Pseudochiral center

Pseudochiral center, that is, three distinguishable neighbors... 

The terms stereocenter, chirotopic, and achirotopic will be used in this text in line with the most recent terminology. However, other terms are found in the older literature. C was previously referred to as a chiral or pseudochiral center. The term pseudochiral center is based on the same convention used to classify C as achirotopic instead of chirotopic. The terms asymmetric and pseudoasymmetric center are found in much older literature. 

Such carbon atoms are referred to as pseudochiral centers in long-chain polymers because the polymers do not in fact exhibit optical activity (12). The reason for the lack of optical activity can be seen through a closer examination of the substituents on such a pseudochiral center ... 

Answer Optical activity is influenced only by the first few atoms around an asymmetric carbon (C ). For the two sections of the main chain, these will be identical regardless of the length of the whole polymer chain. The carbons marked C in (Xlll) are thus not truly asymmetric and are termed pseudoasymmetric or pseudochiral carbons. Only those C centers near the ends of a polymer molecule will be truly asymmetric, but since there are too few chain ends in a high molecular-weight polymer such centers do not confer any significant optical activity on the molecule as a whole. Polypropylene is thus optically inactive. 

Subsequent work, in fact, showed that it was possible to use racemic monomer — to make the synthesis absolute. The racemic compound was isostructural with crystals of the pure enantiomer, i.e., the chiral crystals (T l) of the racemate consisted of a disordered solid solution of the two enantiomers. Fortunately, the reacting centers were contained within an effectively pseudochiral environment. 

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