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Transcript of GREEN CHEMISTRY
The Twelve Commandments of Green Chemistry
Less hazardous chemicals syntheses
Design safer chemicals
Safer solvents and auxiliaries
Design for energy efficiency
Use renewable feedstocks
Design for degradation
Real-time analysis for pollution prevention
Inherently safer chemistry for accident prevention
APPLICATIONS OF GREEN CHEMISTRY-
The production of nylon 6 by the classical process produces ammonium sulfate for every pound of product.
like the traditional nylon 6 process, starts with benzene, which is toxic.
severe oxidation with nitric acid oxidizes cyclohexanol–cyclohexanone mixture to adipic acid. This is the only large scale industrial oxidation requiring this polluting reagent.
Ionic liquids are salts of nitrogen- or phosphorus-containing organic cations coupled with inorganic anions
Because of the asymmetry of the cations and size differencesbetween them and the anions, they do not pack readily into a crystal, and consequentlyare liquids at room temperature.
Ionic liquids, many incorporating docusate are highly lipophilic, some being fully miscible with hydrocarbons. There is also a possible problem in that ionic liquids are usually lipophilic and, as notedabove, lipophiles accumulate in body fat and are not regarded as environmentally.
There are a number of drivers behind the emerging opportunities in green chemicals:
Demand-driven: increasingly demanding safer and more sustainable products.
Cost-driven: Since fossil fue is the fundamental input for all chemical product and the scarcity nas lead to Diversifying the industry’s input base to use more renewable resources will improve risk management and strengthen competitiveness in the long run.
Market creation through innovation: Despite the existence of large corporate play¬ers, global markets for chemical products are generally highly competitive. For sustaining rather than relying on older technologies and standardized products, innovation in the area of green chemistry, with new products creating new market opportunities.
Green chemistrys focuses on the environmental implications of industrial chemical processes.
Green chemistry effi ciently utilizes raw materials, eliminates waste, and avoids the use of toxic and/or hazardous reagents and solvents in the manufactureand application of chemical products.
This incorporated the concepts of atom economy and E factors and
eventually became a guiding principle of Green Chemistry as embodied in the 12 Principles of Green Chemistry
Photocatalysts(industrial flash photolysis) .Research is done for use of UV light in water purification.
Waste water contains tiny quantities of chlorophenols,dioxins, and polychlorobenzenes. Such chlorinated compounds are anathema because,although present in minuscule quantities, they are lipophilic and accumulate in bodyfat.A possible solution is to irradiate the water with UV light over a titanium dioxidephotocatalyst, perhaps loaded with platinum. Water is transparent to UV light.The photoreaction on the titanium dioxide yields hydroxyl ions, which displace thechlorine atoms on the aromatic rings.
One way of reducing the organochlorine compounds would be to reduce paper recycling, butrecycling is a cardinal principle of greenness.
Carbaryl which is a pesticide can be manufactured using phosgene route as well as a non-phosgene route since phosgene is poisonous in nature.
6.LIQUID AND SUPERFICIAL CARBON DIOXIDE
An advantage of liquid or supercritical carbon dioxide is that a large degree of controlover product selectivity and yield is possible by adjusting the temperature andpressure of the reactor.
Disadvantage- achievement of high pressures is expensive and offends one of the “green” commandments
pure supercritical carbon dioxide frequently leads to low reaction rates and inadequatecatalyst solubilities.
This problem has led to the idea of a “CO2-expanded
Sertraline is a pharmaceutical used to treat depression.
The three stages starting from naphthelenone were carried out in a single solvent ethanol without isolating the intermediates.
Titanium tetrachloride was no longer required; due to the poor solubility of imine in ethanol it directly precipitates out.
Result:Overall yield has been nearly doubled to 37%
Paired electrosynthesis seems to be one of the new challenges to start the new millenium. This approach to a sustainable development has lead to its first technical process in the last days of the old century
The new process avoids hydrogenation of phthalic acid anhydride from the beginning.
It avoids not only the energy for the high-pressure hydrogenation process but also all resources needed for hydrogen without any additional electricity demand for the electrolysis.
So this new process is a nice example for electrochemical efforts to a sustainable development.
Paired electrosynthesis of phthalide and tert-butylbenzaldehyde.
Biotechnology : way of using renewable raw materials and producing biodegradable products (for chemists)
Economic problem in harvesting natural products rather than pumping them out of the ground
waste disposal problem in getting rid of the huge amounts of biomass that accompany the biotechnological product
The development of PHA into a branch of bulk chemical industry will address at least three issues:
shortage of petroleum for plastic materials,
reduction of CO2 emissions,
It is related to the sustainable development of the chemical and material industries.
Polyhydroxyalkanoates (PHA), a family of biopolyesters with diverse structures, are the only bioplastics completely synthesized by microorganisms.
this problem has led to the idea of a “CO2-expanded”
FOR AN EXAMPLE LETS TAKE-
2,6-di-tert-butylphenol in acetonitrile may be oxidized to 1,4-benzoquinone in
acetonitrile/supercritical CO2 in a 1:1 ratio with a cobalt (II) catalyst.
Carbon dioxide increases the solubility of oxygen by nearly two orders of magnitude
compared with pure acetonitrile, while the acetonitrile aids catalyst solubility and
allows a rapid catalyst turnover rate. The system will operate at 60–90 bar compared
with the 200 bar required for pure supercritical carbon dioxide, and the catalyst can
be recovered simply by increasing the carbon dioxide pressure until the catalyst precipitates.
1.Replacement of leblanc by solvay process
2.For every kg of phloroglucinol produced ca. 40 kg of solid waste, containing
Cr 2 (SO 4 ) 3 , NH 4 Cl, FeCl 2 , and KHSO 4 , were generated. This process was eventually
discontinued as the costs associated with the disposal of this chromium - containing
waste approached or exceeded the selling price of the product.
Phosgene reacts with methylamine to give methyl isocyanate, which was stored and later reacted with alpha-naphthol to give the pesticide carbaryl.
Phosgene route to carbaryl leads to formation of an intermediate chemical, methyl isocynate which is highly toxic and extremely hazardous to human health.
The use of phosgene was also associated with but not directly implicated in the Bhopal disaster, the worst in the history of the chemical industry.
The highly exothermic hydrolysis of methyl isocynate took place in one of the storage tank on the night of 3 December 1984, leading to Bhopal disaster.
NON PHOSGENE ROUTE
Alpha naphthol reacts with dimethyl carbonate to form an intermediate which is further reacts with methyl amine to carbaryl.
10.Monomethylation by dimethyl carbonate
Methylation by dimethyl carbonate
Dimethyl carbonate's has lower toxicity and it is biodegradable.
Since it is harmless, it can be used in large excess and can serve as a solvent at the same time as a methylating agent.
It avoids formation of undesirable inorganic salts as byproducts.
Dimethyl carbonate is a ''green” methylating agent and, in some reactions, it can replace dimethyl sulfate,methyl chloride, or sodium hydride.
Two examples that have been commercialized
are in the syntheses of the nonsteroidal anti-inflammatory drugs, ketoprofen.
reactions performed in water under mild conditions of temperature and
use of environmentally compatible, biodegradable catalyst (an enzyme)
derived from renewable raw materials.
High activities and chemo - , regio - , and
stereoselectivities are obtained in reactions of multifunctional molecules without
the need for the functional group activation and
environmentally attractive and cost - effective processes ,fewer steps and less waste
EXAMPLE- Pregabalin is used to relieve neuropathic pain (pain from damaged nerves) chemoenzymatic process
enzymatic kinetic resolution of an ester using the readily available lipase from Thermomyces lanuginosus (Lipolase) with subsequent thermal decarboxylation step.
The unreacted substrate was racemized by heating with a catalytic amount of sodium
ethoxide in toluene at 80 ° C and was then recycled to the resolution step.
Subsequent hydrolysis and hydrogenation affords pregabalin in 40 – 45% overall yield.
which decreased 7 - fold, from 86 to 12
Cyclohexane- bisulfate salt of caprolactum- neutralize with NH3- E-caprolactum+NH4SO4(4.4kgkg/kg of product)
Flixborough disaster in 1974 due to benzene based cyclohexane vapor cloud explosion
So, Beckmann reaction alternative is used
Benzene istoxic and the process is highly air polluting
1. Hydrogenate benzene and use H2O2 as oxidizing agent
2. use of butadiene(benign)
3. cyclohexene and the phase-transfer catalyst, Alamine 336 [tri-(C8–C10)alkylamine
5.Decline in acetylene Chemistry
Initially: CaC2 +2H2O-> Ca(OH)2+CH-triple bond-CH
28tonnes of Ca(OH)2/ton of product
Replacement: CH=CH- steam cracking at 750-950oC
11CHE1051 Neha Bakhre
11CHE1007 Karishma Attarkar
11CHE1029 Snehal Tadge
11CHE1037 Nikita Ghode
11CHE1041 Vrushali Gardare
11CHE1048 Kinjal Valendra
11CHE1052 Tejal Kamble
11CHE1056 Ruchita Sutar
ESTIMATED POLLUTANT ABADENT COST BY INDUSTRY,2005.
3. Introduction to Green Chemistry, Organic Synthesis and Pharmaceuticals Roger Sheldon
4. industrial organic chemicals HAROLD A. WITTCOFF