EFFECTS OF ELECTRONEGATIVE SUBSTITUENTS OF ANIONS ON ION-PAIR FORMATION .1. TEMPERATURE-DEPENDENCE OF THE CONDUCTIVITY OF LITHIUM FLUOROACETATE AND ALKALI-METAL ACETATE SOLUTIONS IN DIMETHYL-SULFOXIDE

The effect of electron-withdrawing substituents on ion-ion interaction s is exemplified by conductivity studies on dimethyl sulfoxide solutio ns of lithium acetate and fluoroacetates. Association constants decrea se upon increasing fluorine substitution by a factor of 50. They are c orrelated with mean oxygen charges calculated with the help of semiemp irical quantum mechanical methods. The distance parameters from such c alculations prove to be good estimates for the liquid state. Non-Coulo mbic contributions of the CH3COO- ion to the ion-ion interactions show stronger competition with solvent molecules in the solvation shell of the Li+ ion than the CF3COO- ion, which is a weak ligand in compariso n to the dimethyl sulfoxide molecule.