Waste minimization, green chemistry

I did not realize how much a single class wastes. Not much because we did such minimal green chemistry, but I now understand I am aware that organic reactions can occur in a greener manner. 

A green chemistry variation makes use of solventless conditions to minimize the waste stream from reactions of this type. To a mortar are added aldehyde 67, ketone 68 and solid sodium hydroxide. The mixture is ground and within 5 minutes aldol product 69 is produced. Addition of the second ketone and further grinding affords the 1,5-diketone 70, which can be isolated and cyclized to pyridine 71 with ammonium acetate. The authors report that this method can substantially reduce the solid waste (by over 29 times) and is about 600% more cost effective than previously published procedures. 

Green chemistry (Chapter 11 Focus On) The design and implementation of chemical products and processes that reduce waste and minimize or eliminate the generation of hazardous substances. 

As time passes and our awareness of our global environment increases, the world s populace becomes acutely cognizant of the detrimental effects resulting from human endeavors. Incorporated into its assessment of the success of its chemical activities, an environmental barometer will demonstrate the commitment of chemistry to the environment. Green chemistry has as its aim to conduct its chemical activities in such a way as to minimize the generation of waste and to continually increase the beneficial environmental effects relative to previous practices. 

Trends in mass spectrometry focus on the improvement of instrumentation, of several techniques in order to minimize sample volume, to improve sensitivity and to reduce detection limits. This is combined with increasing the speed of several analyses, with automation of analytical procedures and subsequently reducing the price of analysis. A minimizing of sample volumes means a reduction of waste volume with the aim of developing green chemistry . Furthermore, new analytical techniques involve a development of quantification procedures to improve the accuracy and precision of analytical data. Special attention in future will be given to the development of hyphenated mass spectrometric techniques for speciation analysis and of surface analytical techniques with improved lateral resolution in the nm scale range. 

An efficient way in green chemistry to achieve waste minimization is to replace processes requiring stoichiometric reagents by catalytic methods. This is a... 

In the previous section we saw that one of the key objectives of green chemistry is waste minimization. Moreover, we learned that a sustainable process is one that optimizes the use of resources, while still leaving sufficient resources for future generations. Catalysis is an important tool in both cases. In fact, as far as chemistry is concerned, catalysis is the key to sustainability [21]. 

Handbook of Green Chemistry and Technology, J. H. Clark and D. J. Macquarrie, Eds., Blackwell Publishing 2002, 540 pp., ISBN 0-632-05715-7. This collection of 22 review essays covers all the important areas of green chemistry, including environmental impact and life-cycle analysis, waste minimization, catalysts and their industrial applications, new synthesis methods, dean energy, and novel solvent systems. The chapters are well referenced and contain pertinent examples and case studies. 

Green chemistry reduces toxicity, minimizes waste, saves energy, and cuts down on the depletion of natural resources. It allows for advances in chemistry to occur in a much more environmentally benign way. In the future, when green chemistry is practiced by all chemists and all chemical-related companies, the term green chemistry will ideally disappear as all chemistry becomes green, see also Ibuprofen Industrial Chemistry, Organic Solution Chemistry. 

Another important goal of green chemistry is the utilisation of renewable raw materials, i.e. derived from biomass, rather than crude oil. Here again, the processes used for the conversion of renewable feedstocks - mainly carbohydrates but also triglycerides and terpenes - should produce minimal waste, i.e. they should preferably be catalytic. 

Ionic liquids (ILs) tend to have good thermal stability, they exhibit liquid ranges of up to 300° C, and because they have negligible vapor pressure, they do not evaporate—all of which explains their use as replacements for volatile organic compounds. This also makes them very easy to contain and transfer, and allows their use under high vacuum conditions. Another quite important aspect is that ILs can be recycled (often with associated catalysts dissolved in them) this considerably minimizes waste production in accordance with green chemistry, and it lessens expenditure in view of the high cost of many ILs compared with that of conventional solvents. 

---