Selectivity discussion

We propose that a relatively small number of watershed sites be established for intensive monitoring. These sites should be selected based on the criteria for site selection discussed previously (see Section 2.1.3). In particular, these sites should be located in areas that ... 

In this chapter the theory and practice of limiting-current technique for the measurement of mass-transport coefficients have been described. The selective discussion and tabular compilation of results of investigations that used limiting-current measurements should be indicative of the widespread use of this relatively novel method. 

The Co system is more reactive as well as much more selective than the Ni and Rh catalyst systems (Table XVII). The best systems allow almost 100% conversion with almost 100% yield of c -l,4-hexadiene. The best of the Ni and Rh systems known so far are still far from such amazing selectivity. The tremendous difference between the Ni system and the Co or Fe system must be linked to the difference in the nature of the coordination structures of the complexes, i.e., hexacoordinated (octahedral complexes) in the case of Co and Fe and tetra- or penta-coordinated (square planar or square pyramidal) complexes in the case of Ni. The larger number of coordination sites allows the Co and Fe complex to utilize chelating phosphines which are more effective than monodentate phosphines for controlling the selectivity discussed here. These same ligands are poison for the Ni (and Rh) catalyst system, as shown earlier. 

It is not intended to present in this article a comprehensive treatment, but rather, to illustrate applicable options available to the carbohydrate chemist and biochemist. Protecting groups introduced in other areas of chemistry that can be useful to the carbohydrate chemist will be selectively discussed. 

This chapter does not intend to be another exhaustive review of all work done to date or in recent years. We rather attempt to direct attention to still existing problems and hope to contribute to a better appreciation of these problems. We believe that the slow progress of MIP methods in the direction of practical applications has been partly due to the lack of a clear and systematic discussion of some of the problems encountered. Two important topics of this kind are the peak shapes in MIP HPLC, SPE, and CEC, and the problems with defining MIP selectivity. Discussion of these topics requires appreciation of some elements of nonlinear chromatography, which will be presented in this chapter. 

The presentation of the literature survey will depend upon the type ofproject being undertaken, e.g. laboratory based or a theoretical study. The presentation will also depend upon the number of publications to be discussed, i.e. a few papers can be reviewed in detail whereas a large number of publications (usually) require more selective discussion. 

Frequently the mobile phase is a mixture of liquids chosen and optimized by trial and error because results can be obtained so quickly and easily. The principles of mobile phase selection discussed in the last chapter are, of course, relevant. For normal phase systems on silica gel, a nonpolar... 

Third, the relative intensities of the Si(nAl) signals in realuminated samples are strikingly different from those in the as-prepared zeolites with the same framework composition, which means that the distribution of Si and A1 in the treated zeolites is different. This is a consequence of the different site selectivities discussed above, but also of the fact that both the original Si(OAl) sites and the Si(OAl) sites created during ultrastabilization are available for A1 substitution. 

Since eliminations cover a very wide spectrum of chemical reactions, this chapter is a selective discussion of the subject. The mechanistic basis of (3-eliminations is discussed, largely with reference to dehydrohalogenation, and a variety of a-eliminations are included here. Other eliminations, such as dehalogenation, are described throughout later chapters with reference to specific syntheses. 

Next, the chief designer marks those documents that are probably affected by the initial modifications. The selection discussed in 1. above occurs only within the FBW. However, the selection also covers other documents such as those of the simulations. 

The monocyclic substrates are well suited for discussion of relative stereocontrol. In a recently reported study employing cis- and rrar -disubstituted substrates (9) and (10). high stereoselectivity could be obtained when gallium trichloride was used as the Lewis acid (Scheme 12). In these reactions new stereocenters can be created at C(3) and C(3a). In the cis series both tautomeric products were formed as single stereoisomers while the trans series (10) produced a mixture of the tetrasubstituted isomers. A post facto epimerization was suggested as the cause for the lower selectivity. Discussion of the rotational sense is not warranted here as the configurations of the newly created centers were not rigorously established. 

Compare and contrast the MDR and MRPl with respect to structure, function, and drug selectivity. Discuss some of the unwanted potential consequences when we try to inhibit MDR to overcome drug resistance. 

For selected discussions on solid-phase organic synthesis, see the Handbook of Combinational Chemistry, Vo is. 1 2 (Eds. K. C. Nicolaou, R. Hanko, W. Hart-wig), Wiley-VCH, Weinheim, 2002, p. 1114. 

Space limitations do only allow a rather selective discussion. For further information, the reader is referred to review articles [13,18-24). 

The 3,4-0-acetal was more interesting as with simple alcohols it showed excellent p-selectivity and retained modest (3-selectivity even with hindered secondary alcohols (Scheme 40) [48]. This selectivity, of course, stands in stark contrast to the high a-selectivity discussed above for the 3,4-0-bisacetal protected... 

Colorimetric sensors are sensors in which binding of an anion results in a visible color change. They are a particularly attractive form of anion sensor as qualitative results can be achieved through naked eye sensing which does not require any equipment. There have been many examples of small molecule colorimetric sensors with a selection discussed below to give a flavor of the concepts which can be used when designing receptors. 

The book selectively discusses operations not extensively covered in readily available publications. These operations are usually covered by proprietary safety standards and operating procedures which are not generally accessible to the public. The book cannot possibly include every conceivable safety fundamental and therefore focuses on the more obvious and more frequently occurring operations. 

One can see that the use of the polar selectivity creates a grouping of the columns that is distinctly different from the classification by silanol activity. This demonstrates that column selectivity is truly multidimensional. Here, we have discussed three dimensions, while Snyder [4—9] deals with five dimensions. In our treatment, other dimensions are possible as well, for example the extended polar selectivity discussed in Ref. [13]. However, we believe that the three dimensions discussed here represent the strongest influences on column selectivity. 

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