Fischer projections configuration

Type Absolute configuration Absolute configuration Fischer projection formula... 

The sawhorse or Newman representations of 2-butanol, 5a and 5b and 6a and 6b, are excellent for showing the arrangements of the atoms in conformations, but are needlessly complex for representing the stereochemical configuration. Fischer projection formulas are widely used to show configurations and are quite straightforward, once one gets the idea of what they represent. 

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... 

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... 

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. 

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

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 ... 

Step 2 Place the group of lowest priority, usually H, at the top of the Fischer projection by using one of the allowed motions. This means that the lowest-priority group is oriented back, away from the viewer, as required for assigning configuration. 

Assign R or S configuration to the following Fischer projection of alanine ... 

Problem 25.4 Redraw the following molecule as a Fischer projection, and assign R or 5 configuration to the chirality center (yellow-green = Cl) ... 

Figure 25.2 Some naturally occurring D sugars. The -OF group at the chirality center farthest from the carbonyl group has the same configuration as

Absolute configuration (Section 9.5) The exact three-dimensional structure of a chiral molecule. Absolute configurations are specified verbally by the Cahn-Ingold-Prelog R,S convention and are represented on paper by Fischer projections. 

Fischer projection (Section 25.2) A means of depicting the absolute configuration of a chiral molecule on a flat page. A Fischer projection uses a cross to represent the chirality center. The horizontal arms of the cross represent bonds coming out of the plane of the page, and the vertical arms of the cross represent bonds going back into the plane of the page. 

Fischer projections and, 977-978 glycosides and, 989-990 l- 4 links in, 997-998 origin of name. 973 photosynthesis of, 973-974 see also Aldose, Monosaccharide vaccines from, 1004-1005 Carbon, ground-state electron configuration of, 6... 

Fischer projection, 975-978 carbohydrates and, 977-978 D sugars, 980 i., sugars, 980-981 rotation of, 976 R.S configuration of, 977 conventions for, 975-976 Fishhook arrow, radical reactions and, 139, 240... 

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