contribute to destruction of ozone lay.
DDT Bioaccumulate and cause thinning of egg shells
Degradation of Polymers

Polylactic Acid (PLA)

Manufactured from renewable resources : Corn or wheat; agricultural waste in future.
Uses 20-50% fewer fossil fuels than conventional plastics.
PLA products can be recycled or composted.

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Poly lactic acid (PLA) for plastics production

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Polyhydroxyalkanoates (PHA’s)

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11. Real-time Analysis for Pollution Prevention�

Analytical methodologies need to be further developed to allow for real-time in-process monitoring and control prior to the formation of hazardous substances.

Knowing when your product is “done” can save a lot of waste, time and energy!

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Real time analysis for a chemist is the process of “checking the progress of chemical reactions as it happens.”

Knowing when your product is “done” can save a lot of waste, time and energy!

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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.

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��Lemon juice catalyzed� Knoevenagel Condensation �

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Compares with other catalysts

No.	Catalyst	Solvent	Time	Condition	Yield (%)
1	USY Zeolite	Benzene	12 hr.	Reflux	92
2	AlPO₄-Al₂O₃	--	¼ hr.	Stirr at RT	80
3	LaCl₃.7H₂O	--	1 hr.	Heatat 80⁰C	95
4	I₂/K₂CO₃	EtOH/DMF	12 min	RT	80
5	CTMAB	Water	1.5 hr.	Stirr at RT	90.6
6	TEBA	--	10 min	Ground at RT	90
7	NH₄OAc	--	6 min	MW (850W)	80
8	H₃PW₁₂O₄₀	Water	15 min	Refluxed	91
9	NaF & LiCl	--	1 min	MW	96
10	MgBr₂.OEt₂	TEA, THF	1-2 hr.	Stirr at RT	98
11	Lemon Juice	--	2 hr.	Stirr at RT	91

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Ecofriendly as use of natural catalyst.
Catalyst is obtained from renewable recourse.
Prevents generation of harmful byproducts.
Method in Solvent less.
Excess Catalyst can be removed completely by washing with water.
Small quantity of catalyst gives high yield.
Reaction is carried out at ambient temperature which saves the energy.
Cost of Catalyst is very low hence method is Economic.

Why Lemon Juice is Green Catalyst

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ACETYLATION OF PRIMARY AMINE �(Preparation of acetanilide)

Conventional Procedure:

Alternative Green Procedure:

Green Context:

Avoids use of acetic anhydride (usage banned in some states, due to its utility in narcotic business)
Minimizes waste by-products
Avoids hazardous solvent

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BASE CATALYZED ALDOL CONDENSATION � (Synthesis of dibenzalpropanone)

Conventional Procedure:

Alternative Green Procedure:

Green Context:

Hazardous organic solvents are avoided.
Lithium hydroxide is easy to handle as it is comparatively less hygroscopic than other alkali metal hydroxide.
Use of catalytic amount of the base.

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HALOGEN ADDITION TO C=C BOND � (Bromination of trans-stilbene)

Conventional Procedure:

Alternative Green Procedure:

Green Context:

Corrosive liquid bromine is avoided Atom efficient
Water is the only byproduct in HBr- H₂O₂ method and in NaBr- NaBrO₃ method sodium acetate is formed along with water.
HBr-H₂O₂ mixture and bromide-bromate couple offer in situ oxidation of Br- to molecular bromine.

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[4+2] CYCLOADDITION REACTION�(Diels-Alder reaction between furan and maleic acid)

Conventional Procedure:

Alternative Green Procedure:

Green Context:

Reaction carried out in aqueous medium avoiding benzene Efficient at room temperature itself
100% atom efficient

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REARRANGEMENT REACTION - III �(Benzil Benzilic acid rearrangement)

Conventional Procedure:

Alternative Green Procedure:

Preparation of Benzilic Acid in Solid State under Solvent-free Condition

Green Context:

Solvent-free procedure
Atom efficient

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Thank You.