Chiral molecules distinguishing from achiral

The compound has two chirality centres and three pseudo chirality centres. There is however, only one (achiral) diastereomer of the compound shown in the question. The two isomers can be distinguished from one another solely on the relative position of the chlorine or bromine atoms which lie in a plane which also happens to be the plane of symmetry of the molecule (this is the only symmetry element present, therefore the symmetry point group is Cs). It is possible in this instance to specify the configuration unequivocally using the descriptors E and Z. However, in systematic nomenclature the complete configuration of all the stereogenic centres is specified. Thus the (so-called) Z isomer is (ls,3r,5 ,6r,7S)-l,6-dibromo-3,6-dichloroadamantane and the isomer is (ls,3r,5 ,6s,7S)-l,6-dibromo-3,6-dichloroadamantane, i.e. the two isomers can be distinguished simply by the descriptor used for position 6. 

Although the two halves of myoinositol are stereochemically nonequivalent, they are chemically equivalent to an achiral molecule or reagent. In other words, an achiral molecule or reagent does not show preferential selectivity for either side and therefore reacts with both halves at the same rate. However, the biochemical consequence of enantiotopic carbons of most relevance to biochemists is that a chiral molecule, such as an enzyme, can readily distinguish between C-l and C-3 as well as C-4 and C-6 and preferentially reacts with one enantiotopic carbon or another. For example, myo-inositol kinase phosphory-lates myoinositol exclusively at the D-3 position and yields the chiral product, 1 D-myo-inositol-3-monophosphate (15) (Deitz and Albersheim, 1965 Loewus et al., 1982). This is the same isomer produced from glucose-6-phosphate by myo-inositolphosphate synthase (reviewed in Loewus, 1990a). The only route... 

While a pro-chiral molecule is achiral, its two equivalent groups can be distinguished if it interacts with a chiral receptor. This was noted by Alexander Ogston, who explained why the two identical -CH2-COO groups in pro-chiral citrate are distinguished by the enzyme aconitase. One -CH2-COO group of citrate is derived from oxaloacetate, while the... 

The symmetry in molecules helps to distinguish chiral structures from achiral ones... 

How do we use this idea to distinguish a chiral molecule from an achiral one Chiral molecules cannot have a plane of symmetry. For example, the first four methanes in Figure 5-4 are clearly achiral because of the presence of a mirror plane. You will be able to classify most molecules in this book as chiral or achiral simply by identifying the presence or absence of a plane of symmetry. 

Although enantiomers have identical chemical properties in achiral environments, they differ in one important physical property Enantiomers behave differently toward plane-polari2ed light. This difference allows us to distinguish a chiral molecule from its enantiomer in the laboratory. 

Figure 9.18 (a) When a prochiral molecule is held in a chiral environment, the two seemingly identical substituents (red) are distinguishable, (b) Similarly, when an achiral coffee mug is held in the chiral environment of your hand, it s much easier to drink from one side than the other because the two sides of the mug are now distinguishable. 

Problem 5.23 Answer True or False to each of the following statements and explain your choice. ( ) There are two broad classes of stereoisomers, (b) Achiral molecules cannot possess chiral centers, (c) A reaction catalyzed by an enzyme always gives an optically active product, (d) Racemization of an enantiomer must result in the breaking of at least one bond to the chiral center, (e) An attempted resolution can distinguish a racemate from a meso compound. <... 

Hydrolases can distinguish between the two enantiomeric faces of achiral substrates such as enol esters possessing a plane of symmetry within the molecule [25]. The attack of the enzyme s nucleophilic chemical operator predominantly occurs from one side, leading to an unsymmetric enolization of the unstable free enol towards one preferred side within the chiral environment of the enzyme s active site [26]. During the course of the reaction a new center of chirality is created in the product (Scheme 2.2). 

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