Green Chemistry

Green Chemistry is a branch of chemistry that takes into consideration the design of synthetic reactions to minimise the generation of hazardous by-products, their impact on humans and the environment. Often reactions are designed to take place at low temperatures with short reaction times and increased yields. This is preferred as fewer materials are used and it is more energy efficient.

When designing routes it is important to consider ‘How green is the process?’ in this way we are shifting focus to a more sustainable future where we are emitting fewer pollutants, using renewable feedstocks and energy sources with minimal waste.

In 1998 Paul Anastas and John Warner devised the twelve principles of Green Chemistry. They serve as a framework for scientists to design innovative scientific solutions to existing and new synthetic routes. Scientists are looking into environmentally friendly reaction schemes which can simplify production as well as being able to use greener resources.

It is impossible to fulfil all twelve principles at the same time but making attempts to apply as many principles as possible when designing a protocol is just as good. The twelve principles are:

1. Prevention: waste should be prevented rather than treating waste after it has been created.

2. Atom Economy: designing processes where you are maximising the incorporation of all materials so all reagents are in the final product.

   
   

3. Less Hazardous Chemical Synthesis: synthetic methods should be designed to be safe and the hazards of all the substances should be reviewed.

4. Designing Safer Chemicals: designed to eliminate chemicals which are carcinogenic, neurotoxic, etc. essentially safe to the Earth.

5. Safer Solvents and Auxiliaries: using auxiliary substances and minimising usage of solvents to reduce waste created.

6. Design for Energy Efficiency: designing synthetic methods where reactions can be conducted at ambient temperature and pressure.

7. Use of Renewable Feedstock: raw materials used for reactions should be renewable rather than depleting.

8. Reduce Derivatives: reducing the steps required in a reaction by using catalysts/ enzymes and adding protecting or deprotecting groups or temporary modification of functionality. Extra steps require more reagents and generate a lot of waste.

9. Catalysis: catalysts lower energy consumption and increase reaction rates. They allow for decreased use of harmful and toxic chemicals.

10. Design for Degradation: chemical products should be designed so that they can break down and have no harmful effects on the environment.

11. Real-time analysis for Pollution Prevention: analytical techniques required to allow monitoring of the formation of hazardous substances.

12. Inherently Safer Chemistry for Accident Prevention: involves using safer chemical alternatives to prevent the occurrence of an accident e.g. fires; explosions.

Some examples of areas where Green Chemistry is implemented:

1. Computer Chips: the use of supercritical carbon dioxide as a step for the preparation of a chip. This has reduced the quantities of chemicals, water and energy required to produce chips.

2. Medicine: developing more efficient ways of synthesising pharmaceuticals e.g. chemotherapy drug Taxol.

Green Chemistry is widely being implemented in academic labs as a way to reduce the environmental impact and high costs. As of today and the future mainstream chemical industries have not fully embraced green chemistry and engineering with over 98% of organic chemicals being derived from petroleum.

This branch in Chemistry is still fairly new and will likely be one of the most important fields in the future.

By Khushleen Kaur

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