Green chemistry is the research and engineering of products and processes to minimalize the use of and production of hazardous substances. Green chemistry seeks to reduce and prevent pollution at its source.
The twelve principles of green chemistry were developed by Paul Anastas (who also coined the term ‘Green Chemistry’) and John C. Warner. The principles cover concepts such as:
* The design of processes to maximize the amount of raw materials used in the end product.
* The use of safe environmentally-friendly substances including solvents whenever possible.
* The design of energy efficient processes.
* A lack of waste product created in the process.
The twelve principles are:
1. It’s better to prevent waste than to treat/ clean up waste after it’s formed.
2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3. Wherever possible, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
4. Chemical products should be designed to preserve efficacy of function while reducing toxicity.
5. The use of auxiliary substances (e.g. solvents, separation agents) should be made unnecessary wherever possible and harmless when used.
6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.
7. A raw material or feed stock should be renewable rather than depleting wherever technically and economically practicable.
8. Reduce derivatives –unnecessary derivation (blocking group, protection/deprotection, and temporary modification) should be avoided whenever possible.
9. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
10. Chemical products should be designed so that at the end of their function they do not perish in the environment and break down into harmless degradation products.
11. 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. Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions or fires.
The atmosphere is made up of five main layers. These layers are called the Exosphere, the Thermosphere, the Mesosphere, the Stratosphere and the Troposphere. There are also five other layers that are distinguishable by other properties. These are called the Ozone Layer, the Ionosphere, the Homosphere, the Heterosphere, the Planetary Boundary layer.
The temperature decrease the higher the altitude through the troposphere but when the stratosphere starts the temperature increases again due to the heat within the ozone layer caused by UV radiation being absorbed by dioxygen and ozone gas in the stratosphere. In the thermosphere temperature also increases with altitude.
The Ozone gas in the Ozone layer reacts with other gases such as nitrogen, chlorine, bromine, oxygen and hydrogen. These reactions cause the natural catalytic cycle of the ozone layer.
In the stratosphere, an oxygen molecule photodissociates after absorbing an ultraviolet photon. This causes:
2O. + 2O2 2O3
O3 –UV-> O2 + O
O2 + O O3
O + O3 2O2
NOx is the genetic term for NO and NO2. NOx produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures. NOx in the atmosphere reacts to form smog and acid rain. It is also fundamental to the formation of