ELECTROCHEMISTRY OF 3,4-DIPHENYL-1,2,5-THIADIAZOLE 1,1-DIOXIDE (I) AND ITS DERIVATIVES IN ETHANOL ACETONITRILE SOLUTIONS AND INTERACTIONS OF THE DIANION OF I WITH METAL-CATIONS

The equilibrium between I and the product resulting from the addition of ethanol to one of its C=N double bonds: 3-ethoxy- 3,4- diphenyl- 1, 2,5-thiadiazoline 1,1-dioxide (II), is studied by electrochemical meth ods in ethanol (EtOH)-acetonitrile (ACN) solvent mixtures. The equilib rium constant is measured and a complete mechanism for the electroredu ction of I and II in ACN solutions containing EtOH is proposed. The vo ltammetric properties of the newly synthesized compound 3-ethoxy- 2- m ethyl- 3,4- diphenyl-1, 2,5-thiadiazoline 1,1-dioxide (IV) are also re ported. A stabilization of the dianion of I by alkali-metal cations, s uch as K+, Na+ and Li+, and divalent cations (Sr2+ and Mg2+) is voltam metrically measured. Equilbrium constants are estimated and compared f or the interaction of I2- and the alkali-metal cations in ACN solution s of I.