Abstract
3-Mercaptopropanol (R′-SH) and 3-acetyl-3-mercaptopropanol (R″-SH) indicate anodic wave due to electrode reaction of RSH+Hg→RSHg+H+e(pH<pK′) and RS-+Hg→RSHg+e(pH>pK′). The pK′ calculated from the E1/2-pH curve is 9.5 for R′-SH and 7.5 for R″-SH, which agree with the value obtained by titration method. Total wave-height is proportional concentration and to the square root of mercury pressure, and the diffusion current constant is 1.8 for R′-SH and 1.7 for R″-SH.
Bis (3-hydroxypropyl) disulfide (R′-S-S-R′), bis (1-acetyl-3-hydroxypropyl) disulfide (R″SSR″), and dipropyl disulfide (Pr-S-S-Pr) all show two-electron reduction wave to thiol. Its E1/2 is independent of pH and shifts to negative potential with increase of concentration. These thiols and disulfides show adsorption wave. From the area occupied by the adsorbed molecule (25 Å2 for R′-S-Hg and 31 Å2 for R″-S-Hg) calculated from the limit value of this wave height, it is assumed that R′-SHg forms a single molecular layer with the S-Hg bond axis perpendicular to the mercury surface. These substances indicate A. C. polarograms corresponding to the adsorption and regular waves. The wave height and concentration in these cases are in the relation of adsorption isotherm.
