CRYPTATE ACIDITY SCALES - SOLVENT POLARITY EFFECT ON ION-PAIR AND FREE-ION ACIDITY OF ORGANIC-COMPOUNDS

[2.1.1]Cryptated lithium salts of a wide range of CH-acids were studie d spectrophotometrically and conductimetrically in solvents of low pol arity. 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 stud ied ions at concentrations below 10(-3) mol-1 even in the benzene. The relative equilibrium acidities in benzene, N-methylmorpholine and tet rahydrofuran for a number of CH-adds are reported. Solvent polarity do es not influence the cryptate ion-pair acidity of the investigated com pounds. The relative free ion acidities were calculated for some of th e studied acids in different solvents by combination of the ion-pair a cidity values with the conductimetric data on dissociation constants o f the cryptate ion pairs. A linear relationship between the free ion a cidity and the reciprocal of the dielectric constant was found. An ext rapolation method is suggested for the calculation of gas-phase acidit y from the data obtained in solution.