Fischer configuration

To verify that the Fischer jjrojection has the R configuration at its chirality center rotate the three dimensional representation so that the lowest ranked atom (H) points away from you Be careful to maintain the proper stereochemical relationships during the operation... 

What IS the absolute configuration (/ or S) of the compound rep resented by the Fischer projection shown here ... 

Write the Fischer projection of the (-) 2 octanol formed from it by nucleophilic substitution with inversion of configuration... 

Make a molecular model corresponding to the stereochem istry of the Fischer projection of 2 phenyl 2 butanol shown in the equation and verify that it has the R configuration... 

Notice that the eclipsed conformation of d ribose derived directly from the Fischer pro jection does not have its C 4 hydroxyl group properly oriented for furanose ring forma tion We must redraw it m a conformation that permits the five membered cyclic hemi acetal to form This is accomplished by rotation about the C(3)—C(4) bond taking care that the configuration at C 4 is not changed... 

Glycine is the simplest ammo acid and the only one m Table 27 1 that is achiral The a carbon atom is a chirality center m all the others Configurations m ammo acids are normally specified by the d l notational system All the chiral ammo acids obtained from proteins have the l configuration at their a carbon atom meaning that the amine group IS at the left when a Fischer projection is arranged so the carboxyl group is at the top... 

Thiol (Section 15 13) Compound of the type RSH or ArSH Th reo (Section 7 11) Term applied to the relative configuration of two stereogenic centers within a molecule The threo stereoisomer has like substituents on opposite sides of a Fischer projection... 

A simpler representation of molecules containing asymmetric carbon atoms is the Fischer projection, which is shown here for the same lactic acid configurations. A Fischer projection involves... 

The diirality of a molecule is described by specifying its configuration. The system that is used is the Cahn Ingold-Prel6g convention, which uses the descriptors R and S. The Fischer convention, employing the descriptors D and L, is historically important and is still used with certain types of molecules. 

Sometimes the terms erythro and threo are used to specify fee relative configuration of two adjacent stereogenic centers. The terms are derived fom fee sugars erythrose and threose. The terms were originally defined such feat a Fischer projection formula in which two adjacent substituents were on the same side was fee erythro isomer and feat in whidi the substituents were on opposite sides was the threo isomer. 

Switching the positions of two groups in a Fischer projection reverses the configuration of the chirality center. 

Relative to each other, both hydroxyl groups are on the same side in Fischer projections of the erythrose enantiomers. The remaining two stereoisomers have hydroxyl groups on opposite sides in their Fischer projections. They are diastereomers of d- and L-erythrose and are called d- and L-threose. The d and l prefixes again specify the configuration of the highest numbered chirality center. D-Threose and L-threose are enantiomers of each other ... 

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