Ion pair
Ion pairs consisting of a cation R + and an anion X - can appear in different forms in organic chemistry :
- intimate or internal ion pair - also contact ion pair . The ions R + and X - created by a heterolytic bond cleavage remain in close contact with each other ( ion association ) and are usually surrounded by a common solvation shell .
- solvent separated or external ion pair . One or more solvent molecules have one another between R + and X - whereby a mutual electrostatic attraction persists. However, due to the greater distance between R + and X - and the distribution of the charge in the solvation shells, the force of attraction between the cation and the anion is reduced.
- completely solvated ions , which move practically independently of one another as independent particles and more or less obey the laws of diffusion .
Education (examples)
Ion pairs are formed e.g. B. in the course of a monomolecular nucleophilic substitution , ie an S N 1 reaction. The formation of ion pairs in the meantime is also discussed in the Beckmann rearrangement .
Individual evidence
- ^ Ivan Ernest: Binding, Structure and Reaction Mechanisms in Organic Chemistry , Springer-Verlag, 1972, pp. 93–96, ISBN 3-211-81060-9 .
- ^ Siegfried Hauptmann : Organic Chemistry , 2nd revised edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, p. 153, ISBN 3-342-00280-8 .
- ^ Hermann Höver: Reaction Mechanisms of Organic Chemistry , Verlag Chemie - John Wiley & Sons, 1973, pp. 288–289, ISBN 3-527-25442-0 .