Abstract
Thioacetazone gives 2 steps of 2-electron reduction waves in acid media, which are ascribed to a reductive cleavage of the N-N bond in the protonated thioacetazone and a saturation of the -CH=N- group, respectively. Precedence of the protonation of base on the electrode causes in a kinetic current. In alkaline media, thioacetazone gives other reduction wave due to a 2-electron reduction of the -CH=N- group in the free base, and an anodic wave which are ascribed to the formation of a mercurous complex on the electrode. The reduction waves of benzaldehyde thiosemicarbazone and p-acetamidobenzaldehyde semicarbazone and the first reduction wave of S-methylthioacetazone are also ascribed to the reaction as similar as that of thioacetazone. The second reduction wave of S-methylthioacetazone as well as the reduction waves of S-methylisothiourea and S-ethylisothiosemicarbazide are assumed to be due to the reduction of the RSC=NH group. p-Acetamidobenzaldehyde shows 2 steps of 1-electron reduction waves at pH about 4, which overlap together and diminish at higher pH. Thiosemicarbazides in alkali give and anodic wave due to a reaction with mercurous ion.
