Site selection utilities

The most logical suming point in tlie safety design approach is to select a site where tlie number of undesirable weather and topograpltic conditions is limited. Adequate utilities and support systems plus fire protection service arc also required for a safe eiiviromnent. Chapter 5 presented a detailed account of phuit site selection and layout. These features will now be considered from a safety point of view. The following guidelines should be observed in dctcrniining a site tliat is favorable for tlie efficient tuid economical operation of the process. 

Complexation has been utilized to control site selectivity. The iron tricarbonyl complex 216 reacts with nitrile imines only at the cyclobutene double bond, whereas the uncomplexed analogue reacts at all three sites (117). 

An approach for the generation of secondary structure specific abzymes, which utilized a chimeric construction as the hapten, has been described. 98 The hapten was designed to elicit a catalytic antibody which could potentially site-selectively cleave a peptide bond. The synthesis of the hapten 48 is outlined in Scheme 23. 

Substitution of the hydrogen of many other aromatic compounds is controllable, but the problem of site selectivity still limits the synthetic utility of this reaction (Table 9). In an attempt to improve selectivity the fluorination of chlorobenzene was investigated in the presence of Lewis acids (Table 10). The addition of the Lewis acid is found to increase both conversion and selectivity. The best results are obtained in the presence of 0.9 equivalents of boron trichloride the effect of the boron trichloride is explained by the formation of a complex 7 with the fluorine, which is the fluorinating species. Large amounts of Lewis acid are required due to the formation of a stable complex between the boron trichloride and the fluoride formed as the fluorination progresses which effectively removes the catalyst from the system. ... 

This seminal observation has recently been utilized by Yamamoto to develop an approach for the stereoselective and site selective addition of organometallics to carbonyl substrates. The approach makes use of the very bulky aluminum reagent (1), which is readily prepared in situ by exposure of trimethyl-aluminum to a toluene solution of 2,6-di-f-butyl-4-alkylphenols (molar ratio 1 2) at room temperature. 

The routes toward improved design should start at the microscopic level, for example, via site-selective electrochemical deposition of Pt at the active three-phase boundary [146]. At this point, it is hard to estimate extra efforts to be invested in such procedures, but their prospects for optimized catalyst utilization are obvious. 

Level of protection 2 (LP-2) is a high-level passive protection that does not utilize sensors. Options for achieving LP-2 include site selection, addition and upgrade of filters and adsorption units specific to biological and chemical threats, compartmentalization and overpressurization of building interiors, filtration of outdoor air, relocation of outdoor air intake vents, local air-washes,2 security protection in the surrounding area, and appropriate operational responses. 

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