Process chemistry automation

The issue of parallel versus sequential synthesis using multimode or monomode cavities, respectively, deserves special comment. While the parallel set-up allows for a considerably higher throughput achievable in the relatively short timeframe of a microwave-enhanced chemical reaction, the individual control over each reaction vessel in terms of reaction temperature/pressure is limited. In the parallel mode, all reaction vessels are exposed to the same irradiation conditions. In order to ensure similar temperatures in each vessel, the same volume of the identical solvent should be used in each reaction vessel because of the dielectric properties involved [86]. As an alternative to parallel processing, the automated sequential synthesis of libraries can be a viable strategy if small focused libraries (20-200 compounds) need to be prepared. Irradiating each individual reaction vessel separately gives better control over the reaction parameters and allows for the rapid optimization of reaction conditions. For the preparation of relatively small libraries, where delicate chemistries are to be performed, the sequential format may be preferable. This is discussed in more detail in Chapter 5. 

Blagden, N., and Davey, R., Polymorphs take shape, Chem. in Brit., March 1999, p. 44. Owen, M., and Dewitt, S., Laboratory Automation in Chemical Development. In Process Chemistry in the Pharmaceutical Industry (K.G. Gadamasetti, ed.), Marcel Dekker, Inc., New York 1999, pp. 429-455 Conner, K., The drive to improve the bottom line. Today s Chemist at Work, November 1999, p. 29. Sullivan, M., Automation accelerates synthesis. Today s Chemist at Work, September 1999, p. 48. Studt, T., Raising the bar on combinatorial discovery, Drug Discovery Development, January/February 2000, p. 24. Harness, J.R., Automated sample handling supports synthesis and screening. Drug Discovery Development, January 1999, p. 69. 

In addition to being necessary for all forms of life, biopolymers, especially enzymes (proteins), have found commercial applications in various analytical techniques (see Automated instrumentation, clinical chemistry Automated instrumentation, hemtatology Biopolymers, analytical techniques Biosensors Immunoassay) in synthetic processes (see Enzyme applications, industrial Enzyme applications in organic synthesis) and in prescribed therapies (see Enzyme applications, THERAPEUTICS IMMUNOTHERAPEUTIC AGENTS Vitamins). Other naturally occurring biopolymers having significant commercial importance are the cellulose (qv) derivatives, eg, cotton (qv) and wood (qv), which are complex polysaccharides. 

A number of automatic peptide synthesizers are commercially available now 40). However, in spite of all these mechanical and electronical advances in the automation of solid phase synthesis, as Barany and Merrifield state in their review on the solid phase peptide synthesis11), the limiting factor continues to be the chemistry of the process and automation can reach its full potential only when the assorted chemical difficulties are under control. 

Owen, M. Dewitt, S. Laboratory automation in chemical development. In Process Chemistry in the Pharmaceutical Industry Gadamasetti, K.G., Ed. Marcel Dekker, Inc. New York, 1999 429-455. 

New chapter on combinatorial chemistry that includes a discussion ot how the process is automated, recognizing that the search for new drugs often involves both synthesis and screening of large numbers of compounds... 

Although environmental and energy considerations have had considerable impact on the textile dyeing and finishing industry, the emphasis in the recent past has been on equipment modification rather than new chemistry. This trend can be expected to continue as more and more dyeing and finishing processes are automated and process control is substantially improved. 

Automated synthesis can ran unattended and is less prone to human error than manual synthesis. As the biopolymer assembly process was automated, there was a tendency to produce longer sequences. This, in turn, required better synthetic methods, which has led to continual improvements in solid-phase chemistries and instrument design. 

In chemistry and chemical engineering, expert systems are used for various tasks ranging from laboratory automation or reaction kinetics to the design of syntheses or the simulations of processes [24]. The application of expert systems in chemistry is described in more detail in Chapter IX, Section 2 of the Handbook,... 

One class of Al-based computational chemistry programs are de novo programs. These programs generally try to efficiently automate tedious tasks by using some rational criteria to guide a trial-and-error process. For example. 

Zinc. The electrowinning of zinc on a commercial scale started in 1915. Most newer faciUties are electrolytic plants. The success of the process results from the abiUty to handle complex ores and to produce, after purification of the electrolyte, high purity zinc cathodes at an acceptable cost. Over the years, there have been only minor changes in the chemistry of the process to improve zinc recovery and solution purification. Improvements have been made in the areas of process instmmentation and control, automation, and prevention of water pollution. 

---