GREEN CHEMISTRYDr. MARY JELASTIN KALA,

GREEN CHEMISTRYDr. MARY JELASTIN KALA,ASSISTANT PROFFESOR,ST. XAVIERS AUTONOMOUS COLLEGE.COLLEGE.

TOPICTOPIC

1. Introduction

2. Need for Green Chemistry2. Need for Green Chemistry

3. 12 Principles of Green Chemistry

4. Atom Economy4. Atom Economy

5. Solvents

1. SCO

2. Ionic liquids2. Ionic liquids

3. Water

INTRODUCTION INTRODUCTION

NEED FOR GREEN CHEMISTRY NEED FOR GREEN CHEMISTRY

• There is increasing pressure from both society and governments for chemistry-• There is increasing pressure from both society and governments for chemistry-based industries to become more sustainable through development of eco-friendly products and processes that both reduce waste and prevent toxic substances from entering the environment.substances from entering the environment.

• The chemical industry is vitally important to the world economy; however the success of the industry has led to some environmental damage and a low public perception of the industry. In order to prevent further environmental damage and perception of the industry. In order to prevent further environmental damage and to encourage more young people into the industry, the public acceptability needs to be raised by adoption of greener and cleaner processes and green product design.design.

• Industry is making progress, but it is frequently commented that new graduates are not • Industry is making progress, but it is frequently commented that new graduates are not adequately equipped with the tools, techniques, and culture to ensure that they can rapidly make a positive impact on industry's increasing requirement for green chemistry and sustainable technology.sustainable technology.

• Globally there is a growing requirement for cleaner processes and products, with many 'third-world' countries now insisting that licensed technology is the cleanest available while the EU is leading the world in its requirements for greener products. In order to ensure the the EU is leading the world in its requirements for greener products. In order to ensure the future success of chemistry-based industries, it is vital to equip students with the requisite tools, knowledge and experience.

• The Green Chemistry Centre of Excellence (GCCE) aspires to maintain and enhance the high quality of provision of green and sustainable chemistry to enable a strategic step change to a low carbon, bio-based economy, based on core values of high quality pure and change to a low carbon, bio-based economy, based on core values of high quality pure and translational research, education, training, networking and partnerships embedded within a framework of sustainable development.framework of sustainable development.

12 PRINCIPLES OF GREEN 12 PRINCIPLES OF GREEN CHEMISTRY CHEMISTRY

ATOM ECONOMY ATOM ECONOMY

Atom economy (atom efficiency) is the conversion efficiency of a chemical process in terms of chemical process in terms of all atoms involved and the desired products produced. Atom economy products produced. Atom economy is an important concept of greenchemistryphilosophy,[1][2][3] and one of the most widely used metrics for of the most widely used metrics for measuring the "greenness" of a process or synthesis.process or synthesis.

Atom economy can be written as:atom economy =(molecular weight of desired product/ molecular weight of total

reactants) x 100%

For a Multi step process, where the intermediates are formed in one step and consumed during For a Multi step process, where the intermediates are formed in one step and consumed during a later step

1.Numbered list item A + B --> C1.Numbered list item A + B --> C2.Numbered list item C + D --> E

3.Numbered list item E + F --> G3.Numbered list item E + F --> G% Atom Economy = Mol Weight (G)/ (Mol Wt (A + B+ D + F)

• Atom economy is a different concern than chemical yield, because a high-yielding process can still result in • Atom economy is a different concern than chemical yield, because a high-yielding process can still result in substantial byproducts. Examples include the Cannizzaro reaction, in which approximately 50% of the reactant aldehyde becomes the other oxidation state of the target; the Wittig reaction, which uses high-mass phosphorus reagents that ultimately become waste; and the Gabriel synthesis, which produces a stoichiometric quantity of phthalic acid

• If the desired product has an enantiomerthe reaction needs to be sufficiently stereoselective even when atom economy is 100%. A Diels-Alder reaction is an example of a potentially very atom efficient reaction that also economy is 100%. A Diels-Alder reaction is an example of a potentially very atom efficient reaction that also can be chemo-, regio-, diastereo- and enantioselective. Catalytic hydrogenation comes the closest to being an ideal reaction that is extensively practiced both industrially and academically.[4]

• Atom economy can also be adjusted if a pendant group is recoverable, for example Evans auxiliary groups. However, if this can be avoided it is more desirable, as recovery processes will never be 100%. Atom economy can be improved upon by careful selection of starting materials and a catalystsystem.economy can be improved upon by careful selection of starting materials and a catalystsystem.

• Poor atom economy is common in fine chemicals or pharmaceuticals synthesis, and • Poor atom economy is common in fine chemicals or pharmaceuticals synthesis, and especially in research, where the aim to readily and reliably produce a wide range of complex compounds leads to the use of versatile and dependable, but poorly atom-economical reactions. For example, synthesis of an alcohol is readily accomplished by economical reactions. For example, synthesis of an alcohol is readily accomplished by reduction of an ester with lithium aluminium hydride, but the reaction necessarily produces a voluminous floc of aluminum salts, which have to be separated from the product alcohol and disposed of. The cost of such hazardous material disposal can be product alcohol and disposed of. The cost of such hazardous material disposal can be considerable. Catalytic hydrogenolysis of an ester is the analogous reaction with a high atom economy, but it requires catalyst optimization, is a much slower reaction and is not atom economy, but it requires catalyst optimization, is a much slower reaction and is not applicable universally.

SELECTION OF APPROPRIATE SOLVENTS -SCOSELECTION OF APPROPRIATE SOLVENTS -SCO

Supercritical carbon dioxide (sCO2) is a fluid state of carbon dioxide where it is held at or above its critical 2held at or above its critical temperature and critical pressure.

Carbon dioxide usually behaves as a gas in air at standard temperature and a gas in air at standard temperature and pressure(STP), or as a solid called dry ice when frozen. If the temperature and pressure are both increased from STP to be at or above the criticalpoint for carbon dioxide, it can adopt properties point for carbon dioxide, it can adopt properties midway between a gas and a liquid. More specifically, it behaves as a supercritical fluid above its critical temperature (304.25 K, 31.10 °C, 87.98 °F) and critical pressure (72.9 atm, 7.39 MPa, 1,071 psi, 73.9 bar), 31.10 °C, 87.98 °F) and critical pressure (72.9 atm, 7.39 MPa, 1,071 psi, 73.9 bar), expanding to fill its container like a gas but with a density like that of a liquid.

Supercritical CO2 is becoming an important commercial and industrial solvent due to its role in chemical extraction in addition to its low toxicity and environmental impact. in chemical extraction in addition to its low toxicity and environmental impact. The relatively low temperature of the process and the stability of CO2 also allows most compounds to be extracted with little damage 2 also allows most compounds to be extracted with little damage or denaturing. In addition, the solubility of many extracted compounds in CO2 varies with pressure,[1] permitting selective extractions.

IONIC LIQUIDSIONIC LIQUIDS

An ionic liquid (IL) is a salt in the liquid state. In some contexts, the term has been restricted to salts whose melting point is below some arbitrary temperature, such as 100 °C point is below some arbitrary temperature, such as 100 °C (212 °F). While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ionic liquids are largely made of ions and short-lived ion pairs. These substances are variously called liquid electrolytes, ionic melts, ionic fluids, fused called liquid electrolytes, ionic melts, ionic fluids, fused salts, liquid salts, or ionic glasses. [1][2][3] They are known as "solvents of the future" as well as "designer solvents".[citation needed]

Ionic liquids are described as having many potential Ionic liquids are described as having many potential applications. They are powerful solvents and electrically conducting fluids (electrolytes). Salts that are liquid at near-ambient temperature are important for electric battery applications, and have been considered battery applications, and have been considered as sealants due to their very low vapor pressure.

Any salt that melts without decomposing or vaporizing usually yields an ionic liquid. Sodium chloride (NaCl), for example, melts at 801 °C (1,474 °F) into a liquid that consists largely of sodium cations (Na+

) and chloride anions (Cl−) and chloride anions (Cl−). Conversely, when an ionic liquid is cooled, it often forms an ionic solid—which may be either crystalline or glassy.

The ionic bond is usually stronger than the Van der Waals forces between the molecules of ordinary liquids. For that reason, common salts tend to melt at higher temperatures than other solid molecules. Some salts are liquid at or below room temperature. Examples include compounds to melt at higher temperatures than other solid molecules. Some salts are liquid at or below room temperature. Examples include compounds based on the 1-Ethyl-3-methylimidazolium (EMIM) cation and include: EMIM:Cl, EMIM dicyanamide, (C2H5)(CH3)C3H3H3N+

2·N(CN)−

2, that melts at −21 °C (−6 °F);[4] and 1-butyl-3,5-dimethylpyridinium bromide which becomes a glass below −24 °C (−11 °F).[5]

Low-temperature ionic liquids can be compared to ionic solutions, liquids that contain both ions and neutral molecules, and in particular to the so-Low-temperature ionic liquids can be compared to ionic solutions, liquids that contain both ions and neutral molecules, and in particular to the so-called deep eutectic solvents, mixtures of ionic and non-ionic solid substances which have much lower melting points than the pure compounds. Certain mixtures of nitrate salts can have melting points below 100 °C.[6]

The term "ionic liquid" in the general sense was used as early as 1943.[7]The term "ionic liquid" in the general sense was used as early as 1943.

WATERWATER

Water is the most environmentally friendly solvent to be considered for green separation processes. Thanks to its good and tunable physicochemical properties, its use for processes. Thanks to its good and tunable physicochemical properties, its use for separation, and especially for extraction and chromatography, has been remarkably expanded. Although water has been most frequently used mixed with organic solvents in numerous applications carried out by many separation techniques at ambient or slightly numerous applications carried out by many separation techniques at ambient or slightly elevated temperatures, the main goal of this chapter is to describe its exploitation alone in extractions and chromatographic separations at high temperatures. Material and method development together with the most recent applications are presented. Extraction development together with the most recent applications are presented. Extraction applications using high-temperature water are mainly focused on studies related to biorefineries, bioactive compounds, energy technology, amino acids, and essential oils. biorefineries, bioactive compounds, energy technology, amino acids, and essential oils. Liquid chromatography with water at high temperature has been most commonly applied to analysis of pharmaceuticals, cosmetics, and food.

GREEN CHEMISTRYDr. MARY JELASTIN KALA,ASSISTANT PROFFESOR,GREEN CHEMISTRY ASSISTANT PROFFESOR,ST. XAVIERS AUTONOMOUS COLLEGE.COLLEGE.

TOPICTOPIC

1. Source of Energy

2. Microwave2. Microwave

3. Microwave – reaction

4. Hofmann elimination4. Hofmann elimination

5. Esterification

6. Sponification

SOURCE OF ENERGY – MICROWAVE SOURCE OF ENERGY – MICROWAVE

• Microwaves are a form of electromagnetic radiation with wavelengths ranging from about • Microwaves are a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter; with frequencies between 300 MHz (1 m) and 300 GHz (1 mm).[1][2][3][4][5] Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave) bands. A more above broad definition includes both UHF and EHF (millimeter wave) bands. A more common definition in radio engineering is the range between 1 and 100 GHz (wavelengths between 0.3 m and 3 mm).[2] In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.

• The prefix micro- in microwave is not meant to suggest a wavelength in the micrometerrange. Rather, it indicates that microwaves are "small" (having shorter wavelengths), compared to the radio waves used prior to microwave technology. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-microwave technology. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radiowaves are fairly arbitrary and are used variously between different fields of study.

• Microwaves travel by line-of-sight; unlike lower frequency radio waves they do not diffract around hills, follow • Microwaves travel by line-of-sight; unlike lower frequency radio waves they do not diffract around hills, follow the earth's surface as ground waves, or reflect from the ionosphere, so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). At the high end of the band they are absorbed by gases in the atmosphere, limiting practical communication distances to around a kilometer. Microwaves are by gases in the atmosphere, limiting practical communication distances to around a kilometer. Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relaynetworks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial heating, collision avoidance systems, garage door openersand keyless entry systems, and for cooking food in microwave ovens.

MICROWAVE ASSISTED REACTION MICROWAVE ASSISTED REACTION

IN WATER – HOFMANN ELIMINATION IN WATER – HOFMANN ELIMINATION

Hofmann elimination, also known as exhaustive methylation, is a process where a quaternary ammonium reacts to create a Tertiary amine and an alkene by a quaternary ammonium reacts to create a Tertiary amine and an alkene by treatment with excess methyl iodide followed by treatment with silver oxide, water, andand

• After the first step, a quaternary ammonium iodide salt is created. After replacement of iodine by • After the first step, a quaternary ammonium iodide salt is created. After replacement of iodine by an hydroxyl anion, an elimination reaction takes place to form the alkene.

• With asymmetrical amines, the major alkene product is the least substituted and generally the least stable, an observation known as the Hofmann rule. This is in direct contrast to normal least stable, an observation known as the Hofmann rule. This is in direct contrast to normal elimination reactions where the more substituted, stable product is dominant (Zaitsev's rule).

IN ORGANIC SOLVENTS - ESTERIFICATIONIN ORGANIC SOLVENTS - ESTERIFICATION

Fifty different hydrolases were screened for retention of high esterification activity in an organic solvent with citronellol as substrate. organic solvent with citronellol as substrate. Although 22 hydrolases were very active as catalysts in the organic solvent, lipase from catalysts in the organic solvent, lipase from Candida cylindracea (lipase OF 360) was selected for further examination of the effects of reaction conditions on enzyme effects of reaction conditions on enzyme activity, with regard to catalyst availability and activity retention after immobilization. and activity retention after immobilization. When the enzyme was entrapped in hydrophobic polyurethane gels, water-saturated isooctane was found to be the saturated isooctane was found to be the most suitable solvent, whereas polar solvents caused reversible catalyst

SOLVENT FREE REACTION SOLVENT FREE REACTION - SAPONIFICATION- SAPONIFICATION