ION ASSOCIATION AND REACTIVITY OF THE ALKALI-METAL SALTS OF ALKANOIC ACIDS IN DIPOLAR APROTIC-SOLVENTS

The effect of added alkali metal perchlorates on the rate of lactonization of ω‐bromoalkanoate ions was investigated in 99% dimethyl sulphoxide (four‐membered ring formation) and in dimethylformamide (DMF) (four‐ and sixteen‐membered ring formation). In all cases the effect of the added metal salts is rate depressing, as a result of the lower reactivity of metal ion‐associated species relative to the free ions. Ion‐pairing association constants were determined, but the reactivity of ion pairs were so low as to elude direct measurement in most cases. Evidence was also obtained for the formation of ion triplets with Li+ in DMF. The relevance of the present results in connection with the ‘caesium effect’ is briefly discussed. Copyright © 1990 John Wiley & Sons Ltd.