General experimental guidelines

The nature of the zinc (dust, foil, or shots) is important for the success of the formation of an organozinc halide by oxidative addition. Usually, the use of zinc dust (-325 mesh) from Aldrich or Riedel de Haen gives the best results. In some cases, such as for the preparation of allylic zinc halide reagents,22,28 iodomethylzinc iodide,65 or benzylic zinc halides,66 the use of zinc foil (0.1 mm or 0.25 mm thick, Aldrich or Merck) may be advantageous or even essential. 

Activation of zinc dust in THF with 1,2-dibromoethane and trimethylsilyl chloride 

Weigh the zinc dust into the three-necked flask, add THF (20 mL), and flush the flask with argon. 

2-dibromoethane and heat gently with a heat gun allowing boiling of THF. Allow to cool to rt. Repeat this heating-cooling process four more times. 

Add Me3SiCI and stir the reaction mixture for 15 min at rt. The zinc dust is now activated and ready for use. 

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Organozinc chemistry an overview and general experimental guidelines... 

GENERAL EXPERIMENTAL GUIDELINES FOR ASYMMETRIC PHASE-TRANSFER REACTIONS... 

As mentioned earlier (p. 11), the Monographs are not intended to summarize all published studies. Those studies in experimental animals that are inadequate (e g., too short a duration, too few animals, poor survival see below) or are judged irrelevant to the evaluation are generally omitted. Guidelines for conducting adequate long-term carcinogenicity experiments have been outlined (e.g. Montesano et al, 1986). 

Chemical mixture experiments have distinct characteristics that can preclude the use of traditional statistical analysis techniques. Mixture experimentation often poses unique exploratory questions that can be answered efficiently and economically with non-traditional statistical techniques. General statistical guidelines stress the importance of design, preliminary studies, action levels of variables, graphics, and appropriate statistical testing. Fractional ctorial and Simplex designs are just two of many statistical tools that are useful for analyses of mixture experiments. 

The first consideration is the choice of model system, and this may involve an aqueous electrolyte or nonaqueous media such as an organic electrolyte or molten salt. The selection of electrolyte and scavenger will depend on the energetics of the electrolyte reduction (good stability to reduction is needed) and upon the acceptor reactivity. Apparatus and electrochemical cells for metal/ electrolyte and semiconductor/electrolyte systems are similar generally. Some guidelines are presented below to assist with experimental practice (see also Chapter 3 in Ref. 10). Theses, also, are a good source of practical information, e.g., Refs. 20, 21, and 81. 

Generally, all praetieal reaetions oeeur by a sequenee of elementary steps that eolleetively eonstitute the meehanism. The rate equation for the overall reaetion is developed from the meehanism and is then used in reaetor design. Although there are eases where experimental data provide no information about intermediate ehemieal speeies, experimental data have provided researehers with useful guidelines in postulating reaetion meehanisms. Information about intermediate speeies is essential in identifying the eorreet meehanism of reaetion. Where many steps are used, different meehanisms ean produee similar forms of overall rate expression. The overall rate equation is the result... 

Separations for removing undesirable by-products and impurities, and making suprapure fine chemicals constitute a major fraction of the production costs. There is an enormous variety of methods for product separation and purification and many books on the subject have been published. Here, we deal with the problem in a very general way and we refer the reader to advanced books for details. Conventional techniques for product isolation and purification, such as fractional distillation, extraction, and crystallization, still predominate. Some guidelines for scale-up of these techniques and producing experimental data for scale-up are given in Chapter 5. More information on specific separation and purification techniques applied to particular problems of fine chemicals manufacture the reader can find in Chapter 6. 

In the general introduction to the EU test guidelines for toxicity (Part B), the following dehnition is provided Repeated dose/sub-chronic toxicity comprises the adverse effects occurring in experimental animals as a result of repeated daily dosing with, or exposure to, a chemical for a short part of their expected life-span. ... 

Using this approach, general guidelines for experimental design of C-tracer studies with MS could be shown for the central metabolism of Corynebacterium glutamicum comprising various flux scenarios and tracer substrates [26]. 

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