Green Chemistry - 1A03 (Term 1)

Sustainabilty

Sustainability is about "meeting the needs of the present without compromising the ability

of future generations to meet their own needs."

Case Study: Ibuprofen

Major ingredient in Advil and Motrin.

• Developed in 1960 as a potentially safer

alternative to Aspirin.

• NSAID (non-steroidal anti-inflammatory)

headaches, analgesic (pain relief), fever

relief, inflammatory diseases,

rheumatoid disorders, etc.

• Inhibits enzyme that produces

prostaglandins (chemicals that trigger

pain and inflammation).

Green Chemsitry

Green Chemistry is a revolutionary

approach to the way that products are

made; it is a science that aims to reduce

or eliminate the use and/or generation of

hazardous substances in the design

phase of materials development.

How can green chemistry be implemented?

1) Improve resource use

2) Increased energy efficiency

3) Reduced human health and enviornmental hazards

Improved Resource Use

• We want materials to come from renweal feedstocks

• If we can get our starting material from bacteria, fungi, algae, it will be much more efficient

Increased Energy Efficiency

• Run processes at low temperatures and pressures

Reduced human health and environmental hazards

Protect workers at the chemical plant and consumers who use the products.

Use non-toxic or less toxic chemicals.

Make chemicals biodegradable so they break down into simpler substances (e.g., CO₂ and H₂O).

Example: DDT was used to repel/control mosquitoes but had harmful effects on the environment.

3 main factors for Reduced human health and environmental hazards

3 main factors:

1. Limit accidents during manufacturing.

2. Limit accidents during use.

3. Reduce hazards during disposal.

The Twelve Principles of Green Chemistry

1) Waste prevention

2) Atom Economy

3) Less hazardous chemical synthesis

4) Designing safer chemicals

5)Safer solvents

6) Design for energy efficiency

7) Use of renewable feedstocks

8) Reduce derivatives

9) Catalysis

10) Design for degradation

11) real time analysis for pollution prevention

12) Inherently safer chemistry for accident prevention

Catalyst

Speeds up the rate of a chemical requestion. Reaches equilibrium faster and is not consumed in a reaction.

Solvent

Substances are dissolved in a solvents, which are usually liquids to form solutions.

• Solute is the minority, solvent is the majority.

Green Chemistry Benefits

• Energy optimization:

reduced temperature

• Many are reusable

• Direct synthesis routes,

reduced intermediate

products and waste

• Faster reaction time

What are solvents used for?

• Dissolving solutes

• Making solutions with a certain concentration

• Efficiently mixing a reaction

• Controlling the amount of energy (heating or cooling)

• Isolating and purifying a product from the unwanted byproducts

• water is the safest solvent and has a high heat cpacity

• others come with additional hazards

• in green chemistry you use safer solvents

• having no solvents is also better because it now has to be treated wich energy time and money.

How can we telll if something is '“green”

• To evaluate whether a process is

“green” requires metrics or calculations

to quantify how efficient it is, how much

waste is produced, how hazardous it is,

how renewable it is, etc.

• We typically compare two processes to

each other to determine which one is

greener

• “Green” is not a Binary – there are

“shades of green!”

• Green is a spectrum

• We use green to compare the process of things

Implications of Old synthesis of ibuprofen:

More reaction steps - 6

More chemical waste and pollution

Lower atom economy

Higher manufacturing costs

New synthesis of ibuprofen:

Fewer reaction steps - 3

Less chemical waste and pollution

Better atom economy

Lower manufacturing costs

Less environmental harm

Green chemistry Metrics

metrics are used to quantify the efficiency or environmental performance of a chemical process.

Three green chemistry metrics

1) Atom Economy

2) Reaction Mass Efficiency

3) E factor

These metrics target Waste prevention, and atom economy

Green chemistry metrics

• To evaluate whether a process is

“green” requires metrics or calculations

to quantify how efficient it is, how much

waste is produced, how hazardous it is,

how renewable it is, etc.

• We typically compare two processes to

each other to determine which one is

greener

• “Green” is not a Binary – there are

“shades of green!”

Old synthesis of ibuprofen:

• More reaction steps

• More chemical waste and pollution

• Lower atom economy

• Higher manufacturing costs

• Higher e factor produces more waste

• Lower RME because more reactant mass is wasted.

New synthesis of ibuprofen:

• Fewer reaction steps

• Less chemical waste and pollution

• Better atom economy

• Lower manufacturing costs

• Less environmental harm

• Lower e factor, produces less waste

• Higher RME because more reactant mass becomes the desired product.

Atom Economy

Atom Economy: ratio of the molar mass of the desired product to the total molar mass

of all reactants

Goal: all atoms from the reactant materials should be incorporated into the final

(desired) product.

• If atom economy is high, Most of the matter started out in the reactant goes into the desired product, which is good

Reaction Mass Efficiency

RME: A measure of how materially efficiently the mass of reactants is converted into the

desired product, considering both atom economy and reaction yield.

Goal: all atoms from the reactant materials should be incorporated into the final

(desired) product, with the best possible yield. (Note: there are different definitions of

RME)

• If percent yield is anything other than 100%, the RME is always going to be lower than the atom economy

• A lower reaction yield in a synthesis means more waste, and more energy to separate products from unwanted side reactions.

E - factor

E factor: ratio of the total mass of waste to the mass of the desired product.

Goal: reduce waste, including excess reactants, solvents, byproducts.

• the larger the e-factor, the less sustainable the process is going to be

E-Factor values

Summary of green chemistry

Which is greener?

Life cycle assesment

LCA evaluates the environmental impact of a product, process, or service,
including all inputs and outputs, across its entire life cycle.

Summary of green chemistry and LCA

UN Sustainable Development Goals

• UN SDGs are an example of

systems thinking

• 17 goals to achieve world

peace and prosperity

• Found in the 2030 Agenda for

Sustainable Development

• 2015: adopted by all UN

member states (incl. Canada)

• Each goal has targets and

indicators used to monitor

progres

17 UN SDGS