Enantiomer modeling molecule

The property of chirality is determined by overall molecular topology, and there are many molecules that are chiral even though they do not possess an asymmetrically substituted atom. The examples in Scheme 2.2 include allenes (entries 1 and 2) and spiranes (entries 7 and 8). Entries 3 and 4 are examples of separable chiral atropisomers in which the barrier to rotation results from steric restriction of rotation of the bond between the aiyl rings. The chirality of -cyclooctene and Z, -cyclooctadiene is also dependent on restricted rotation. Manipulation of a molecular model will illustrate that each of these molecules can be converted into its enantiomer by a rotational process by which the ring is turned inside-out. ... 

Let s return to bromochlorofluoromethane as a simple example of a chiral molecule. The two enantiomers of BrCIFCH are shown as ball-and-stick models, as wedge-and-dash drawings, and as Fischer projections in Figure 7.6. Fischer projections are always generated the same way the molecule is oriented so that the vertical bonds at the chirality center are directed away from you and the horizontal bonds point toward you. A projection of the bonds onto the page is a cross. The chirality center lies at the center of the cross but is not explicitly shown. 

The three water ligands located at meridional positions of the J ,J -DBFOX/Ph aqua complexes may be replaced by another molecule of DBFOX/Ph ligand if steric hindrance is negligible. Based on molecular model inspection, the hetero-chiral enantiomer S,S-DBFOX/Ph looks like a candidate to replace the water ligands to form the heterochiral meso-2 l complex J ,J -DBFOX/Ph-S,S-DBFOX/... 

The cyclooctapyrroles shown in Figure 55 appear predestined to form binuclear metal complexes since the loop-shaped conformation of these macrocycles exhibits two structurally identical, helical N4 cavities. Enantiomers of such complexes, which are presumably generally very stable towards racemization owing to the rigidity of the molecule imposed by the incorporation of the metal, are of interest as possible models for binuclear metalloenzymes and as potential catalysts in asymmetric synthesis. The first two ligands as well as their recently obtained palladium complexes601 were... 

The implication of these results is that deposition of, for example, R( +)-crystals on to the racemic films provides a nucleation site for R( + ) -molecules in the film, leaving behind a partially resolved film of predominantly S( — )-molecules. Deposition of S( — (-crystals should, alternatively, leave behind a film composed predominantly of R( + )-molecules. This model is supported by the ESP data obtained on the clean acidic surface, where the free energy of enantiomer crystals appears to be lower compared with liquid-like film states than that of the racemic crystals. 

There are two macroscopic racemates and two conglomerates possible in this model, each conglomerate showing two enantiomers. This situation is quite analogous to the case of a molecule with three tetrahedral stereogenic... 

Examination of Dreiding models showed that 177 is a highly strained and rigid molecule and that only the relative arrangement of groups as in structure 177 or its enantiomer is possible. 

Chiral molecules interact to form complexes that are related as enantiomers or as diastereomers. Enantiomers are perfect chemical models for each other except in their interactions with polarized light or with other chiral molecules, and this provides the basis for an absolute method for demonstrating subtle differences in physical properties that might otherwise be confused with the effects of impurities. 

It is a common understanding that the spatial arrangements of the substituents of a molecule have an crucial effect on whether an enzyme can accept the compound as a substrate. The effect of configuration on the difference of reactivities of enantiomers may be evaluated, as the two enantiomers can be separated and treated as individual starting materials and their products. In fact, promising models of enzyme-substrate interactions have been proposed that permit successful interpretation of the difference of reactivities between a given pair of enantiomers [29,30]. On the other hand, analysis of the reactivity of the conformational isomers of a substrate is rather difficult,because conformers are readily interconvertible under ordinary enzymatic reaction conditions. 

Each isomer is the mirror image of the other and they are known as optical isomers or enantiomers. But all molecules have mirror images, yet they do not all exhibit optical isomerism. What makes lactic acid different is that its two isomers are non-superimposable. You should make molecular models of these optical isomers to convince yourself that one isomer cannot be superimposed on the other. 

The creation of a descriptor that takes into consideration the number of chiral centers, their location in the molecule, and how their handedness affects the bioactivities is needed. Through the use of a descriptor of this nature, when a QSAR program is presented with the correct information (bioactivities for individual enantiomers and correctly constructed molecules), it will be able to construct QSAR models that incorporate chirality. 

Given atomic coordinates for a particular conformation of a molecule and some property value assigned to each atom, one can easily calculate a chirality function that distinguishes enantiomers, is zero for an achiral molecule, and is a continuous function of the coordinates and properties. This is useful as a quantitative measure of chirality for molecular modeling and structure-activity relations. 

In order to stress the distinction between actual molecules and molecules represented as models, the terms enantiomer/c and diastereower/c are only applied to the former, for the latter the correct terms are enantiomorphic and diastereomorphia5. The Morphic nomenclature is also applied when parts of a molecule, e.g.. isolated groups or fragments, are discussed6. 

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