Accelerators chemistry

Dijkstra, H.P, van Klink, G.P.M, van Koten, G. (2002) The Use of Ultra- and Nanofiltration Techniques in Homogeneous Catalyst Recycling. Acceleration Chemistry Research, 35, 798-810. 

Accelerated Chemistry Microwave, Sonochemical, and Fluorous Phase Techniques... 

Accelerator Chemistry Workstation - Powerful and Versatile Solution for Chemistry Applications, Product Information, Chemspeed Ltd., Angst, Switzerland, August 2002. 

Lead drug compound synthesis using the current knowledge of medicinal chemistry represents a significant bottleneck in the discovery chain. MW-accelerated chemistry has proved to be invaluable for the pharmaceutical industry in reducing the timescale of this process. Therefore, pharmacentical companies have invested heavily in robot-assisted MW technology. The time saving associated with the use of MW-assisted accumulation of compound libraries was... 

One possible answer lies in the fact that positicMiing and proximity are important factors in chemical reactions [24]. Enzymes can find reactants even in relatively dilute solutions they accelerate chemistry, in part, by bringing reactants close to each other, increasing their effective concentration. Enzyme-catalysed reactions can occur at rates that would normally require very high concentrations of reactants in solutifMi. Enzymes often use tricks such as acid or base catalysis to achieve huge rate enhancements above spontaneous reactions, but substrate positioning is a part of what makes the chemistry work. 

Surfactants have also been of interest for their ability to support reactions in normally inhospitable environments. Reactions such as hydrolysis, aminolysis, solvolysis, and, in inorganic chemistry, of aquation of complex ions, may be retarded, accelerated, or differently sensitive to catalysts relative to the behavior in ordinary solutions (see Refs. 205 and 206 for reviews). The acid-base chemistry in micellar solutions has been investigated by Drummond and co-workers [207]. A useful model has been the pseudophase model [206-209] in which reactants are either in solution or solubilized in micelles and partition between the two as though two distinct phases were involved. In inverse micelles in nonpolar media, water is concentrated in the micellar core and reactions in the micelle may be greatly accelerated [206, 210]. The confining environment of a solubilized reactant may lead to stereochemical consequences as in photodimerization reactions in micelles [211] or vesicles [212] or in the generation of radical pairs [213]. 

The rates of several chemical reactions accelerate by factors of 10 or more between 0.1 and 100 MPa at ambient temperature, so much interesting chemistry occurs at these lower pressures. At such Tow pressures, Bridgman [26] even showed how to cook eggs at room temperature. 

Many globular proteins are enzymes They accelerate the rates of chemical reactions m biological systems but the kinds of reactions that take place are the fundamental reactions of organic chemistry One way m which enzymes accelerate these reactions is by bringing reactive func tions together m the presence of catalytically active functions of the protein... 

When the surface conditions are acidic or the ambient humidity is low enough to affect the cure significantly, a surface accelerator may be used to promote the reaction. Available from most manufacturers, these basic solutions may be dip, wipe, or spray appHed. Recentiy, new additive chemistry has been developed that accelerates the cure under adverse conditions without the need for a separate accelerator. 

A. B. Sullivan, C. J. Harm, and G. H. Kuhls, "Vulcanisation Chemistry— Fate of Elemental Sulfur and Accelerator during Scorch Delay as Studied by Modem HPLC", Paper No. 9, presented at the MGS Tubber Division Meeting Toronto, Canada, May 21 —24, 1991, American Chemical Society, Washington, D.C., 1991. 

Oxygen corrosion involves many accelerating factors such as the concentration of aggressive anions beneath deposits, intermittent operation, and variable water chemistry. How each factor contributes to attack is often difficult to assess by visual inspection alone. Chemical analysis of corrosion products and deposits is often beneficial, as is more detailed microscopic examination of corrosion products and wasted regions. 

Dealloying is influenced by many factors. In general, any process that increases general corrosion will promote dealloying. However, specific acceleration factors may be further classified into one of three categories metallurgy, environment, and water chemistry. 

Frequently a piece of equipment is used in different processes during its lifecycle. This could result in process conditions that exceed the safe operating limits of the equipment. Equipment inspection may provide a poor prediction of the equipment s useful life and reliability, due to the change of material handled or change in process chemistry over the life of equipment. Batch operations are also characterized by frequent start-up and shut-down of equipment. This can lead to accelerated equipment aging and may lead to equipment failure. This chapter presents issues and concerns related to the safe design, operation, and maintenance of various pieces of equipment in batch reaction systems, and provides potential solutions. 

Recent advances in accelerator technology have reduced the cost and size of an RBS instrument to equal to or less than many other analytical instruments, and the development of dedicated RBS systems has resulted in increasing application of the technique, especially in industry, to areas of materials science, chemistry, geology, and biology, and also in the realm of particle physics. However, due to its historical segregation into physics rather than analytical chemistry, RBS still is not as readily available as some other techniques and is often overlooked as an analytical tool. 

Microwave chemistry has been found to be a useful method for accelerating reactions or catalyzing reactions that are difficult to carry out by other methods. A modification of the Hantzsch method to directly obtain pyridines has been communicated. A dry medium using ammonium nitrate bentonitic clay system with microwave irradiation affords pyridines 96 in a single pot within 5 minutes. When the pyridine is not the major product (> 75% yield), the dealkylated pyridine 97 becomes an... 

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