Energy-based classification of stereoisomers

The geometry-based classification of stereoisomers, as discussed above, discriminates two mutually exclusive categories, namely enantiomers amd diastereoisomers. 

The configuration-conformation classification of stereoisomers lacks a well defined borderline. In the continuum of energy values, intermediate cases exist which are difficult to classify. In the author s opinion (see also [19]), the boundary between configuration and conformation should be viewed as a broad energy range encompassing the value of 80 kJ/mol (ca. 20 kcal/mol), which is the limit of fair stability under ambient conditions. 

The classification of stereoisomers according to the two independent criteria of symmetry and energy is presented graphically in Fig. 3. Representing all cases of 

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