Introduction to Green Chemistry
It is well known that the quality of life on earth became much better due to the discovery of dyes, plastics, cosmetics and other materials. The life expectancy rose from 47 years in 1900 to about 75 years in 1990’s.
The world’s food supply also increased enormously due to the discovery of hybrid varieties, improved methods of farming, better seeds, use of insecticides, herbicides and fertilizers. The advancement of technology led to new manufacturing processes/industries for the production of newer drugs, medicines and other materials. For all these, chemistry or chemical processes are responsible. It has already been stated (sec. 4.3.1, 6.4.2; 9.3) that virtually all industrial manufacturing processes are responsible for environmental pollution including pollution of air, water and land. This is attributed mainly to the effects of by- products of chemical industry and industrial effluents, which are being discharged into air, rivers/oceans and the land.The pollution reached such levels that various governments all over the world made laws to minimize it (see chapter 14). This marked the beginning of green chemistry in the middle of 20th century.
Green chemistry is defined as environmentally benign chemical synthesis. The synthetic procedures are designed in such a way that there is virtually no pollution to the environment. We know that as on today, maximum pollution to the environment is caused by numerous chemical industries. The cost involved in the disposal of the waste or by-products is also enormous. In view of this, it is most advantageous to design synthesis for manufacturing processes in such a way that the waste products are minimum and that these should have no effect on the environment. Also, the disposal of the waste products, if any, should be convenient. With this view in mind, the synthetic procedures should be designed
in such a way that the starting materials are used up to the maximum extent to give the final product. The reactions should not generate any toxic by-products.
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