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Questions and Answers
What is one of the advantages of using microwaves in reactions?
What is one of the advantages of using microwaves in reactions?
Sonochemistry introduces energy into a reaction medium by using high-frequency ultrasound.
Sonochemistry introduces energy into a reaction medium by using high-frequency ultrasound.
True
What is the primary role of electrochemistry in reactions?
What is the primary role of electrochemistry in reactions?
To cause reductions and oxidations through the passage of direct current.
The energy of a photon of electromagnetic radiation is given by the formula E = hν, where h is _______.
The energy of a photon of electromagnetic radiation is given by the formula E = hν, where h is _______.
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Match the following methods with their primary characteristic:
Match the following methods with their primary characteristic:
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Which of the following solvents is commonly used in microwave-enhanced reactions?
Which of the following solvents is commonly used in microwave-enhanced reactions?
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Electrochemical processes add matter to the reaction medium.
Electrochemical processes add matter to the reaction medium.
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What is one benefit of electrolytic syntheses in relation to green chemistry?
What is one benefit of electrolytic syntheses in relation to green chemistry?
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What is one way to enhance chemical reactions according to the principles of green chemistry?
What is one way to enhance chemical reactions according to the principles of green chemistry?
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Microwaves can only be used in communications and cannot enhance chemical reactions.
Microwaves can only be used in communications and cannot enhance chemical reactions.
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What is the role of catalysts in chemical reactions?
What is the role of catalysts in chemical reactions?
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One of the most straightforward means to add energy to a reaction is by __________ the reaction mixture.
One of the most straightforward means to add energy to a reaction is by __________ the reaction mixture.
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Which of the following wavelengths corresponds to microwaves?
Which of the following wavelengths corresponds to microwaves?
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The only method for adding energy to a chemical system is through heating.
The only method for adding energy to a chemical system is through heating.
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What are polar molecules mentioned in the context of microwaves?
What are polar molecules mentioned in the context of microwaves?
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Match the energy addition method with its description:
Match the energy addition method with its description:
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Study Notes
Alternative Organic Solvents
- Solvents are liquid substances used to dissolve other substances during application, recovering the initial substances unchanged after removing the solvent.
- Research in green chemistry aims to design environmentally benign and economically viable chemicals, chemical syntheses, and processes.
- The goal of green chemistry is to minimize the risks associated with products and processes.
Objectives
- Solvent Usage
- Solvent effects & Green Chemistry
- Green Solvents & Definitions
- Specific Health & Environmental Requirements
- Green Solvents in Green Chemistry
- Physical & Chemical Properties of Solvents
- Application of Green Solvents
Solvent Usage
- Solvents are used in various applications including, but not limited to, synthetic chemistry, coatings, cleaning, and extraction.
- Research in green chemistry has resulted in significant achievements in chemical design, chemical syntheses, and chemical processes.
- Processes should be environmentally friendly and economically feasible.
- The objective of green chemistry involves reducing the risks associated with products and processes.
Alternative Organic Solvents
- Widely used in synthetic chemistry, analytical chemistry, and crystallisation.
- Used as a reaction medium in industrial and laboratory scale.
- Often used in work-up and purification more than reaction mediums.
Wide Usage Areas
- Synthetic Chemistry
- Reaction mediums in labs and industries
- Used for work-up and purification extensively
- Analytical Chemistry
- Sample extraction and preparation (spectroscopy)
- Chromatography mobile phase (HPLC, TLC)
- Crystallisation
- Purification to obtain crystals useful for analysis.
Application of Green Solvents
- New synthesis of ibuprofen and Zoloft
- Integrated circuit production
- Removal of arsenic and chromate from pressure treated wood
- Development of many new pesticides
- Oxidising agents used in bleaching paper and disinfecting water
- Extracting lead from car paint
- Recyclable carpeting materials
- Replacing VOCs and chlorinated solvents
- Using renewable resources
Green Solvents & Their Definitions
- The goal of green chemistry is to reduce hazards associated with products and processes, maintaining both quality of life and technical achievements
- Reduction of risk, where RISK = HAZARD × EXPOSURE
- Solvents play a major role in the environmental performance of chemical industry processes—affecting cost, safety, and health.
- The concept of "green" solvents minimizes the environmental impact of solvents in chemical production.
Green Solvents & Criteria
- Must have human safety
- Reduced hazard
- Easily degradable
- Provide high product yield
- Have less human and environmental absorption
- Understand environmental toxicity
- Understand environmental fate
Greener Solvents
- Water
- Methanol
- Nitromethane
- Acetone
- Ethanol
- DMF
- DMSO
- HMPA
- Acetonitrile
- Pyridine
- Ammonia
- Supercritical fluids
- Ionic liquids
- Perfluorinated hydrocarbons
- Lactate esters
Water as a Reaction Medium
- One of the obvious alternatives to volatile organic compounds (VOCs).
- Cheap, readily available, and plentiful in some regions.
- Useful for certain reactions, but limited due to low solubility of organic substrates and incompatibility with certain reagents.
- Aqueous waste cleanup can be difficult.
- Useful in biphasic processes with other solvents.
- Can be a dual activator, activating nucleophiles and electrophiles simultaneously and accelerating their reactions.
Carbon Dioxide
- Similar advantages as water
- Natural, cheap, abundant, and available in high purity.
- By-product in many industrial processes.
- Non-toxic, and its properties are well understood.
- Easy to remove and recycle, leading to no net increase in global CO2.
- Simple product isolation by evaporation, achieving 100% dryness.
- No solvent residue or effluent created.
- Potential applications in extraction, particle formation, and chromatography.
Supercritical Fluids (SCFs)
- A pure fluid above its critical temperature and pressure (Tc and Pc) is a supercritical.
- No sharp boundaries between gas and liquid phases.
- Properties that vary significantly from typical fluid phases.
- Advantages include increased reactant or product solubility, single homogeneous phases, easily recovered or disposed of with minimal environmental impact.
- Reaction parameters like pressure and temperature are readily adjustable.
- Separation steps can be bypassed, and numerous uses, including organic compound recovery and inorganic salt insolubility, exist
Advantages of ScCO2
- High compressibility
- Large property changes with small pressure variations
- Ability to fine-tune reaction pathways based on temperature or pressure
- High diffusion rates leading to faster reactions
- Homogeneous catalytic processes, with multiple catalysts and substrates in one phase
- Inert to oxidation and reduction
- Ideal for oxidation and reduction reactions
Extraction using ScCO2
- Extraction of coffee, tea, hops, spices, essential oils and fragrances.
- Simple product isolation via evaporation to 100% dryness.
- No solvent residues or effluent generated.
Ionic Liquids (ILs)
- Typically consist of an organic cation (often ammonium or phosphonium) and an inorganic anion.
- Exist as liquids at room temperature.
- Wide range of possible structures.
- Very low vapor pressure.
- Less volatile than VOCs.
Ionic Liquids as Reaction Media
- Applications in various reactions, including Diels-Alder, alkylation, hydroformylation.
- Useful applications in Friedel-Crafts reactions, palladium-mediated C-C bond formation, alkene polymerisation, and biotransformations.
Ethyl Lactate
- Derived from processed corn starch.
- Variety of similar lactate esters possible.
- Renewable source (non-petrochemical).
- Attractive solvent properties (biodegradable, easy to recycle, non-toxic, non-corrosive, and non-ozone depleting.
- Commonly utilized in the paint and coating industry and potentially suitable for many further applications.
Specific Health & Environmental Requirements
- Includes consideration of toxic chemicals (including carcinogens and reproductive toxins), flammability and ozone depletion.
- Includes toxicity to aquatic life.
- Solvents must have an oral LD50 above 50 mg/kg and a dermal LD50 above 200 mg/kg.
Flammability
- The solvent should not be flammable.
- The flash point of the chemical should be above 100°F
Ozone Depletion
- The solvent should not contain any class I or class II ozone-depleting substances.
Toxicity to Aquatic Life
- Chemicals used should not have any effect on aquatic life
Green Solvents for Academic Chemistry
- Include both environmental concerns and basic chemistry.
- Employ environmental points for basic chemistry.
- Ensure chemical processes are shown, replacing environmentally harmful alternatives with less harmful ones.
- Set goals for green research and provide green technologies to replace existing harmful ones.
- Create awareness about different hazardous chemicals in schools and colleges.
- Provide information to employees through material safety data sheets (MSDS).
Physical Properties of Solvents
- Physical properties greatly affect solvents' choice.
- Liquid state under the temperature and pressure conditions in use.
- Thermodynamic properties such as density, vapor pressure, the temperature/pressure coefficients, heat capacity, and surface tension are important.
- Transport properties like viscosity, diffusion coefficients, and thermal conductivity must also be considered.
Chemical Properties of Solvents
- Chemical properties significantly influence applications.
- Solvents' properties such as volatility, viscosity, diffusion coefficient, and relaxation rates are important quantitative metrics related to their structural aspects.
- Stiffness is represented by cohesive energy density.
- Openness is the gap between a solvent's molar volume and its intrinsic volumes.
- Ordering describes the solvent vapor entropy deficit compared to its liquid state or the dipole orientation correlation.
Polarity in Molecules
- Dispersion forces influence molecules with no initial dipole, with electron movement.
- Polarization/polarizability is significant if dipoles exist without applied electric fields, with random dipole orientation.
- Dipole-dipole interactions between rotating dipoles are minor in most cases, while they become prominent if hydrogen bonding is absent and large dipole moments are present.
Dipole Moments
- A comparison of selected solvent dipole moments (values provided for specific solvents).
Application of Green Solvents
- New synthesis of ibuprofen and Zoloft
- Integrated circuit production
- Removing arsenic and chromate from pressure-treated wood
- Development of many new pesticides
- Oxidising agents used in bleaching paper and disinfecting water
- Extracting lead from car paint
- Recyclable carpeting materials
- Replacing VOCs and chlorinated solvents
- Using renewable resources
Energy Efficiency
- Introduction
- Design for energy efficiency
- Need to design energy efficiency
- Example of energy efficiency
- Application area of energy efficiency
Electrochemistry
- The addition of electrons via a direct current causes oxidation-reduction reactions.
- Reduction occurs at the negatively charged cathode.
- Oxidation occurs at the positively charged anode.
- Electrochemical oxidation-reduction reactions are controlled based on potential, medium, and electrochemical cell.
- Electrolytic syntheses meet green chemistry goals as the introduction/removal of electrons doesn't affect chemical mass.
Photochemistry
- Light/UV radiation energies cause reactions (E=hv).
- Molecules or functional groups absorb photons directly.
- Reactions occur with less waste compared to typical reactions, often without heating significantly.
- An example of this is the acylation of benzoquinone with aldehydes, forming acyl hydroquinone as an intermediary useful in producing various specialty polymers.
Applications
- Buildings
- Vehicles
- Homes
- Industries
- Computers and laptops use lower power modes.
Conclusion
- Energy efficiency is crucial for addressing climate change, lowering consumer costs, boosting business competitiveness, and minimizing carbon dioxide emissions in decarbonization.
- Improved resilience and reliability of the electric grid, along with community/environmental/health benefits are additional advantages of energy efficiency strategies.
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Description
Test your knowledge on the applications of microwaves and electrochemistry in chemical reactions. This quiz covers the principles of sonochemistry, the role of catalysts, and the benefits of green chemistry. Assess your understanding of how various methods and energies enhance chemical processes.
