Optical superposition
The optical superposition (from Latin super = over ; positio = position , settlement , position ) is a stereochemical principle established by Jacobus Henricus van 't Hoff in 1875 , which states that in optically active compounds with several elements of chirality, each element contributes to the Total rotation value. In the ideal case, the total rotation is equal to the algebraic sum of the contributions made by the individual stereocenters.
Jacobus Henricus van 't Hoff formulated the principle as follows:
"For every active substance the total rotation caused by the same is equal to the algebraic sum of the partial rotations resulting from the individual asymmetric carbon atoms."
The principle is only valid if the rotation value resulting from a stereocenter is independent of the configuration of other stereochemical groups in the molecule. If the stereochemical centers influence each other through intramolecular interactions, the so-called “vicinal effect”, the principle no longer applies strictly. The degree of intramolecular influence depends on the spatial proximity of the stereocenters and becomes smaller with increasing distance.
Individual evidence
- ↑ JH Van't Hoff: "Voorsteel tot uitbriding der tegen woordig in de Scheikunde gebruigte structural formules in de ruimte etc. Utrecht 1874." In: Bull. Soc. chim. France (2) Vol. 23, 1875, pp. 296-338.
- ↑ L. Tschugaeff, A. Glebko: On the knowledge of the optical superposition. In: Reports of the German Chemical Society. 46, 1913, pp. 2752-2762, doi : 10.1002 / cber.19130460346 .
- ^ Karl Freudenberg, Werner Kuhn: Rules and superposition in the optical rotation. In: Reports of the German Chemical Society (A and B Series). 64, 1931, pp. 703-734, doi : 10.1002 / cber.19310640402 .