GREEN CHEMISTRY AND GREEN SYNTHESIS

GUIDED BY PRESENTED BY P.PAPUNAIDU(156913)

DEPARTMENT OF CHEMISTRY

Green Chemistry = Responsibility“Because chemistry is the science that introduces new substances into the world and we have a responsibility for their impact in the world.” -Ronald Breslow

What is green chemistry Green Chemistry is the utilisation 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

Green Chemistry Is About...

Cost

Waste

Materials

Hazard

Risk

Energy

Some Aspects of Green Chemistry

1.Prevention It is better to prevent waste than to treat or clean up waste after it has been created.

2.Atom Economy Synthetic methods should be designed to maximise the incorporation of all materials used in the process into the final product.

3.Less Hazardous Chemical Synthesis Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to people or the environment.

4.Designing Safer Chemicals Chemical products should be designed to effect the desired function while minimising their toxicity

The 12 Principles of Green Chemistry

5.Safer Solvents and Auxiliaries The use of auxiliary substances (e.g., solvents or separation agents) should be made unnecessary whenever possible and innocuous when used. 6.Design for Energy Efficiency Energy requirements of chemical processes should be recognised for their environmental and economic impacts and should be minimised. If possible, synthetic methods should be conducted at ambient temperature and pressure.

7.Use of Renewable Feed stocks A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.

The 12 Principles of Green Chemistry

The 12 Principles of Green Chemistry

8.Reduce Derivatives Unnecessary derivatization (use of blocking groups, protection/de-protection, and temporary modification of physical/chemical processes) should be minimised or avoided if possible, because such steps require additional reagents and can generate waste.9. Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.

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

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.

12. Inherently Safer Chemistry for Accident Prevention Substances and the form of a substance used in a chemical process should be chosen to minimise the potential for chemical accidents, including releases, explosions

The 12 Principles of Green Chemistry

GREEN SYNTHESIS

“It is better to prevent waste than to treat or cleanup waste after it is formed”

ChemicalProcess

Preparation of ibuprofen

• Ibuprofen was synthesized in 1960 by the pharmaceutical company Boot (England). The old synthesis of Ibuprofen was performed in six steps with the formation of secondary by-products and waste.

• In 1990 the company BHC was discovered a new synthetic route with only three steps and increased efficiency.

OHCCOCH3

OEtO2C

AC2O

AlCl3 NaOEt

H2O/H+

NH2OH

HO2C

ClCH2CO2Et

N

N

H

HO

H2O/H+

Old route for the preparation of Ibuprofen

COCH3 HO2CHO

HF

AC2O

H2/Ni CO/Pd

Greener synthetic route of Ibuprofen

Advantages of green synthesis

Old synthesis• final 40% yield

• six steps process

• AlCl3 used as a catalyst but it is not possible to recycled

• High energy required

Green synthesis• final 77% yield

• Three steps process

• Raney nickel catalyst. It can be recycled and reused

Low energy required

Synthesis of Adipic Acid

O

and/or

OH

HO

OH

O

OHNO3

Na2WO4 , H2O2

KHSO4, Aliquat 336

Traditional Route

Greener Route

Adipic Acid

yield 55.7%

yield 65%

HO

OH

O

O

Adipic Acid

Synthesis of Maleic Anhydrite

Yield of the Reaction = 44.4%

Yield of the Reaction = 57.6%.

The “old” Method used as a starting material benzene (C6H6) and a catalyst which was composed of oxides of Vanadium and Molybdenum ,V2O5 and MoO3

2 C6Η6 + 9Ο2 (air) catalysts 2 C4Η2Ο3 + Η2Ο + 4 CΟ2

The “new greener” Method with starting material n-butane and catalyst (VO)2P2O5

C4Η10 + 3.5 Ο2 (air) catalyst C4Η2Ο3 + 4Η2Ο

Different Energy source in green chemistry

Alternative Energy SourcesMicrowaveUltrasoundSunlight / UV

Conventional HeatingBunsen burnerOil bathHeating mantle

Microwave Dielectric Heating Mechanisms

Dipolar PolarizationMechanism

Conduction Mechanism

Dipolar molecules try toalign to an oscillating fieldby rotation

Ions in solution will moveby the applied electricfield

Recent Progress of Green Synthesis

1.Enantioselective Michaell addition2.Oxidation of sulfides with H2O2

5.Borono-Mannich reactions in solvent-free conditions

4.Hydrolysis of benzamide under acidic condition

6.Preparation of Dumb-bell-shaped C120&

3.Transformation of aromatic and aliphatic alcohols in the equivalent carboxylic acids and ketones

1.Enantioselective Michaell addition(H2O)

A highly enantioselective Michael addition of malonates to α,β-unsaturated ketones in water is catalyzed by a primary-secondary diamine catalyst containing a long alkyl chain. This asymmetric Michael addition process allows the conversion of various α,β-unsaturated ketones.

MeO OMe

O O

+O O.2eq.catalyst

0.2eq.TFA

H2O 500C,40-h

O

MeCO2

MeCO2

NH

C10H21NH2

catalyst;

Oxidation of sulfides with 30% hydrogen peroxide catalyzed by tantalum carbide provides the corresponding sulfoxides in high yields, whereas niobiumcarbide as catalyst efficiently affords the corresponding sulfones. Both catalysts can easily be recovered and reused without losing their activity

2.Oxidation of sulfides with H2O2EtOH, 60oc, 1.75-22h

4mol % NbCdiameter; 5 µ m

RS

R'R

SR'

O O

Various aromatic, aliphatic and conjugated alcohols were transformed into the corresponding carboxylic acids and ketones in good yields with aq 70% t-BuOOH in the presence of catalytic amounts of bismuth(III) oxide. This overallmethod green.

5.3. Transformation of aromatic and aliphatic alcohols in the equivalent carboxylic acids and ketones

R OH

5eq.tBuOOH (70%aq.), 0.1eq.BI2O3

EtOAc, r.t.18-55H R OH

O

R= Ar, alkyl,vinyl

4.Hydrolysis of benzamide under acidic condition(M.W)

conventional heating: 1h 90%MW heating: 10m min 99%

C CO NH2

O OH

2O% H2SO4

5.Borono-Mannich reactions in solvent- free conditions(M.w)

Borono-Mannich reactions can be performed in solvent-free conditions under microwave irradition with short reaction time

B(OH)2 CHO

OH

HNR2 OH

Ph

R2N

R=alkyl,Bn

++

MW, 2 h ,1200c

neat

Solid-State Preparation of Dumb-bell-shaped C120

Pd/Al2O3/H2

Con.mw/1000C

Cl

100%con

Conclusion

Green chemistry Not a solution

to all environmental problems But the most fundamental approach to preventing pollution.

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