Green alternatives

One of the major issues with fuel cells is the problem of hydrogen storage. A very large tank would be needed even with a compressed hydrogen tank. Other issues include carbon monoxide intolerance, overpotential at the anode and cathode, and internal resistance. We will be discussing these problems in greater detail in Chapter 12. 

Yergin, D. H. 1991. The prize The epic quest for oil, money, andpower, 597. New York Simon and Schuster. 

National Academy of Sciences. 1982. The competitive status of the U.S. auto industry in crisis a study of the influences of technology in determining international industrial competitive advantage, 10 (http //books.nap.edu/openbook.php record id=291 page=10). 

Japan Automobile Manufactures Association. Japan s auto industry (http //www.jama. org/about/industry 1 Ohtm) 

Census Bureau news release regarding median income (http //pubdb3.census.gov/ macro/032007/hhinc/new04 001 htm) 

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Carless, J. (1993). Renewable Energy A Concise Guide to Green Alternatives. New York Walker and Company. 

Biopolymers have diverse roles to play in the advancement of green nanotechnology. Nanosized derivatives of polysaccharides like starch and cellulose can be synthesized in bulk and can be used for the development of bionanocomposites. They can be promising substitutes of environment pollutant carbon black for reinforcement of rubbers even at higher loadings (upto SOphr) via commercially viable process. The combined effect of size reduction and organic modification improves filler-matrix adhesion and in turn the performance of polysaccharides. The study opens up a new and green alternative for reinforcement of rubbers. 

It is of primary interest to avoid corrosive mineral acids in synthetic processes. This can easily be achieved by use of acidic solid supports coupled with microwave irradiation. This has been applied to the preparation of quinolines [53] (Scheme 8.35). This procedure is a safe, green alternative to the use of H2S04 at more than 150 °C. In the same way, quinoxaline-2,3-diones were prepared [54] by use of single-mode irradiation. Previous attempts in solution led to explosions, but the authors successfully used solvent-free conditions with acidic supports or catalysts (the best being p-toluenesulfonic acid) and irradiation times of 3 min (Scheme 8.36). 

Earle, M. J., McCormac, P. B. Seddon, K. R. Diels-Alder reactions in ionic liquids a safe recyclable green alternative to lithium perchlorate-diethyl ether mixtures. Green Chem., 1999, 1(1), 23-25 Doherty, S. Goodrich, P. Hardacre, C. et al. Marked enantioselectivity enhancements for Diels-Alder reactions in ionic liquids catalysed by platinum diphosphine complexes. Green Chem., 2004, 6(1), 63-67. 

UV/EB processing has another positive side. They both represent a clean and efficient use of electric energy. When compared with water-based technology, another green alternative to VOC-based technology, it is found to be far superior in energy consumption (see Table 1.2). 

Differential Toxicity Characterization of Green Alternative Chemicals... 

Figure 7.14 Axially chiral natural products may provide a green alternative to BINOL.

Another interesting alternative combines catalysis and electrochemistry [35]. In the reductive coupling cycle of two bromobenzene molecules to biphenyl, the Pd catalyst provides just two electrons. This reaction can be performed in an electrochemical cell, where the electrons are supplied from an outside source [36]. We thus see that catalysis gives us a variety of green alternatives to the classic stoichiometric process. There are no hard and fast rules as to which route to choose - it all depends on the reaction conditions, and on the chemicals available. 

Regioselective reactions in systems which contain multiple functional groups are an area ideally suited for biocatalysis. Linhardt and co-workers at the University of Iowa s Division of Medicinal and Natural Products Chemistry recently published the synthesis of a series of 1 -O-acyl sucrose derivatives [31], Using Chiro-CLEC -BL (the CLC of subtilisin) and vinyl esters of the acylating agent in pyridine as solvent, the authors prepared l -O-lauryl sucrose, l -O-myristyl sucrose, and l -O-stearyl sucrose in 80-90% yield (Fig. 9). Their method represents a green alternative to the tin chemistry previously used [32],... 

Applications of photocatalytic oxidations as a green alternative synthetic route has been investigated by several authors although these reactions have always been considered as highly nonselective processes. 

It s important to gas out new clothing and to wash new items a number of times before wearing them. Most clothing is treated with many chemicals, such as pesticides on the cotton, bleach, synthetic paint, treatments in the production process and in the transportation containers, and so on. You should definitely not wear clothing that has just come from the dry cleaner, unless the dry cleaner does not use harmful chemicals, in which case the clothes are probably safe for MCS patients sooner. Be careful and well informed if you want to use this green alternative. Green does not necessarily mean it is also tolerable or safe for MCS patients. See Part VI for web addresses on this subject. 

In addition, the above-discussed photochemical methods can be thought of as offering a dean (or green ) alternative method [84,85], which represents an active area of current research. 

Cesium-exchanged zeolite X was used as a solid base catalyst in the Knoevenagel condensation of benzaldehyde or benzyl acetone with ethyl cyanoacetate [121]. The latter reaction is a key step in the synthesis of the fragrance molecule, citronitrile (see Fig. 2.37). However, reactivities were substantially lower than those observed with the more strongly basic hydrotalcite (see earlier). Similarly, Na-Y and Na-Beta catalyzed a variety of Michael additions [122] and K-Y and Cs-X were effective catalysts for the methylation of aniline and phenylaceto-nitrile with dimethyl carbonate or methanol, respectively (Fig. 2.37) [123]. These procedures constitute interesting green alternatives to classical alkylations using methyl halides or dimethyl sulfate in the presence of stoichiometric quantities of conventional bases such as caustic soda. 

This one-pot process, performed in water, is clearly an attractive, green alternative to the above-mentioned BASF process. Unfortunately, high enantioselec-tivities are obtained only with amine substrates containing an aromatic moiety. 

Another green alternative is the use of photocat-alytic processes, which involve photochemical activation of semiconductors working as catalysts for redox processes that efficiently transform organic or inorganic pollutants into less dangerous substances. 

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