Term: asymmetric transformation
https://doi.org/10.1351/goldbook.A00485

Definition:
The conversion of a racemate into a pure enantiomer or into a mixture in which one enantiomer is present in excess, or of a diastereoisomeric mixture into a single diastereoisomer or into a mixture in which one diastereoisomer predominates. This is sometimes called deracemization. If the two enantiomers of a chiral substrate A are freely interconvertible and if an equal amount or excess of a non-racemizing second enantiomerically pure chemical species, say (R)-B, is added to a solution of racemic A, then the resulting equilibrium mixture of adducts A·B will, in general, contain unequal amounts of the diastereoisomers (R)-A·(R)-B and (S)-A·(R)-B. The result of this equilibration is called asymmetric transformation of the first kind. If, in such a system, the two diastereoisomeric adducts differ considerably in solubility so that only one of them, say (R)-A·(R)-B, crystallizes from the solution, then the equilibration of diastereoisomers in solution and concurrent crystallization will continue so that all (or most) of the substrate A can be isolated as the crystalline diastereoisomer (R)-A·(R)-B. Such a 'crystallization-induced asymmetric transformation' is called an asymmetric transformation of the second kind.

Related Terms:
1) stereoconvergence (http://doi.org/10.1351/goldbook.S05975).
2) racemate (http://doi.org/10.1351/goldbook.R05025).
3) enantiomer (http://doi.org/10.1351/goldbook.E02069).
4) racemic (http://doi.org/10.1351/goldbook.R05026).
5) diastereoisomers (http://doi.org/10.1351/goldbook.D01679-2).
6) equilibration (http://doi.org/10.1351/goldbook.E02175).
7) asymmetric (http://doi.org/10.1351/goldbook.A00478).
8) transformation (http://doi.org/10.1351/goldbook.T06446).
9) solubility (http://doi.org/10.1351/goldbook.S05740).
10) crystallization (http://doi.org/10.1351/goldbook.C01434).
11) diastereoisomeric (http://doi.org/10.1351/goldbook.D01679-1).
12) chiral (http://doi.org/10.1351/goldbook.C01057).

Source: PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2200 (https://doi.org/10.1351/pac199668122193)

Citation: 'asymmetric transformation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00485

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