The oxidative adsorption of n-alkanethiolates (CncH2nc+1S-, nc = 2-8) at Hg in aqueous solutions containing 0.5 M NaOH is reported. Oxidative adsorption of CncH2nc+1S- is characterized by two voltammetric waves corresponding to the formation of energetically distinct low-density and high-density surface phases of Hg-SCncH2nc+1. The high-density surface phase (9.8 × 10-10 mol/cm2) corresponds to adsorption of ca. one monolayer of CncH2nc+1S-. Electrodeposition of a bulk film of a mercury thiolate complex also occurs at more positive potentials in solutions containing short-chain n-alkanethiolates, nc ≤ 5. The dependence of the adsorption half-wave potential E1/2 on the solution concentration of CncH2nc+1S- indicates that approximately one electron is transferred per adsorbed molecule. The free energy of adsorption ΔGads of CncH2nc+1S- on Hg decreases by ∼1 kcal/mol per nc, reflecting the influence of hydrophobic interactions and intermolecular forces on the thermodynamic stability of the monolayer.