Sources of Configuration

Molecules with a single stereocenter as the only source of configurational stereoisomerism can exist as one of two enantiomers no configurational diastereomers are possible. Molecules with two dissimilar stereocenters can exist as one of four stereoisomers. Figure 8 outlines the relationships among these four stereoisomers. 

System and system design concepts — system of systems sources of configuration (product-process-resource) sources of configuration (public policies) configuration problems configuration models —> configuration solutions... 

Whether an element is the source of the cation or anion in an ionic bond depends on several factors for which the periodic table can serve as a guide In forming ionic compounds elements at the left of the periodic table typically lose electrons giving a cation that has the same electron configuration as the nearest noble gas Loss of an elec tron from sodium for example yields Na which has the same electron configuration as neon... 

Although safety interlocks can inappropriately initiate shutdowns, the process interlocks are usually the major source of problems. It is possible to configure so many process interlocks that it is not possible to operate the plant. 

This data may be needed to trace the source of any problems with product which was produced using this equipment. To take corrective action you will also need to know the configuration of the process plant at the time of processing the product. If only one piece of equipment is involved, the above records will give you this information but if the process plant consists of many items of equipment which are periodically changed during maintenance, you will need to know which equipment was in use when the fault is likely to have been generated. 

Identify potential sources of strong blast present within the area covered by the flammable cloud. Potential sources of strong blast include —extended spatial configuration of objects such as process equipment in chemical plants or refineries and stacks of crates or pallets ... 

End-suction and multi-stage pumps with in-line impellers are prone to excessive axial thrusting. In the end-suction pump, the centerline axial inlet configuration is the primary source of thrust. Restrictions in the suction piping, or low suction pressures, create a strong imbalance that forces the rotating element toward the inlet. 

The Spencer blower in this example provides air to a drying process in a metal-coating line. Its configuration includes an end-suction inlet that is in-line with the shaft and a horizontal discharge that is perpendicular to the shaft. In this particular example, the source of the shaft deflection observed in the mode plot is aerodynamic instability. 

Of the four possible 5-deoxy-pent-4-enofuranoses, the D-erythro-isomer was of interest as a potential source of derivatives of L-lyxofuranose. For this purpose, a vinyl ether having the D-en/ hro-configuration has been prepared from derivatives of D-ribose. Condensation of D-ribose with acetone in the presence of methanol, cupric sulfate and sulfuric acid at 30°C., as described by Levene and Stiller(30) afforded a sirupy product consisting mainly of methyl 2,3-O-isopropylidene-D-ribofuranose (40). Treatment of a pyridine solution of the sirup with tosyl chloride... 

Divalent sulfur compounds are achiral, but trivalent sulfur compounds called sulfonium stilts (R3S+) can be chiral. Like phosphines, sulfonium salts undergo relatively slow inversion, so chiral sulfonium salts are configurationally stable and can be isolated. The best known example is the coenzyme 5-adenosylmethionine, the so-called biological methyl donor, which is involved in many metabolic pathways as a source of CH3 groups. (The S" in the name S-adenosylmethionine stands for sulfur and means that the adeno-syl group is attached to the sulfur atom of methionine.) The molecule has S stereochemistry at sulfur ana is configurationally stable for several days at room temperature. Jts R enantiomer is also known but has no biological activity. 

Corrections for gauche configurations and cis isomers are given in the footnotes to Table 6. Corrections for ring structures are given in Table 8. The sources of the ring correction terms are discussed in Section IV. 

Polymer stereochemistry, sometimes referred to as tacticity, is not the only source of variation in polymer configuration. For the monosubstituted butadiene isoprene, the structures shown in Figure 3.2 are possible. 

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