Specific types, reagents

Procedures used in a laboratory must be recorded for easy reference, down to the smallest detail. An analytical laboratory will often use standard procedures from official publications, but to these must be added references to specific types of equipment used. As a result, a laboratory needs its own procedure manual to use in day-to-day work. Every operation should be described in detail, with references made to official methods where applicable. It takes thought and skill to write such a manual in a manner that will make is useful to all workers. Safety measures, where needed, must be included. Simple operations, such as the preparation of reagent solutions, should be specified. 

Several recent reviews have included specific types of electrophilic cyclofunctionalization reactions.1 Important areas covered in these reviews are halolactonization u cyclofunctionalization of unsaturated hydroxy compounds to form tetrahydrofurans and tetrahydropyrans lb cyclofunctionalization of unsaturated amino compounds lc cyclofunctionalization of unsaturated sulfur and phosphorus compounds ld lf electrophilic heterocyclization of unconjugated dienes 1 synthesis of y-butyrolactones 1 h synthesis of functionalized dihydro- and tetrahydro-furans lj cyclofunctionalization using selenium reagents lk lm stereocontrol in synthesis of acyclic systems 1" stereoselectivity in cyclofunctionalizations lP and cyclofunctionalizations in the synthesis of a-methylenelactones.lq Previous reference works have also addressed this topic.2... 

Although the topic of speciation is now a major focus of research and application it is not a new one. To give but one example, soil scientists have, for many decades, carried out a type of speciation in which specific selective reagents have been used to extract from soil that portion of an element known from field experiments to correlate with plant availability. A host of methodological approaches to speciation is now available and this edition attempts to provide an up-to-date documentation of the state-of-the-art as we enter the new millennium. 

Perhaps the toxoid research programs now being carried out in many research laboratories will provide a wide spectrum of toxoids for many different infectious diseases. Most of these toxoids should be prepared by specific-affinity-type reagents, including the suicide type, for the offending toxin from bacterial or viral agents. 

The emulsifier is not required specifically to obtain polybutadiene in water medium, but the reactivity of the system is affected by the nature of the emulsifier, the nonionic-type reagents producing best results. 

Specific derivatizing reagents take advantage of distinctive chemical characteristics of those solutes of interest and thus, generate colored or detectable derivatives of only those pertinent materials. Specific derivatization has two advantages firstly it only renders visible those solutes that are of interest and secondly, the solutes do not need to be completely separated from other materials that are of different chemical type because they will not appear in the separated mixture. 

Several problems first had to be overcome and several relevant questions to be answered before specific types of reactions could be approached. Among such problems and questions were those concerning the description of the different organometallic species in solution in a variety of solvents (see e.g., Chapter 13) the purity of the material, including the quality of the magnesium used for the preparation of the reagents and the identity of the different products formed during the reactions. 

In each of these studies the siterproduct relationship was determined on the basis of product distribution data obtained from standard, steady state catalytic reactions. While this approach can provide evidence for the type of site(s) responsible for the formation of certain products it cannot give any indication of the number of such sites that are present on the catalyst surface. Since the activities of the various types of sites are different, it is possible that a small number of very active sites could dominate product formation. In order to relate the extent of produet formation with the number of specific types of sites present an experimental arrangement is needed which obviates these site activity differences. One way of doing this is to use the catalyst surface as a stoichiometric reagent so that each site reacts only once. In this way there will always be a 1 1 site product molecule ratio regardless of the rates at which the different types of sites react. 

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