Green Chemistry

By
Prof.Nagendrappa

The gardeners who have a knack for making plants grow are said to have a “green thumb”. It is a distinctive skill that makes plants bloom and flourish, by providing a nourishing environment through enrichment of the soil with minerals and nutrients.

Green is the colour of well-nourished, healthy flora with beautiful flowers and fruits interspersed. It is sign of a prosperous, benevolent environment. Industries cause environmental imbalance due to wastes they generate, particularly in and around their immediate vicinity. Industries in general, chemical industries in particular, damage the environment by throwing out waste products, whether hazardous or harmless.

However, because we cannot go back to old, industry-free era, the best we can do is to devise methods that are efficient in utilizing raw materials, energy, equipment and other resources, and at the same time strive to prevent or minimize wastes.
The present day chemical production methods are definitely amenable for modification or change to alternative processes that would have lesser negative impact on the “green character” of the environment. The chemical activity that strives to develop environmentally benign synthetic procedures is known as “Green Chemistry”.

Twelve principles of Green Chemistry

Anastas and Warner have defined Green Chemistry as “The utilization 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”. They have enunciated twelve guidelines as the principles of Green Chemistry. They are listed below,

• It is better to prevent waste than to treat or clean up waste after it is formed.
• Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
• Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
• Chemical products should be designed to preserve efficacy of function while reducing toxicity.
• The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
• 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.
• A raw material of feedstock should be renewable rather than depleting wherever technically and economically practicable.
• Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.
• Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
• Chemical products should be designed so that at the end of their function they do not persist in the environment and break don into innocuous degradation products.
• Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
• Substances and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires.