The discovery of two kinds of ion pairs

Abstract

ABSTRACT:The discovery and implications of the existence of two kinds of ion pairs in solutions of carbanion salts is described. Also discussed are the factors controlling tight-loose ion pair equilibrium: the nature of the carbanion and its counterion, temperature, pressure, solvent, and cationcomplexing additives. A few examples are presented of the effect of these ionic species on the mechanisms of anionic polymerization and proton transfer.

Applications of NMR diffusion methods with emphasis on ion pairing in inorganic chemistry: a mini‐review

“…Differing types of ion pairs may have relatively unique physical characteristics that allow them to be readily recognized, e.g. it is known that UV spectra for the tight ion pairs of some main group fluorenyl salts are different from those measured from the individual solvent‐separated ions . This is especially true if the equilibrium constant for Eqn is fairly large.…”

“…This is especially true if the equilibrium constant for Eqn is fairly large. A number of physical techniques have been employed to help in the characterization of ion pairs including conductometric, potentiometric, activity and solubility measurements as well as several types of relaxation methods …”

Fundamental Kinetics of Living Anionic Polymerization of Isocyanates Emerging by the Sodium Diphenylmethane-Mediated Initiation

“…The discovery of “living anionic polymerization” by Szwarc − has boosted up the development of high techniques for the access to synthetic polymers with well-controlled lengths, compositions, architectures, and functionalities. − In the meantime, intensive thermodynamic and kinetic analyses have also been made to understand the states and behaviors of anions at the propagating chain ends. − The findings have revealed that the propagation rate relies on the equilibrium of (contact/solvent-separated) ion pairs and the other kinds of species (free ions and self-associated ion pairs). − ,− Because each state of anions leads to the difference in the mechanistic pathway of propagation as well as in the reactivity, − ,− the equilibrium aspect is basically related to the rate law of propagation and even to the level of control over molecular weights (MWs) in many cases. In general, the anionic equilibrium depends on the type of monomer − ,− and shifts by varying the countercation, solvent, temperature, and concentration. − ,…”

Cation Molecular Exchanger Based on a Conformational Hinge

“…Interaction between the potassium cation bound to the crown ether and the picrate anion is expected to be very strong in organic solvents. 40 Therefore, slow addition of Zn 2+ to the potassium complex of 7 should result in a release of the potassium cation together with the picrate anion. This dissociation process should be detected by UV−vis spectroscopy.…”

“…The absorption of the picrate (340–440 nm) is well separated from the absorption of the zinc­(II) complex of the receptor. Interaction between the potassium cation bound to the crown ether and the picrate anion is expected to be very strong in organic solvents . Therefore, slow addition of Zn 2+ to the potassium complex of 7 should result in a release of the potassium cation together with the picrate anion.…”