Electrochemical reduction of 2-hydroxypyrimidine in dimethylsulfoxide : Influence of the father-son reaction

Abstract

In DMSO (0.1 M TEAP), 2-hydroxypyrimidine (2-HP) is reversibly reduced (1e process) to a radical anion, whose dimerization is slower than its attack (it is a strong base) on unreduced 2-HP to abstract a proton (father-son reaction), producing the neutral free radical, which dimerizes more rapidly than the radical anion, and the anion of 2-HP, which can be involved in a Hg(I)---Hg(O) couple; the apparent faradaic n is less than one. On addition of strong base to a 2-HP solution, the 2-HP is converted to the anion and the only electrochemical activity seen is that due to the mercury couple. On strong acid addition, the protonated 2-HP formed is more easily reduced than neutral 2-HP; the resulting current considerably exceeds that for 2-HP itself (faradaic n equals one); the anion-mercury reaction couple is not seen. The neutral free radical formed rapidly dimerizes. Weak acid addition produces an adduct due to hydrogen bridging between acid anion and pyrimidine reduction site; reduction to the neutral free radical is facilitated; the weak acid anion is involved in a Hg(I)---Hg(O) couple at a potential characteristic for the acid used; the mercury-pyridimine anion couple occurs at a potential characteristic for 2-HP.