Ziegler-Ruggli dilution principle
The Ziegler-Ruggli dilution principle (also Ruggli Ziegler principle ) states that an intra -molecular chemical reaction in relation to the inter -molecular reaction at high dilution is preferred because the probability of intermolecular reaction compared to the intramolecular reaction becomes less and less.
It is based on the fact that the probability that the ends of a molecule will find each other (intramolecular reaction) is independent of the concentration of the molecules. However, the probability that two different molecules will collide (intermolecular reaction) decreases with dilution.
Examples of the application of the principle are ring closure reactions of compounds suitably substituted in the α and ω positions, such as in the Thorpe-Ziegler reaction or the Dieckmann condensation . The yields in these ring closure reactions are poor in the production of 9- to 13-membered rings due to the transannular tension . However, they can be improved by working in high dilution. The necessary dilution is expediently not achieved by increasing the volume of the reaction systems, but rather by extremely slow addition of the starting materials to be converted .
The principle was discovered in 1912 by the Swiss chemist Paul Ruggli and further developed systematically by Karl Ziegler in 1933 .
literature
- Mary Eagleson: Concise encyclopedia chemistry. De Gruyter Berlin, New York 1994, ISBN 0-89925-457-8 ( limited preview in Google book search), p. 293.
Individual evidence
- ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 6: T-Z. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1988, ISBN 3-440-04516-1 , p. 4699.