Homotopic nuclei

It is important to note that enantiotopic nuclei, i.e., nuclei that are related by reflection symmetry, are rendered diastereotopic in a chiral environment. Thus, in contrast to homotopic nuclei, i.c., nuclei that are related by an axis of rotation, isochronous (enantiotopic) nuclei can be transformed into anisochronous (diastereotopic) nuclei via desymmetrization with chiral reagents or in chiral environments. 

Nuclei are chemically equivalent if they can be interchanged by a non-trivial symmetry operation. Nuclei interchangeable by a pure rotation (C , n=2, 3,4,...) are called homotopic. Nuclei related only by a centre (i) of inversion or by a plane ([Pg.7]

Nuclei that are equivalent by virtue of any C axis (n> 1) are said to be homotopic. The hydrogens in 4-1 through 4-5 all fall into this category. A set of homotopic nuclei gives rise to only one NMR signal. 

EXAMPLE 4.6 (a) Indicate all homotopic nuclei, enantiotopic nuclei, and diastereotopic nuclei in structure 4-10. You may assume rapid rotation of all bonds, (b) How many H and 13C NMR signals would you predict for the compound ... 

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