Beyond the Molecular Frontier Challenges for Chemistry and Chemical Engineering (2003) / Chapter Skim
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3 Synthesis and Manufacturing: Creating and Exploiting New Substances and New Transformations
3 Synthesis and Manufacturing: Creating and Exploiting New Substances and New Transformations
Pages 22-40
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From page 22... ...
Synthesis and Manufacturing: Creating and Exploiting New Substances and New Transformations 22
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From page 23... ...
As part of basic science, chemists have created new substances to test theories. For example, the molecule benzene has the special property of "aromaticity," which in this context refers to special stability related to the electronic structure of a molecule.
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From page 24... ...
In both synthesis and chemical manufacturing there is a general need to develop separation methods as well as synthesis methods. Until every synthetic reaction is perfect with respect to atom economy, so no side-products are formed, and by performing the reaction without added solvents or catalysts it is necessary to isolate the desired product and purify it.
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From page 25... ...
It is also true if the reaction is not perfectly selective, and additional undesired products are formed. In most cases, the extra chemicals produced in displacement or elimination reactions or in nonselective reactions must be removed, and disposing of them adds cost and the potential for environmental problems (see Chapter 9 for further discussion of related matters)
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From page 26... ...
Some manufacturing processes use the special properties of zeolites, inorganic substances that have interconnected cavities of well-defined size and shape. Reactions can be catalyzed inside the cavities, and they are normally selective for the shape of the substrate that can enter the cavities, and for the shape of the
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From page 27... ...
The modern reactions that make this possible are being invented by chemists involved in basic discovery and creation, usually in universities. The pressure on industrial process chemists to develop practical schemes for manufacturing important products means that they do not normally have the time for the basic research that can lead to new chemical reactions.
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From page 28... ...
Recently chemists and other scientists have been able to create new superconducting materials based on inorganic ceramics, which have considerably higher superconducting transition temperatures than the materials of Bednorz and Muller. Since synthesis is such a central part of chemistry and chemical engineering, many other Nobel Prizes have recognized synthetic achievements.
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From page 29... ...
Within chemistry, synthetic chemists will increasingly make use of the special properties of metal-based catalysts, both solid and as soluble complexes, to devise new transformations that are selective and efficient. Chemical engineers are increasingly involved in product design, in addition to process design, requiring the integral participation of the chemical engineer in the molecular conception and design of the products.
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From page 30... ...
Just as there is an explicit expectation that there will be a constant evolution and improvement of the software and the operating systems that drive our computers, so should the chemical community expect that there will be constant improvement and evolution of the armament of methodologies available for the practicing preparative chemist and the chemical industries. An explicit goal of the chemical community should be to make continual improvements in synthetic methodology, thereby expanding the range of challenging molecules that are accessible to practical synthesis.
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From page 31... ...
In pharmaceutical chemistry, the library of products is put through biological screens, usually automated, to determine whether any of the products binds particularly well to an enzyme of interest or to another biological receptor. When one product has been identified as a good binder, normal synthetic procedures are used to make enough for thorough testing.
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From page 32... ...
This is true in the new areas of nanoscience and nanotechnology, where synthesis is needed to make organized arrangements of many chemical components nanostructures with the distant goal of making tiny molecular machines and even molecular scale computers. Integration is also exploited as chemists begin to synthesize organized structures that imitate some of the properties of living cells.
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From page 33... ...
An even more desirable goal, difficult to reach currently, would be to develop chemical systems that could vary their own structures in a drive to produce the optimum of some desired property such as catalytic potency or strength of binding to a receptor. Such a chemical system could optimize itself according to the needs of humankind.
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From page 34... ...
Also, by the very nature of chemical transformations, there are almost always unused chemicals remaining. These chemical leftovers include contaminants in the raw materials, incompletely converted raw materials, unavoidable coproducts, unselective reaction by-products, spent catalysts, and solvents.
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From page 35... ...
Other novel reactor technologies include microwave reactors that have the objective of reducing the energy use and bulk temperature of reaction mixtures by performing selective heating on the particles of the catalyst. Novel separations technologies include membrane absorption and membrane distillation, centrifugal distillation columns, and simulated moving bed absorbers.
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New methods will need to be developed exploiting new phenomena to increase the intrinsic rates of mass transfer (for reactors and separations devices) , heat transfer (again associated with separations and reactions devices)
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SYNTHESIS AND MANUFACTURING 39 Aqueous Solution ~ . Containing Bisulfite Anion Enzyme in ~ Microporous Hollow-fiber Membrane , ~ (2R, 3S)
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From page 40... ...
The development and implementation of techniques will be critical for all aspects of chemical manufacturing from synthesis and analysis to optimization, evaluation, design, control, supply-chain management scheduling, and operation of chemical process systems. This will need to be done in a way that is consistent with societal and economic objectives and constraints.
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