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Cryptate acidity scales. Solvent polarity effect on ion‐pair and free ion acidity of organic compounds
Author(s) -
Antipin Igor S.,
Gareyev Roustam F.,
Vedernikov Andrey N.,
Konovalov Alexander I.
Publication year - 1994
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610070404
Subject(s) - chemistry , ion , inorganic chemistry , cryptand , solvent , dissociation (chemistry) , dissociation constant , counterion , tetrahydrofuran , stability constants of complexes , benzene , organic chemistry , biochemistry , receptor
[2.1.1] Cryptated lithium salts of a wide range of CH‐acids were studied spectrophotometrically and conductimetrically in solvents of low polarity. Such salts exist in media of different dielectric constants in the form of cryptand‐separated ion pairs which are identical in their spectral and conductance properties with common solvent‐separated ion pairs. No formation of higher ionic clusters was observed for the studied ions at concentrations below 10 −3 mol −1 even in the benzene. The relative equilibrium acidities in benzene, N ‐methylmorpholine and tetrahydrofuran for a number of CH‐acids are reported. Solvent polarity does not influence the cryptate ion‐pair acidity of the investigated compounds. The relative free ion acidities were calculated for some of the studied acids in different solvents by combination of the ion‐pair acidity values with the conductimetric data on dissociation constants of the cryptate ion pairs. A linear relationship between the free ion acidity and the reciprocal of the dielectric constant was found. An extrapolation method is suggested for the calculation of gas‐phase acidity from the data obtained in solution.