green chemistry essay

green chemistry essay

The Importance and Principles of Green Chemistry

1. Introduction to Green Chemistry

Green chemistry can be used in all areas, in chemical production, in agriculture, in alternative medical treatments. All human activities should maintain the delicate balance for our environment to sustain life on the planet. In this transient time, many people are sued by US chemical companies and taken into court – including me. Many US courts have now ruled that toxic materials have a long lifetime, including pesticides often called ‘cides’ like suicide, matricide, fratricide – we are killing living things, and ‘bioallethrin’ in raid spray. No one on earth yet understands how all living things interact with the life support system; we must minimize damage to it. We tend to be quite unconscious of what we are doing, causing a toxic legacy. We must avoid leaving these toxic thoughts in the eon soil of our successors; this is what the precautionary principle is all about.

Green chemistry is defined as the practice of chemical science and technology to design greener, safer, and more sustainable products and processes. Green chemistry, also known as sustainable chemistry, results in a significant reduction of the use of hazardous chemicals, reduced wastes, and reduced energy. There are about 12 principles of green chemistry that are all meant to provide useful information regarding how to minimize the hazardous products of manufacturing reactions. It is very important to have these principles in mind because many of our industrial materials are toxic. Some, like nickel-cadmium batteries and plutonium, have very long half-lives. But there is a spectrum of half-life from many years, like the PCBs and the hexa-chlorinated dioxins and dibenzo-furans, to the half-life of lead from lead paint (over a century) and leaded gasoline (over 20 years). However concerned we are about global warming, toxic products concern us much more because they will cause immediate and direct harm and tend to be more widespread.

2. Key Principles of Green Chemistry

Chemical products should be designed to preserve efficacy of function while reducing toxicity. The use of renewable raw materials is an essential criterion in the design of green chemistry. Likewise, the use of waste materials as raw materials also contributes to a process being classified as green. By adhering to these principles, scientists can “build in” sustainability and environmental compatibility to the smallest of products.

(i) Waste Prevention. It is better to prevent waste than to treat or clean up waste after it has been created. Synthetic methods should be designed to generate less waste. (ii) Atom Economy. A synthetic method should be designed to maximize the incorporation of all materials used in the process into the final product. (iii) Less Hazardous Chemical Syntheses. Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment. (iv) Designing Safer Chemicals. Chemical products should be designed to effect their desired function while minimizing their toxicity. (v) Safer Solvents and Auxiliaries. The use of auxiliary substances should be avoided wherever possible and appropriate, and innocuous solvents should be used. (vi) Design for Energy Efficiency. Energy requirements should be recognized for their environmental and economic impacts. Synthetic methods should be conducted at ambient temperature and pressure.

Green chemistry is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances. In this section, we will introduce our readers to the aims and principles of green chemistry. Some of the key principles that define the scope of green chemistry include:

3. Applications and Benefits of Green Chemistry

Chemical reactivity can also be fine-tuned to direct product formation, pressures reduced, hazardous substances avoided, and factors affecting thermodynamics designed to facilitate downstream unit operations as part of Multistep synthesis and multicomponent reactions. Early-stage conceptual development of molecules and processes incorporating green principles has proved to be beneficial for the pharmaceutical and information storage sectors, and will therefore likely be important in other product areas. As composite materials, nanotube-filled rubbers are being used to improve the properties of vehicle tires and thermosets for various uses. The application of green chemistry principles in these systems will, in the future, lead to recycle-friendly systems. Unstated here is the current interest in bio-derived sources of carbon feedstock. These features lead to resource efficiency and pollution prevention and the need to use less energy and water and therefore reduce costs. This, together with the production of less wasted material, can lead to both cost competitiveness and public good manufacture. Indirectly and perhaps most importantly, it can improve the safety and durability of products, as well as the health of humans and the environment.

There was an immediate appreciation of the opportunities green chemistry offered in the pharmaceutical sector, due in no small part to the vulnerable intermediates that are often used in the synthetic approach, which lend themselves to conversion to the free chiral carbinol process, and the fact that the application of new routes has the potential to provide substances having novel revised isomers. The introduction of effective catalysts can then further catalyze the crystallization process, as witnessed through applications of enzymes in industrial processes used in the production of intermediates for statin drugs (Lipitor, Zocor, Crestor). Other demonstration processes have been applied in the synthesis of acrylates by a one-pot process that requires phenol in a finishing step to make a derivative of aspirin.

4. Challenges and Future Directions in Green Chemistry

There are a variety of factors that could impede the rapid spread of GC within industry. For example, it seems likely that there will be significant technological barriers to the development of many new, more environmentally benign processes. This is probably not simply a question of difficulty or cost but reflects limitations in the different types of chemistry that can be carried out under mild conditions. It is particularly interesting to note that in many cases, the most important application of environmentally benign base-metal oxidation catalysts is likely to be in process intensification and the move towards more continuous chemistry rather than in using ‘microwave’ synthesis. There are also a variety of economic barriers as to why greener chemistries may not be taken up. A key issue here is that the depreciation of capital plant can be an important part of the cost associated with a synthetic route. If a new molecule is accessed through a radically different process it and the associated plant may need to be approved by regulatory agencies as well as the molecules it contains. This may simply in practice be impossible and the costs of developing a new plant of certain vessels etc. almost certainly outweigh their residual value. At a more pragmatic level, many companies have sophisticated approaches for risk assessment and insurance and will explicitly place a ‘value’ on variety of risks including plant breakdown, which will likely be greater with process intensification than with traditional practices. Greener chemistries must at a most basic level seek to match some of the economic advantages offered by traditional chemistries with safer plant offering reduced insurance premia etc. but this is not as easy a task as it might sound. As practically all organic and much inorganic chemistry has already been scoped, greener reactions are often those that must focus activity in places where chemistry is often less well understood. Clearly, this can only be overcome by scientific research. Another crucial hurdle that must be overcome is the perception of green chemistry/catalysis by process chemists, engineers and chemical engineers. In order for chemists to adopt newer and possibly less stable solvents and reagents, they generally have to be shown that they are equal in performance to traditional solvents etc., but this alone is not sufficient in many scenarios.