Organic Solvents Overview

Alternative Organic Solvents

• Alternative organic solvents are liquid substances used in applications to dissolve other substances.
• The solvent can be recovered unchanged after removal.
• Research in green chemistry focuses on environmentally benign and economically feasible chemical processes and syntheses.
• The goal of green chemistry is to reduce hazards from products and processes.

Solvent Usage

• Solvents are crucial in various industrial and laboratory applications.
• They extensively participate in reactions, work-ups and purifications.
• Solvents are used in coatings, like paints and adhesives.
• Removal of solvents often occurs through evaporation.

Wide Applications

• Solvents are vital in synthetic and analytical chemistry.
• They act as reaction media in laboratory and industrial processes.
• Solvents are extensively used in work-up and purification stages.
• Solvents are important for sample extraction and preparation.
• They are used in chromatography techniques such as HPLC and TLC.
• Solvents are crucial for crystal purification and analysis through recrystallization techniques.

Criteria for Solvent Selection

• Evaluation of the necessity of the substance.
• Identification of less toxic alternatives.
• Assessment of risks and benefits for continued usage.
• Evaluation of environmental impact.
• Analysis of resource depletion during procurement.
• Examination of successful final disposal methods.
• Determination of safe usage technologies.

Solvents as Green Chemistry Tools

• Understanding the hazardous properties of a chemical.
• Manipulating chemical structures to mitigate hazards.

Solvents Effects and Green Chemistry

• Studying solvent effects requires employing conceptual approaches such as theories of molecular structures and the concept of polarity.
• Bulk properties encompass dielectric constants and density.

Goals of Green Chemistry

• The goal of green chemistry includes minimizing hazards involved in products and processes.
• This aims to enhance not only the quality of life but also technical achievements.
• Risk = Hazard × Exposure.

Green Solvents & Definitions

• An ideal green solvent combines safety for humans with reduced hazards and easy degradability.
• High product yield is an additional desirable characteristic.
• The solvent should have less human and environmental absorption.
• Understanding environmental toxicity and environmental fate is crucial for solvent selection.

Greener Solvent Alternatives

• Water (including supercritical water), methanol, nitromethane, ethanol, DMF, DMSO, HMPA, acetonitrile, pyridine and ammonia are some greener solvents.
• Ionic liquids, perfluorinated hydrocarbons, and supercritical fluids are also potential greener alternatives.

Water as a Reaction Medium

• Water is a cost-effective and readily available alternative to volatile organic compounds (VOCs).
• It is beneficial in certain reactions but limited by low solubility with organic substrates and issues with waste disposal.
• It is useful in biphasic processes combined with other solvents.

Water as Dual Activator Medium

• Water's hydrogen bonding capability enables it to activate both nucleophiles and electrophiles, thus accelerating polar reactions.

Carbon Dioxide

• Carbon dioxide (CO2) offers advantages resembling water, being natural, inexpensive, abundant, readily available in high purity, and a byproduct.
• Its non-toxicity and well-understood properties are valuable too.
• It is easily removed and recycled.
• CO2 facilitates solvent-free product isolation with 100% dryness.
• It has potential in diverse product processing steps like extraction, particle formation, or chromatography.

Supercritical Fluids (SCFs)

• SCFs are substances neither gaseous nor liquid, possessing properties of both.
• No sharp boundary between gas and liquid phases exists.
• Carbon dioxide (CO2) and water are examples of SCFs.

Possible Advantages of Supercritical Fluids

• Increased solubilities of reactants or products leading to homogenous phases, eliminating transport limitations.
• Recovering SCFs, such as water and CO2. has low environmental impact.
• Fine-tuned reaction conditions through pressure and temperature adjustments.
• Elimination of separation steps.
• Solubility of organic compounds in SCFs; insolubility of inorganic salts.

Advantages of ScCO2

• High compressibility allows significant solvent property adjustments with minor pressure changes.
• Tailoring solvent properties for targeted reaction pathways and increased reaction rates.
• Low molecular diffusion rates are also possible.

Extraction using ScCO2

• ScCO2 excels in decaffeinating and brewing processes.
• It is used for essential oils and fragrances extraction.
• An environmentally friendly extraction method.

Ionic Liquids (ILs)

• ILs typically comprise an organic cation (often ammonium or phosphonium salt) and an inorganic anion.
• They are typically liquid at room temperature.
• Diverse structures are possible.
• Their low vapor pressure is beneficial in comparison to volatile organic compounds (VOCs).

Ionic Liquids as Reaction Media

• ILs are promising media for various chemical reactions.
• They are capable of facilitating Diels-Alder reactions, alkylation, hydroformylation, and Friedel-Crafts reactions.
• They also contribute to Pd-mediated C-C bond formation and alkene polymerisation.
• Ionic Liquids applications in biotransformation processes.

Ethyl Lactate

• Ethyl lactate is derived from corn processing.
• It displays a variety of possible lactate esters.
• This is a renewable resource, non-petrochemical-based solvent.
• It is biodegradable, recyclable, and non-corrosive.
• It's non-carcinogenic and non-ozone depleting.
• This is a good solvent for various processes and commonly employed in the paint and coatings industry.

Specific Health & Environmental Requirement

• Specific health and environmental requirements encompass: toxic chemicals, carcinogens and reproductive toxins, flammability, ozone depletion, and aquatic life toxicity.
• Characterization of solvents based on their LD50 (lethal dose) values.

Flammability

• The solvent's flash point should be above 100°F to prevent flammability risks.

Ozone Depletion

• Solvents should not contain Class-I or Class-II ozone-depleting substances.

Toxicity to Aquatic Life

• Solvents should not harm aquatic life.

Green Solvents for Academic Chemistry

• Teaching environmental impact alongside basic chemistry is important for non-science students.
• Focusing on environmental aspects of chemistry, along with fundamental chemical processes and related points concerning efficiency and pollution.

Physical Properties of Solvents

• Solvent physical properties heavily influence applications.
• Liquid state is necessary under the specific temperature and pressure conditions.
• Identifying thermodynamic properties (density, vapor pressure, temperature, and pressure coefficients, heat capacity and surface tension).
• Understanding transport properties (viscosity, diffusion coefficient and thermal conductivity).

Chemical Properties of Solvents

• Chemical properties critically affect the suitability for various uses.
• Structure plays a key role in properties such as volatility, viscosity, diffusion coefficient and relaxation rates.
• Properties, such as stiffness and openness.
• Solvent properties like polarity are influenced by intermolecular forces and are characterized by dipole moments.

Application of Green Solvents

• Green solvents find applications in new syntheses.
• They are valuable in integrated circuit production, removing pollutants from wood, developing new pesticides, and purifying water.
• They contribute to environmentally responsible paint and coating production, and the development of recyclable carpeting materials.
• Replacing volatile organic compounds (VOCs) and chlorinated solvents.
• Biodegradable polymers are used for sustainable purposes.

Energy Efficiency

• Enhancing reaction rate(s) or improving chemical reaction completion through energy efficiency methods like lowering activation energy, using catalysts.
• Reducing energy usage by using ambient temperatures and/or pressures where possible.
• Implementing more efficient ways to use non-renewable sources of energy.

Energy Efficiency Example

• Employing microwave irradiation, sonochemistry, electrochemistry or photochemistry to expedite reactions and reduce resource consumption.

Applications area of Energy Efficiency

• Incorporating renewable energy into buildings.
• Developing more energy-efficient vehicles.
• Upgrading homes with energy-efficient products.
• Implementing energy-efficient processes in industries.
• Utilizing low-power modes for computers and laptops.

Need to Design Energy Efficiency

• Reducing the greenhouse effect by adopting energy-efficient solutions.
• Controlling energy consumption through household and economic practices.
• Reducing energy imports by fostering energy efficiency.

Conclusion

• Energy efficiency, a cost-effective method, combats climate change.
• It reduces costs for consumers and enhances business competitiveness.
• Energy efficiency is essential to decarbonization and achieving net-zero carbon emissions.
• It leads to a resilient electric grid and provides environmental, community and health benefits.