The first principle of Green Chemistry is PREVENTION. This prevention is at a molecular level and aims at minimising the amount of chemical waste produced in a reaction, as this is more efficient than cleaning up waste that has already been produced. The purpose of green is to produce the same amount of desired product as usual methods would, but with less of an effect to the environment, and prevention of waste is the first step in doing so.
THE PREVENTION PRINCIPLE
The E-factor is often referred to as a measure of waste or any other by-product produced by chemists BUT the desired product. More often than not this waste produced was seen as unavoidable, but Green Chemistry has allowed the production of the same amount of desired product with LESS waste!
PROCESS MASS INTENSITY
Process mass intensity - the ratio of total mass used in a process divided by the mass of the product.
Normally, the ratio of product to total mass used has been relatively small, causing the reactions used in many processes to result in a large amount of waste that may be detrimental to the environment.
However, when green chemistry is applied there is often a major decrease in the amount of waste produced with is obviously an important goal that has been achieved with the introduction of green chemistry to the industry.
An example of green chemistry that is used in the pharmaceutical industry is Ibuprofen, where in 1993 the processes of its production was reinvented using green chemistry.
The process begins with the exact same compound, however, the the process has been refined so instead of six steps involved, there are now only three. This new process produces slightly different drugs than previous methods, and these drugs can now be recycled.