绿色化学电子教案
绿色化学电子教案
Chapter 2
Green Chemistry
Chapter 2
Green Chemistry
绿色化学电子教案
绿色化学电子教案
GREEN CHEMISTRY
DEFINITION
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 .
绿色化学电子教案
绿色化学电子教案
GREEN CHEMISTRY IS ABOUT
• Waste Minimisation at Source
• Use of Catalysts in place of Reagents
• Using Non-Toxic Reagents
• Use of Renewable Resources
• Improved Atom Efficiency
• Use of Solvent Free or Recyclable Environmentally
Benign Solvent systems
绿色化学电子教案
绿色化学电子教案
Green Chemistry Is About...
Cost
Waste
Materials
Hazard
Risk
Energy
绿色化学电子教案
绿色化学电子教案
Chemistry is undeniably a very prominent part of our daily
lives.
Chemical developments also bring new environmental
problems and harmful unexpected side effects, which
result in the need for ‘greener’ chemical products.
Why do we need Green Chemistry ?
A famous example is the pesticide
DDT.
绿色化学电子教案
绿色化学电子教案
Green chemistry looks at pollution prevention on the molecular
scale and is an extremely important area of Chemistry due
to the importance of Chemistry in our world today and the
implications it can show on our environment. The Green
Chemistry program supports the invention of more
environmentally friendly chemical processes which reduce
or even eliminate the generation of hazardous substances.
绿色化学电子教案
绿色化学电子教案
Transportation - production of gasoline and diesel from
petroleum, fuel additives for greater efficiency and reduced
emissions, catalytic converters, plastics to reduce vehicle
weight and improve energy efficiency.
Clothing - man-made fibres such as rayon and nylon, dyes,
water proofing and other surface finishing chemicals.
Sport - advanced composite materials for tennis and squash
rackets, all-weather surfaces.
绿色化学电子教案
绿色化学电子教案
Safety - lightweight polycarbonate cycle helmets, fire-retardant
furniture.
Food - refrigerants, packaging, containers and wraps, food processing
aids, preservatives.
Medical - artificial joints, ‘blood bags’, anaesthetics, disinfectants, anti-
cancer drugs, vaccines, dental fillings, contact lenses, contraceptives.
Office - photocopying toner, inks, printed circuit boards, liquidcrystal
displays.
Home - material and dyes for carpets, plastics for TVs and
mobilephones, CDs, video and audio tapes, paints, detergents.
Farming - fertilizers, pesticides.
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绿色化学电子教案
Atom economy is a measure of how many atoms of reactants
end up in the final product and how many end up in
byproducts or waste. The real benefit of atom economy is
that it can be calculated at the reaction planning stage from
a balanced reaction equation. Taking the following
theoretical reaction:
X + Y = P + U
the reaction between X and Y to give product P may proceed
in 100% yield with 100% selectivity but because the
reaction also produces unwanted materials U its atom
economy will be less than 100%.
ATOM ECONOMY
绿色化学电子教案
绿色化学电子教案
绿色化学电子教案
绿色化学电子教案
ATOM ECONOMIC REACTIONS
Rearrangement Reactions
Rearrangements, especially those only involving heat or a
small amount of catalyst to activate the reaction, display
total atom economy. A classic example of this is the Claisen
rearrangement, which involves the rearrangement of
aromatic ally1 ethers.
绿色化学电子教案
绿色化学电子教案
Substitutions are very common synthetic reactions; by
their very nature they produce at least two products, one of
which is commonly not wanted. As a simple example 2-
chloro-2-methylpropane can be prepared in high yield by
simply mixing 2-methylpropan-2-o1 with concentrated
hydrochloric acid (Scheme 1.10). Here the hydroxyl group
on the alcohol is substituted by a chloride group in a facile
SNl reaction. Whilst the byproduct in this particular
reaction is only water it does reduce the atom economy to
83%.
ATOM UN-ECONOMIC REACTIONS
Substitution Reactions
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绿色化学电子教案
Elimination reactions involve loss of two substituents from
adjacent atoms; as a result unsaturation is introduced. In
many instances additional reagents are required to cause the
elimination to occur, reducing the overall atom economy
still further. A simple example of this is the E2 elimination
of HBr from 2-bromopropane using potassium t-butoxide
(Scheme 1.12). In this case unwanted potassium bromide
and t-butanol are also produced reducing the atom economy
to a low 17%.
Elimination Reactions
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绿色化学电子教案
Wittig reactions are versatile and useful for preparing
alkenes, under mild conditions, where the position of the
double bond is known unambiguously. The reaction
involves the facile formation of a phosphonium salt from
an alkyl halide and a phosphine. In the presence of base
this loses HX to form an ylide (Scheme 1.15). This highly
polar ylide reacts with a carbonyl compound to give an
alkene and a stoichiometric amount of a phosphine oxide,
usually triphenylphosphine oxide.
Wittig Reactions
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绿色化学电子教案
REDUCING TOXICITY
One of the underpinning principles of green chemistry is to
design chemical products and processes that use and
produce less-hazardous materials. Here hazardous covers
several aspects including toxicity, flammability, explosion
potential and environmental persistence.
A hazard can be defined as a situation which may lead to
harm, whilst risk is the probability that harm will occur.
From the point of view of harm being caused by exposure
to a chemical,
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绿色化学电子教案
Many methods have now been developed for measuring the
potential harmful effects chemicals can have. Common tests
include those for irritancy, mutagenic effects, reproductive
effects and acute toxicity.
Measuring Toxicity
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绿色化学电子教案
“It is better to prevent waste than to treat or clean up waste after it is formed”
Chemical
Process
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绿色化学电子教案
“The use of auxiliary substances (e.g. solvents, separation
agents, etc.) should be made unnecessary wherever possible,
and innocuous when used”
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绿色化学电子教案
HeatingCoolingStirringDistillationCompressionPumping Separation
Energy Requirement(electricity)
Burn fossil fuel
CO2 toatmosphere
GLOBAL WARMING
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绿色化学电子教案
“A raw material of feedstock should be renewable rather than depleting wherever technically and economically practical”
Non-renewable Renewable
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绿色化学电子教案
绿色化学电子教案
绿色化学电子教案
Poly lactic acid (PLA) for plastics production
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绿色化学电子教案
Polyhydroxyalkanoates (PHA’s)
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绿色化学电子教案
Energy
Global Change
Resource Depletion
Food Supply
Toxics in the Environment
The major uses of GREEN CHEMISTRY
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绿色化学电子教案
Energy
The vast majority of the energy generated in the world today
is from non-renewable sources that damage the
environment.
Carbon dioxide
Depletion of Ozone layer
Effects of mining, drilling, etc
Toxics
绿色化学电子教案
绿色化学电子教案
Energy
Green Chemistry will be essential in
developing the alternatives for energy generation
(photovoltaics, hydrogen, fuel cells, biobased fuels,
etc.) as well as
continue the path toward energy efficiency with
catalysis and product design at the forefront.
绿色化学电子教案
绿色化学电子教案
Global Change
Concerns for climate change, oceanic temperature,
stratospheric chemistry and global distillation can be
addressed through the development and
implementation of green chemistry technologies.
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绿色化学电子教案
Resource Depletion
Due to the over utilization of non-renewable resources, natural resources are being depleted at an unsustainable rate.
Fossil fuels are a central issue.
绿色化学电子教案
绿色化学电子教案
Resource Depletion
Renewable resources can be made increasingly viable
technologically and economically through green chemistry.
Biomass
Nanoscience & technology
Solar
Carbon dioxide
Chitin
Waste utilization
绿色化学电子教案
绿色化学电子教案
Food Supply
While current food levels are sufficient, distribution is
inadequate
Agricultural methods are unsustainable
Future food production intensity is needed.
Green chemistry can address many food supply issues
绿色化学电子教案
绿色化学电子教案
Food Supply
Green chemistry is developing:
Pesticides which only affect target organisms and
degrade to innocuous by-products.
Fertilizers and fertilizer adjuvants that are designed to
minimize usage while maximizing effectiveness.
Methods of using agricultural wastes for beneficial
and profitable uses.
绿色化学电子教案
绿色化学电子教案
Toxics in the Environment
Substances that are toxic to humans, the biosphere and all
that sustains it, are currently still being released at a
cost of life, health and sustainability.
One of green chemistry’s greatest strengths is the ability
to design for reduced hazard.
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绿色化学电子教案
Prevention & Reduction
Recycling & Reuse
Treatment
Disposal
Pollution Prevention Hierarchy
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绿色化学电子教案
The 12 Principles 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 maximize 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.
绿色化学电子教案
绿色化学电子教案
4. Designing Safer Chemicals
Chemical products should be designed to effect their desired function while
minimizing their toxicity.
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 minimized. If possible,
synthetic methods should be conducted at ambient temperature and pressure.
绿色化学电子教案
绿色化学电子教案
7. Use of Renewable Feedstocks
A raw material or feedstock should be renewable rather than depleting whenever
technically and economically practicable.
8. Reduce Derivatives
Unnecessary derivatization (use of blocking groups, protectiodde-protection, and
temporary modification of physicalkhemical processes) should be minimized
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 stoichiometricreagents.
绿色化学电子教案
绿色化学电子教案
10. Design for Degradation
Chemical products should be designed so that at the end of their function theybreak 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 minimize the potential for chemical accidents, including releases, explosions, and fires.