Abstract
The reaction of vitamin K3 (I) with some thiol compounds was studied by polarography in 80% ethanol containing acetate buffer and sodium perchlorate. In the absence of' oxygen in solution, thiol compounds react with I to form naphthohydroquinones having a thioether linkage as the result of the addition of SH group at 3-position of naphthoquinone ring in I. The reaction products changed to quinone-thioether compounds by air oxidation with the formation of hydrogen peroxide. The reaction mechanisms were confirmed by e1ectrochemica1 and spectrophotometric measurements of I in the presence of various thiol compounds. The effect of pH on the reaction rate was examined by following the change in the diffusion current of I with time at various pH's. In the case of the I-cysteine (IIg) reaction system, the polarograms were somewhat complicated compared with those obtained with other thiol compounds. These experimental results suggested that the subsequent reaction must be taken into account after the formation of hydroquinone-thioether compound between I and IIg.
